Mode Setting Helper Functions¶
The DRM subsystem aims for a strong separation between core code and helper libraries. Core code takes care of general setup and teardown and decoding userspace requests to kernel internal objects. Everything else is handled by a large set of helper libraries, which can be combined freely to pick and choose for each driver what fits, and avoid shared code where special behaviour is needed.
This distinction between core code and helpers is especially strong in the modesetting code, where there’s a shared userspace ABI for all drivers. This is in contrast to the render side, where pretty much everything (with very few exceptions) can be considered optional helper code.
There are a few areas these helpers can grouped into:
- Helpers to implement modesetting. The important ones here are the atomic helpers. Old drivers still often use the legacy CRTC helpers. They both share the same set of common helper vtables. For really simple drivers (anything that would have been a great fit in the deprecated fbdev subsystem) there’s also the simple display pipe helpers.
- There’s a big pile of helpers for handling outputs. First the generic bridge helpers for handling encoder and transcoder IP blocks. Second the panel helpers for handling panel-related information and logic. Plus then a big set of helpers for the various sink standards (DisplayPort, HDMI, MIPI DSI). Finally there’s also generic helpers for handling output probing, and for dealing with EDIDs.
- The last group of helpers concerns itself with the frontend side of a display pipeline: Planes, handling rectangles for visibility checking and scissoring, flip queues and assorted bits.
Modeset Helper Reference for Common Vtables¶
The DRM mode setting helper functions are common code for drivers to use if they wish. Drivers are not forced to use this code in their implementations but it would be useful if the code they do use at least provides a consistent interface and operation to userspace. Therefore it is highly recommended to use the provided helpers as much as possible.
Because there is only one pointer per modeset object to hold a vfunc table for helper libraries they are by necessity shared among the different helpers.
To make this clear all the helper vtables are pulled together in this location here.
-
struct
drm_crtc_helper_funcs
¶ helper operations for CRTCs
Definition
struct drm_crtc_helper_funcs {
void (*dpms)(struct drm_crtc *crtc, int mode);
void (*prepare)(struct drm_crtc *crtc);
void (*commit)(struct drm_crtc *crtc);
enum drm_mode_status (*mode_valid)(struct drm_crtc *crtc, const struct drm_display_mode *mode);
bool (*mode_fixup)(struct drm_crtc *crtc,const struct drm_display_mode *mode, struct drm_display_mode *adjusted_mode);
int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,struct drm_display_mode *adjusted_mode, int x, int y, struct drm_framebuffer *old_fb);
void (*mode_set_nofb)(struct drm_crtc *crtc);
int (*mode_set_base)(struct drm_crtc *crtc, int x, int y, struct drm_framebuffer *old_fb);
int (*mode_set_base_atomic)(struct drm_crtc *crtc,struct drm_framebuffer *fb, int x, int y, enum mode_set_atomic);
void (*disable)(struct drm_crtc *crtc);
int (*atomic_check)(struct drm_crtc *crtc, struct drm_atomic_state *state);
void (*atomic_begin)(struct drm_crtc *crtc, struct drm_atomic_state *state);
void (*atomic_flush)(struct drm_crtc *crtc, struct drm_atomic_state *state);
void (*atomic_enable)(struct drm_crtc *crtc, struct drm_atomic_state *state);
void (*atomic_disable)(struct drm_crtc *crtc, struct drm_atomic_state *state);
bool (*get_scanout_position)(struct drm_crtc *crtc,bool in_vblank_irq, int *vpos, int *hpos,ktime_t *stime, ktime_t *etime, const struct drm_display_mode *mode);
};
Members
dpms
Callback to control power levels on the CRTC. If the mode passed in is unsupported, the provider must use the next lowest power level. This is used by the legacy CRTC helpers to implement DPMS functionality in
drm_helper_connector_dpms()
.This callback is also used to disable a CRTC by calling it with DRM_MODE_DPMS_OFF if the disable hook isn’t used.
This callback is used by the legacy CRTC helpers. Atomic helpers also support using this hook for enabling and disabling a CRTC to facilitate transitions to atomic, but it is deprecated. Instead atomic_enable and atomic_disable should be used.
prepare
This callback should prepare the CRTC for a subsequent modeset, which in practice means the driver should disable the CRTC if it is running. Most drivers ended up implementing this by calling their dpms hook with DRM_MODE_DPMS_OFF.
This callback is used by the legacy CRTC helpers. Atomic helpers also support using this hook for disabling a CRTC to facilitate transitions to atomic, but it is deprecated. Instead atomic_disable should be used.
commit
This callback should commit the new mode on the CRTC after a modeset, which in practice means the driver should enable the CRTC. Most drivers ended up implementing this by calling their dpms hook with DRM_MODE_DPMS_ON.
This callback is used by the legacy CRTC helpers. Atomic helpers also support using this hook for enabling a CRTC to facilitate transitions to atomic, but it is deprecated. Instead atomic_enable should be used.
mode_valid
This callback is used to check if a specific mode is valid in this crtc. This should be implemented if the crtc has some sort of restriction in the modes it can display. For example, a given crtc may be responsible to set a clock value. If the clock can not produce all the values for the available modes then this callback can be used to restrict the number of modes to only the ones that can be displayed.
This hook is used by the probe helpers to filter the mode list in
drm_helper_probe_single_connector_modes()
, and it is used by the atomic helpers to validate modes supplied by userspace indrm_atomic_helper_check_modeset()
.This function is optional.
NOTE:
Since this function is both called from the check phase of an atomic commit, and the mode validation in the probe paths it is not allowed to look at anything else but the passed-in mode, and validate it against configuration-invariant hardward constraints. Any further limits which depend upon the configuration can only be checked in mode_fixup or atomic_check.
RETURNS:
drm_mode_status Enum
mode_fixup
This callback is used to validate a mode. The parameter mode is the display mode that userspace requested, adjusted_mode is the mode the encoders need to be fed with. Note that this is the inverse semantics of the meaning for the
drm_encoder
anddrm_bridge_funcs.mode_fixup
vfunc. If the CRTC cannot support the requested conversion from mode to adjusted_mode it should reject the modeset. See alsodrm_crtc_state.adjusted_mode
for more details.This function is used by both legacy CRTC helpers and atomic helpers. With atomic helpers it is optional.
NOTE:
This function is called in the check phase of atomic modesets, which can be aborted for any reason (including on userspace’s request to just check whether a configuration would be possible). Atomic drivers MUST NOT touch any persistent state (hardware or software) or data structures except the passed in adjusted_mode parameter.
This is in contrast to the legacy CRTC helpers where this was allowed.
Atomic drivers which need to inspect and adjust more state should instead use the atomic_check callback, but note that they’re not perfectly equivalent: mode_valid is called from
drm_atomic_helper_check_modeset()
, but atomic_check is called fromdrm_atomic_helper_check_planes()
, because originally it was meant for plane update checks only.Also beware that userspace can request its own custom modes, neither core nor helpers filter modes to the list of probe modes reported by the GETCONNECTOR IOCTL and stored in
drm_connector.modes
. To ensure that modes are filtered consistently put any CRTC constraints and limits checks into mode_valid.RETURNS:
True if an acceptable configuration is possible, false if the modeset operation should be rejected.
mode_set
This callback is used by the legacy CRTC helpers to set a new mode, position and framebuffer. Since it ties the primary plane to every mode change it is incompatible with universal plane support. And since it can’t update other planes it’s incompatible with atomic modeset support.
This callback is only used by CRTC helpers and deprecated.
RETURNS:
0 on success or a negative error code on failure.
mode_set_nofb
This callback is used to update the display mode of a CRTC without changing anything of the primary plane configuration. This fits the requirement of atomic and hence is used by the atomic helpers. It is also used by the transitional plane helpers to implement a mode_set hook in drm_helper_crtc_mode_set().
Note that the display pipe is completely off when this function is called. Atomic drivers which need hardware to be running before they program the new display mode (e.g. because they implement runtime PM) should not use this hook. This is because the helper library calls this hook only once per mode change and not every time the display pipeline is suspended using either DPMS or the new “ACTIVE” property. Which means register values set in this callback might get reset when the CRTC is suspended, but not restored. Such drivers should instead move all their CRTC setup into the atomic_enable callback.
This callback is optional.
mode_set_base
This callback is used by the legacy CRTC helpers to set a new framebuffer and scanout position. It is optional and used as an optimized fast-path instead of a full mode set operation with all the resulting flickering. If it is not present
drm_crtc_helper_set_config()
will fall back to a full modeset, using the mode_set callback. Since it can’t update other planes it’s incompatible with atomic modeset support.This callback is only used by the CRTC helpers and deprecated.
RETURNS:
0 on success or a negative error code on failure.
mode_set_base_atomic
This callback is used by the fbdev helpers to set a new framebuffer and scanout without sleeping, i.e. from an atomic calling context. It is only used to implement kgdb support.
This callback is optional and only needed for kgdb support in the fbdev helpers.
RETURNS:
0 on success or a negative error code on failure.
disable
This callback should be used to disable the CRTC. With the atomic drivers it is called after all encoders connected to this CRTC have been shut off already using their own
drm_encoder_helper_funcs.disable
hook. If that sequence is too simple drivers can just add their own hooks and call it from this CRTC callback here by looping over all encoders connected to it using for_each_encoder_on_crtc().This hook is used both by legacy CRTC helpers and atomic helpers. Atomic drivers don’t need to implement it if there’s no need to disable anything at the CRTC level. To ensure that runtime PM handling (using either DPMS or the new “ACTIVE” property) works disable must be the inverse of atomic_enable for atomic drivers. Atomic drivers should consider to use atomic_disable instead of this one.
NOTE:
With legacy CRTC helpers there’s a big semantic difference between disable and other hooks (like prepare or dpms) used to shut down a CRTC: disable is only called when also logically disabling the display pipeline and needs to release any resources acquired in mode_set (like shared PLLs, or again release pinned framebuffers).
Therefore disable must be the inverse of mode_set plus commit for drivers still using legacy CRTC helpers, which is different from the rules under atomic.
atomic_check
Drivers should check plane-update related CRTC constraints in this hook. They can also check mode related limitations but need to be aware of the calling order, since this hook is used by
drm_atomic_helper_check_planes()
whereas the preparations needed to check output routing and the display mode is done indrm_atomic_helper_check_modeset()
. Therefore drivers that want to check output routing and display mode constraints in this callback must ensure thatdrm_atomic_helper_check_modeset()
has been called beforehand. This is calling order used by the default helper implementation indrm_atomic_helper_check()
.When using
drm_atomic_helper_check_planes()
this hook is called after thedrm_plane_helper_funcs.atomic_check
hook for planes, which allows drivers to assign shared resources requested by planes in this callback here. For more complicated dependencies the driver can call the provided check helpers multiple times until the computed state has a final configuration and everything has been checked.This function is also allowed to inspect any other object’s state and can add more state objects to the atomic commit if needed. Care must be taken though to ensure that state check and compute functions for these added states are all called, and derived state in other objects all updated. Again the recommendation is to just call check helpers until a maximal configuration is reached.
This callback is used by the atomic modeset helpers and by the transitional plane helpers, but it is optional.
NOTE:
This function is called in the check phase of an atomic update. The driver is not allowed to change anything outside of the free-standing state object passed-in.
Also beware that userspace can request its own custom modes, neither core nor helpers filter modes to the list of probe modes reported by the GETCONNECTOR IOCTL and stored in
drm_connector.modes
. To ensure that modes are filtered consistently put any CRTC constraints and limits checks into mode_valid.RETURNS:
0 on success, -EINVAL if the state or the transition can’t be supported, -ENOMEM on memory allocation failure and -EDEADLK if an attempt to obtain another state object ran into a
drm_modeset_lock
deadlock.atomic_begin
Drivers should prepare for an atomic update of multiple planes on a CRTC in this hook. Depending upon hardware this might be vblank evasion, blocking updates by setting bits or doing preparatory work for e.g. manual update display.
This hook is called before any plane commit functions are called.
Note that the power state of the display pipe when this function is called depends upon the exact helpers and calling sequence the driver has picked. See
drm_atomic_helper_commit_planes()
for a discussion of the tradeoffs and variants of plane commit helpers.This callback is used by the atomic modeset helpers and by the transitional plane helpers, but it is optional.
atomic_flush
Drivers should finalize an atomic update of multiple planes on a CRTC in this hook. Depending upon hardware this might include checking that vblank evasion was successful, unblocking updates by setting bits or setting the GO bit to flush out all updates.
Simple hardware or hardware with special requirements can commit and flush out all updates for all planes from this hook and forgo all the other commit hooks for plane updates.
This hook is called after any plane commit functions are called.
Note that the power state of the display pipe when this function is called depends upon the exact helpers and calling sequence the driver has picked. See
drm_atomic_helper_commit_planes()
for a discussion of the tradeoffs and variants of plane commit helpers.This callback is used by the atomic modeset helpers and by the transitional plane helpers, but it is optional.
atomic_enable
This callback should be used to enable the CRTC. With the atomic drivers it is called before all encoders connected to this CRTC are enabled through the encoder’s own
drm_encoder_helper_funcs.enable
hook. If that sequence is too simple drivers can just add their own hooks and call it from this CRTC callback here by looping over all encoders connected to it using for_each_encoder_on_crtc().This hook is used only by atomic helpers, for symmetry with atomic_disable. Atomic drivers don’t need to implement it if there’s no need to enable anything at the CRTC level. To ensure that runtime PM handling (using either DPMS or the new “ACTIVE” property) works atomic_enable must be the inverse of atomic_disable for atomic drivers.
This function is optional.
atomic_disable
This callback should be used to disable the CRTC. With the atomic drivers it is called after all encoders connected to this CRTC have been shut off already using their own
drm_encoder_helper_funcs.disable
hook. If that sequence is too simple drivers can just add their own hooks and call it from this CRTC callback here by looping over all encoders connected to it using for_each_encoder_on_crtc().This hook is used only by atomic helpers. Atomic drivers don’t need to implement it if there’s no need to disable anything at the CRTC level.
This function is optional.
get_scanout_position
Called by vblank timestamping code.
Returns the current display scanout position from a CRTC and an optional accurate
ktime_get()
timestamp of when the position was measured. Note that this is a helper callback which is only used if a driver usesdrm_crtc_vblank_helper_get_vblank_timestamp()
for the drm_crtc_funcs.get_vblank_timestamp callback.Parameters:
- crtc:
- The CRTC.
- in_vblank_irq:
- True when called from
drm_crtc_handle_vblank()
. Some drivers need to apply some workarounds for gpu-specific vblank irq quirks if the flag is set. - vpos:
- Target location for current vertical scanout position.
- hpos:
- Target location for current horizontal scanout position.
- stime:
- Target location for timestamp taken immediately before scanout position query. Can be NULL to skip timestamp.
- etime:
- Target location for timestamp taken immediately after scanout position query. Can be NULL to skip timestamp.
- mode:
- Current display timings.
Returns vpos as a positive number while in active scanout area. Returns vpos as a negative number inside vblank, counting the number of scanlines to go until end of vblank, e.g., -1 means “one scanline until start of active scanout / end of vblank.”
Returns:
True on success, false if a reliable scanout position counter could not be read out.
Description
These hooks are used by the legacy CRTC helpers, the transitional plane helpers and the new atomic modesetting helpers.
-
void
drm_crtc_helper_add
(struct drm_crtc *crtc, const struct drm_crtc_helper_funcs *funcs)¶ sets the helper vtable for a crtc
Parameters
struct drm_crtc *crtc
- DRM CRTC
const struct drm_crtc_helper_funcs *funcs
- helper vtable to set for crtc
-
struct
drm_encoder_helper_funcs
¶ helper operations for encoders
Definition
struct drm_encoder_helper_funcs {
void (*dpms)(struct drm_encoder *encoder, int mode);
enum drm_mode_status (*mode_valid)(struct drm_encoder *crtc, const struct drm_display_mode *mode);
bool (*mode_fixup)(struct drm_encoder *encoder,const struct drm_display_mode *mode, struct drm_display_mode *adjusted_mode);
void (*prepare)(struct drm_encoder *encoder);
void (*commit)(struct drm_encoder *encoder);
void (*mode_set)(struct drm_encoder *encoder,struct drm_display_mode *mode, struct drm_display_mode *adjusted_mode);
void (*atomic_mode_set)(struct drm_encoder *encoder,struct drm_crtc_state *crtc_state, struct drm_connector_state *conn_state);
enum drm_connector_status (*detect)(struct drm_encoder *encoder, struct drm_connector *connector);
void (*atomic_disable)(struct drm_encoder *encoder, struct drm_atomic_state *state);
void (*atomic_enable)(struct drm_encoder *encoder, struct drm_atomic_state *state);
void (*disable)(struct drm_encoder *encoder);
void (*enable)(struct drm_encoder *encoder);
int (*atomic_check)(struct drm_encoder *encoder,struct drm_crtc_state *crtc_state, struct drm_connector_state *conn_state);
};
Members
dpms
Callback to control power levels on the encoder. If the mode passed in is unsupported, the provider must use the next lowest power level. This is used by the legacy encoder helpers to implement DPMS functionality in
drm_helper_connector_dpms()
.This callback is also used to disable an encoder by calling it with DRM_MODE_DPMS_OFF if the disable hook isn’t used.
This callback is used by the legacy CRTC helpers. Atomic helpers also support using this hook for enabling and disabling an encoder to facilitate transitions to atomic, but it is deprecated. Instead enable and disable should be used.
mode_valid
This callback is used to check if a specific mode is valid in this encoder. This should be implemented if the encoder has some sort of restriction in the modes it can display. For example, a given encoder may be responsible to set a clock value. If the clock can not produce all the values for the available modes then this callback can be used to restrict the number of modes to only the ones that can be displayed.
This hook is used by the probe helpers to filter the mode list in
drm_helper_probe_single_connector_modes()
, and it is used by the atomic helpers to validate modes supplied by userspace indrm_atomic_helper_check_modeset()
.This function is optional.
NOTE:
Since this function is both called from the check phase of an atomic commit, and the mode validation in the probe paths it is not allowed to look at anything else but the passed-in mode, and validate it against configuration-invariant hardward constraints. Any further limits which depend upon the configuration can only be checked in mode_fixup or atomic_check.
RETURNS:
drm_mode_status Enum
mode_fixup
This callback is used to validate and adjust a mode. The parameter mode is the display mode that should be fed to the next element in the display chain, either the final
drm_connector
or adrm_bridge
. The parameter adjusted_mode is the input mode the encoder requires. It can be modified by this callback and does not need to match mode. See alsodrm_crtc_state.adjusted_mode
for more details.This function is used by both legacy CRTC helpers and atomic helpers. This hook is optional.
NOTE:
This function is called in the check phase of atomic modesets, which can be aborted for any reason (including on userspace’s request to just check whether a configuration would be possible). Atomic drivers MUST NOT touch any persistent state (hardware or software) or data structures except the passed in adjusted_mode parameter.
This is in contrast to the legacy CRTC helpers where this was allowed.
Atomic drivers which need to inspect and adjust more state should instead use the atomic_check callback. If atomic_check is used, this hook isn’t called since atomic_check allows a strict superset of the functionality of mode_fixup.
Also beware that userspace can request its own custom modes, neither core nor helpers filter modes to the list of probe modes reported by the GETCONNECTOR IOCTL and stored in
drm_connector.modes
. To ensure that modes are filtered consistently put any encoder constraints and limits checks into mode_valid.RETURNS:
True if an acceptable configuration is possible, false if the modeset operation should be rejected.
prepare
This callback should prepare the encoder for a subsequent modeset, which in practice means the driver should disable the encoder if it is running. Most drivers ended up implementing this by calling their dpms hook with DRM_MODE_DPMS_OFF.
This callback is used by the legacy CRTC helpers. Atomic helpers also support using this hook for disabling an encoder to facilitate transitions to atomic, but it is deprecated. Instead disable should be used.
commit
This callback should commit the new mode on the encoder after a modeset, which in practice means the driver should enable the encoder. Most drivers ended up implementing this by calling their dpms hook with DRM_MODE_DPMS_ON.
This callback is used by the legacy CRTC helpers. Atomic helpers also support using this hook for enabling an encoder to facilitate transitions to atomic, but it is deprecated. Instead enable should be used.
mode_set
This callback is used to update the display mode of an encoder.
Note that the display pipe is completely off when this function is called. Drivers which need hardware to be running before they program the new display mode (because they implement runtime PM) should not use this hook, because the helper library calls it only once and not every time the display pipeline is suspend using either DPMS or the new “ACTIVE” property. Such drivers should instead move all their encoder setup into the enable callback.
This callback is used both by the legacy CRTC helpers and the atomic modeset helpers. It is optional in the atomic helpers.
NOTE:
If the driver uses the atomic modeset helpers and needs to inspect the connector state or connector display info during mode setting, atomic_mode_set can be used instead.
atomic_mode_set
This callback is used to update the display mode of an encoder.
Note that the display pipe is completely off when this function is called. Drivers which need hardware to be running before they program the new display mode (because they implement runtime PM) should not use this hook, because the helper library calls it only once and not every time the display pipeline is suspended using either DPMS or the new “ACTIVE” property. Such drivers should instead move all their encoder setup into the enable callback.
This callback is used by the atomic modeset helpers in place of the mode_set callback, if set by the driver. It is optional and should be used instead of mode_set if the driver needs to inspect the connector state or display info, since there is no direct way to go from the encoder to the current connector.
detect
This callback can be used by drivers who want to do detection on the encoder object instead of in connector functions.
It is not used by any helper and therefore has purely driver-specific semantics. New drivers shouldn’t use this and instead just implement their own private callbacks.
FIXME:
This should just be converted into a pile of driver vfuncs. Currently radeon, amdgpu and nouveau are using it.
atomic_disable
This callback should be used to disable the encoder. With the atomic drivers it is called before this encoder’s CRTC has been shut off using their own
drm_crtc_helper_funcs.atomic_disable
hook. If that sequence is too simple drivers can just add their own driver private encoder hooks and call them from CRTC’s callback by looping over all encoders connected to it using for_each_encoder_on_crtc().This callback is a variant of disable that provides the atomic state to the driver. If atomic_disable is implemented, disable is not called by the helpers.
This hook is only used by atomic helpers. Atomic drivers don’t need to implement it if there’s no need to disable anything at the encoder level. To ensure that runtime PM handling (using either DPMS or the new “ACTIVE” property) works atomic_disable must be the inverse of atomic_enable.
atomic_enable
This callback should be used to enable the encoder. It is called after this encoder’s CRTC has been enabled using their own
drm_crtc_helper_funcs.atomic_enable
hook. If that sequence is too simple drivers can just add their own driver private encoder hooks and call them from CRTC’s callback by looping over all encoders connected to it using for_each_encoder_on_crtc().This callback is a variant of enable that provides the atomic state to the driver. If atomic_enable is implemented, enable is not called by the helpers.
This hook is only used by atomic helpers, it is the opposite of atomic_disable. Atomic drivers don’t need to implement it if there’s no need to enable anything at the encoder level. To ensure that runtime PM handling works atomic_enable must be the inverse of atomic_disable.
disable
This callback should be used to disable the encoder. With the atomic drivers it is called before this encoder’s CRTC has been shut off using their own
drm_crtc_helper_funcs.disable
hook. If that sequence is too simple drivers can just add their own driver private encoder hooks and call them from CRTC’s callback by looping over all encoders connected to it using for_each_encoder_on_crtc().This hook is used both by legacy CRTC helpers and atomic helpers. Atomic drivers don’t need to implement it if there’s no need to disable anything at the encoder level. To ensure that runtime PM handling (using either DPMS or the new “ACTIVE” property) works disable must be the inverse of enable for atomic drivers.
For atomic drivers also consider atomic_disable and save yourself from having to read the NOTE below!
NOTE:
With legacy CRTC helpers there’s a big semantic difference between disable and other hooks (like prepare or dpms) used to shut down a encoder: disable is only called when also logically disabling the display pipeline and needs to release any resources acquired in mode_set (like shared PLLs, or again release pinned framebuffers).
Therefore disable must be the inverse of mode_set plus commit for drivers still using legacy CRTC helpers, which is different from the rules under atomic.
enable
This callback should be used to enable the encoder. With the atomic drivers it is called after this encoder’s CRTC has been enabled using their own
drm_crtc_helper_funcs.enable
hook. If that sequence is too simple drivers can just add their own driver private encoder hooks and call them from CRTC’s callback by looping over all encoders connected to it using for_each_encoder_on_crtc().This hook is only used by atomic helpers, it is the opposite of disable. Atomic drivers don’t need to implement it if there’s no need to enable anything at the encoder level. To ensure that runtime PM handling (using either DPMS or the new “ACTIVE” property) works enable must be the inverse of disable for atomic drivers.
atomic_check
This callback is used to validate encoder state for atomic drivers. Since the encoder is the object connecting the CRTC and connector it gets passed both states, to be able to validate interactions and update the CRTC to match what the encoder needs for the requested connector.
Since this provides a strict superset of the functionality of mode_fixup (the requested and adjusted modes are both available through the passed in
struct drm_crtc_state
) mode_fixup is not called when atomic_check is implemented.This function is used by the atomic helpers, but it is optional.
NOTE:
This function is called in the check phase of an atomic update. The driver is not allowed to change anything outside of the free-standing state objects passed-in or assembled in the overall
drm_atomic_state
update tracking structure.Also beware that userspace can request its own custom modes, neither core nor helpers filter modes to the list of probe modes reported by the GETCONNECTOR IOCTL and stored in
drm_connector.modes
. To ensure that modes are filtered consistently put any encoder constraints and limits checks into mode_valid.RETURNS:
0 on success, -EINVAL if the state or the transition can’t be supported, -ENOMEM on memory allocation failure and -EDEADLK if an attempt to obtain another state object ran into a
drm_modeset_lock
deadlock.
Description
These hooks are used by the legacy CRTC helpers, the transitional plane helpers and the new atomic modesetting helpers.
-
void
drm_encoder_helper_add
(struct drm_encoder *encoder, const struct drm_encoder_helper_funcs *funcs)¶ sets the helper vtable for an encoder
Parameters
struct drm_encoder *encoder
- DRM encoder
const struct drm_encoder_helper_funcs *funcs
- helper vtable to set for encoder
-
struct
drm_connector_helper_funcs
¶ helper operations for connectors
Definition
struct drm_connector_helper_funcs {
int (*get_modes)(struct drm_connector *connector);
int (*detect_ctx)(struct drm_connector *connector,struct drm_modeset_acquire_ctx *ctx, bool force);
enum drm_mode_status (*mode_valid)(struct drm_connector *connector, struct drm_display_mode *mode);
int (*mode_valid_ctx)(struct drm_connector *connector,struct drm_display_mode *mode,struct drm_modeset_acquire_ctx *ctx, enum drm_mode_status *status);
struct drm_encoder *(*best_encoder)(struct drm_connector *connector);
struct drm_encoder *(*atomic_best_encoder)(struct drm_connector *connector, struct drm_atomic_state *state);
int (*atomic_check)(struct drm_connector *connector, struct drm_atomic_state *state);
void (*atomic_commit)(struct drm_connector *connector, struct drm_atomic_state *state);
int (*prepare_writeback_job)(struct drm_writeback_connector *connector, struct drm_writeback_job *job);
void (*cleanup_writeback_job)(struct drm_writeback_connector *connector, struct drm_writeback_job *job);
};
Members
get_modes
This function should fill in all modes currently valid for the sink into the
drm_connector.probed_modes
list. It should also update the EDID property by callingdrm_connector_update_edid_property()
.The usual way to implement this is to cache the EDID retrieved in the probe callback somewhere in the driver-private connector structure. In this function drivers then parse the modes in the EDID and add them by calling
drm_add_edid_modes()
. But connectors that driver a fixed panel can also manually add specific modes usingdrm_mode_probed_add()
. Drivers which manually add modes should also make sure that thedrm_connector.display_info
,drm_connector.width_mm
anddrm_connector.height_mm
fields are filled in.Virtual drivers that just want some standard VESA mode with a given resolution can call
drm_add_modes_noedid()
, and mark the preferred one usingdrm_set_preferred_mode()
.This function is only called after the detect hook has indicated that a sink is connected and when the EDID isn’t overridden through sysfs or the kernel commandline.
This callback is used by the probe helpers in e.g.
drm_helper_probe_single_connector_modes()
.To avoid races with concurrent connector state updates, the helper libraries always call this with the
drm_mode_config.connection_mutex
held. Because of this it’s safe to inspectdrm_connector->state
.RETURNS:
The number of modes added by calling
drm_mode_probed_add()
.detect_ctx
Check to see if anything is attached to the connector. The parameter force is set to false whilst polling, true when checking the connector due to a user request. force can be used by the driver to avoid expensive, destructive operations during automated probing.
This callback is optional, if not implemented the connector will be considered as always being attached.
This is the atomic version of
drm_connector_funcs.detect
.To avoid races against concurrent connector state updates, the helper libraries always call this with ctx set to a valid context, and
drm_mode_config.connection_mutex
will always be locked with the ctx parameter set to this ctx. This allows taking additional locks as required.RETURNS:
drm_connector_status
indicating the connector’s status, or the error code returned bydrm_modeset_lock()
, -EDEADLK.mode_valid
Callback to validate a mode for a connector, irrespective of the specific display configuration.
This callback is used by the probe helpers to filter the mode list (which is usually derived from the EDID data block from the sink). See e.g.
drm_helper_probe_single_connector_modes()
.This function is optional.
NOTE:
This only filters the mode list supplied to userspace in the GETCONNECTOR IOCTL. Compared to
drm_encoder_helper_funcs.mode_valid
,drm_crtc_helper_funcs.mode_valid
anddrm_bridge_funcs.mode_valid
, which are also called by the atomic helpers fromdrm_atomic_helper_check_modeset()
. This allows userspace to force and ignore sink constraint (like the pixel clock limits in the screen’s EDID), which is useful for e.g. testing, or working around a broken EDID. Any source hardware constraint (which always need to be enforced) therefore should be checked in one of the above callbacks, and not this one here.To avoid races with concurrent connector state updates, the helper libraries always call this with the
drm_mode_config.connection_mutex
held. Because of this it’s safe to inspectdrm_connector->state
.RETURNS:
Either
drm_mode_status.MODE_OK
or one of the failure reasons inenum drm_mode_status
.mode_valid_ctx
Callback to validate a mode for a connector, irrespective of the specific display configuration.
This callback is used by the probe helpers to filter the mode list (which is usually derived from the EDID data block from the sink). See e.g.
drm_helper_probe_single_connector_modes()
.This function is optional, and is the atomic version of
drm_connector_helper_funcs.mode_valid
.To allow for accessing the atomic state of modesetting objects, the helper libraries always call this with ctx set to a valid context, and
drm_mode_config.connection_mutex
will always be locked with the ctx parameter set to ctx. This allows for taking additional locks as required.Even though additional locks may be acquired, this callback is still expected not to take any constraints into account which would be influenced by the currently set display state - such constraints should be handled in the driver’s atomic check. For example, if a connector shares display bandwidth with other connectors then it would be ok to validate the minimum bandwidth requirement of a mode against the maximum possible bandwidth of the connector. But it wouldn’t be ok to take the current bandwidth usage of other connectors into account, as this would change depending on the display state.
Returns: 0 if
drm_connector_helper_funcs.mode_valid_ctx
succeeded and wrote theenum drm_mode_status
value to status, or a negative error code otherwise.best_encoder
This function should select the best encoder for the given connector.
This function is used by both the atomic helpers (in the
drm_atomic_helper_check_modeset()
function) and in the legacy CRTC helpers.NOTE:
In atomic drivers this function is called in the check phase of an atomic update. The driver is not allowed to change or inspect anything outside of arguments passed-in. Atomic drivers which need to inspect dynamic configuration state should instead use atomic_best_encoder.
You can leave this function to NULL if the connector is only attached to a single encoder. In this case, the core will call drm_connector_get_single_encoder() for you.
RETURNS:
Encoder that should be used for the given connector and connector state, or NULL if no suitable encoder exists. Note that the helpers will ensure that encoders aren’t used twice, drivers should not check for this.
atomic_best_encoder
This is the atomic version of best_encoder for atomic drivers which need to select the best encoder depending upon the desired configuration and can’t select it statically.
This function is used by
drm_atomic_helper_check_modeset()
. If it is not implemented, the core will fallback to best_encoder (or drm_connector_get_single_encoder() if best_encoder is NULL).NOTE:
This function is called in the check phase of an atomic update. The driver is not allowed to change anything outside of the
drm_atomic_state
update tracking structure passed in.RETURNS:
Encoder that should be used for the given connector and connector state, or NULL if no suitable encoder exists. Note that the helpers will ensure that encoders aren’t used twice, drivers should not check for this.
atomic_check
This hook is used to validate connector state. This function is called from
drm_atomic_helper_check_modeset
, and is called when a connector property is set, or a modeset on the crtc is forced.Because
drm_atomic_helper_check_modeset
may be called multiple times, this function should handle being called multiple times as well.This function is also allowed to inspect any other object’s state and can add more state objects to the atomic commit if needed. Care must be taken though to ensure that state check and compute functions for these added states are all called, and derived state in other objects all updated. Again the recommendation is to just call check helpers until a maximal configuration is reached.
NOTE:
This function is called in the check phase of an atomic update. The driver is not allowed to change anything outside of the free-standing state objects passed-in or assembled in the overall
drm_atomic_state
update tracking structure.RETURNS:
0 on success, -EINVAL if the state or the transition can’t be supported, -ENOMEM on memory allocation failure and -EDEADLK if an attempt to obtain another state object ran into a
drm_modeset_lock
deadlock.atomic_commit
This hook is to be used by drivers implementing writeback connectors that need a point when to commit the writeback job to the hardware. The writeback_job to commit is available in the new connector state, in
drm_connector_state.writeback_job
.This hook is optional.
This callback is used by the atomic modeset helpers.
prepare_writeback_job
As writeback jobs contain a framebuffer, drivers may need to prepare and clean them up the same way they can prepare and clean up framebuffers for planes. This optional connector operation is used to support the preparation of writeback jobs. The job prepare operation is called from
drm_atomic_helper_prepare_planes()
for structdrm_writeback_connector
connectors only.This operation is optional.
This callback is used by the atomic modeset helpers.
cleanup_writeback_job
This optional connector operation is used to support the cleanup of writeback jobs. The job cleanup operation is called from the existing drm_writeback_cleanup_job() function, invoked both when destroying the job as part of an aborted commit, or when the job completes.
This operation is optional.
This callback is used by the atomic modeset helpers.
Description
These functions are used by the atomic and legacy modeset helpers and by the probe helpers.
-
void
drm_connector_helper_add
(struct drm_connector *connector, const struct drm_connector_helper_funcs *funcs)¶ sets the helper vtable for a connector
Parameters
struct drm_connector *connector
- DRM connector
const struct drm_connector_helper_funcs *funcs
- helper vtable to set for connector
-
struct
drm_plane_helper_funcs
¶ helper operations for planes
Definition
struct drm_plane_helper_funcs {
int (*prepare_fb)(struct drm_plane *plane, struct drm_plane_state *new_state);
void (*cleanup_fb)(struct drm_plane *plane, struct drm_plane_state *old_state);
int (*atomic_check)(struct drm_plane *plane, struct drm_plane_state *state);
void (*atomic_update)(struct drm_plane *plane, struct drm_plane_state *old_state);
void (*atomic_disable)(struct drm_plane *plane, struct drm_plane_state *old_state);
int (*atomic_async_check)(struct drm_plane *plane, struct drm_plane_state *state);
void (*atomic_async_update)(struct drm_plane *plane, struct drm_plane_state *new_state);
};
Members
prepare_fb
This hook is to prepare a framebuffer for scanout by e.g. pinning its backing storage or relocating it into a contiguous block of VRAM. Other possible preparatory work includes flushing caches.
This function must not block for outstanding rendering, since it is called in the context of the atomic IOCTL even for async commits to be able to return any errors to userspace. Instead the recommended way is to fill out the
drm_plane_state.fence
of the passed-indrm_plane_state
. If the driver doesn’t support native fences then equivalent functionality should be implemented through private members in the plane structure.Drivers which always have their buffers pinned should use
drm_gem_fb_prepare_fb()
for this hook.The helpers will call cleanup_fb with matching arguments for every successful call to this hook.
This callback is used by the atomic modeset helpers and by the transitional plane helpers, but it is optional.
RETURNS:
0 on success or one of the following negative error codes allowed by the
drm_mode_config_funcs.atomic_commit
vfunc. When using helpers this callback is the only one which can fail an atomic commit, everything else must complete successfully.cleanup_fb
This hook is called to clean up any resources allocated for the given framebuffer and plane configuration in prepare_fb.
This callback is used by the atomic modeset helpers and by the transitional plane helpers, but it is optional.
atomic_check
Drivers should check plane specific constraints in this hook.
When using
drm_atomic_helper_check_planes()
plane’s atomic_check hooks are called before the ones for CRTCs, which allows drivers to request shared resources that the CRTC controls here. For more complicated dependencies the driver can call the provided check helpers multiple times until the computed state has a final configuration and everything has been checked.This function is also allowed to inspect any other object’s state and can add more state objects to the atomic commit if needed. Care must be taken though to ensure that state check and compute functions for these added states are all called, and derived state in other objects all updated. Again the recommendation is to just call check helpers until a maximal configuration is reached.
This callback is used by the atomic modeset helpers and by the transitional plane helpers, but it is optional.
NOTE:
This function is called in the check phase of an atomic update. The driver is not allowed to change anything outside of the free-standing state objects passed-in or assembled in the overall
drm_atomic_state
update tracking structure.RETURNS:
0 on success, -EINVAL if the state or the transition can’t be supported, -ENOMEM on memory allocation failure and -EDEADLK if an attempt to obtain another state object ran into a
drm_modeset_lock
deadlock.atomic_update
Drivers should use this function to update the plane state. This hook is called in-between the
drm_crtc_helper_funcs.atomic_begin
and drm_crtc_helper_funcs.atomic_flush callbacks.Note that the power state of the display pipe when this function is called depends upon the exact helpers and calling sequence the driver has picked. See
drm_atomic_helper_commit_planes()
for a discussion of the tradeoffs and variants of plane commit helpers.This callback is used by the atomic modeset helpers and by the transitional plane helpers, but it is optional.
atomic_disable
Drivers should use this function to unconditionally disable a plane. This hook is called in-between the
drm_crtc_helper_funcs.atomic_begin
and drm_crtc_helper_funcs.atomic_flush callbacks. It is an alternative to atomic_update, which will be called for disabling planes, too, if the atomic_disable hook isn’t implemented.This hook is also useful to disable planes in preparation of a modeset, by calling
drm_atomic_helper_disable_planes_on_crtc()
from thedrm_crtc_helper_funcs.disable
hook.Note that the power state of the display pipe when this function is called depends upon the exact helpers and calling sequence the driver has picked. See
drm_atomic_helper_commit_planes()
for a discussion of the tradeoffs and variants of plane commit helpers.This callback is used by the atomic modeset helpers and by the transitional plane helpers, but it is optional.
atomic_async_check
Drivers should set this function pointer to check if the plane state can be updated in a async fashion. Here async means “not vblank synchronized”.
This hook is called by drm_atomic_async_check() to establish if a given update can be committed asynchronously, that is, if it can jump ahead of the state currently queued for update.
RETURNS:
Return 0 on success and any error returned indicates that the update can not be applied in asynchronous manner.
atomic_async_update
Drivers should set this function pointer to perform asynchronous updates of planes, that is, jump ahead of the currently queued state and update the plane. Here async means “not vblank synchronized”.
This hook is called by
drm_atomic_helper_async_commit()
.An async update will happen on legacy cursor updates. An async update won’t happen if there is an outstanding commit modifying the same plane.
Note that unlike
drm_plane_helper_funcs.atomic_update
this hook takes the newdrm_plane_state
as parameter. When doing async_update drivers shouldn’t replace thedrm_plane_state
but update the current one with the new plane configurations in the new plane_state.Drivers should also swap the framebuffers between current plane state (
drm_plane.state
) and new_state. This is required since cleanup for async commits is performed on the new state, rather than old state like for traditional commits. Since we want to give up the reference on the current (old) fb instead of our brand new one, swap them in the driver during the async commit.- FIXME:
- It only works for single plane updates
- Async Pageflips are not supported yet
- Some hw might still scan out the old buffer until the next vblank, however we let go of the fb references as soon as we run this hook. For now drivers must implement their own workers for deferring if needed, until a common solution is created.
Description
These functions are used by the atomic helpers and by the transitional plane helpers.
-
void
drm_plane_helper_add
(struct drm_plane *plane, const struct drm_plane_helper_funcs *funcs)¶ sets the helper vtable for a plane
Parameters
struct drm_plane *plane
- DRM plane
const struct drm_plane_helper_funcs *funcs
- helper vtable to set for plane
-
struct
drm_mode_config_helper_funcs
¶ global modeset helper operations
Definition
struct drm_mode_config_helper_funcs {
void (*atomic_commit_tail)(struct drm_atomic_state *state);
};
Members
atomic_commit_tail
This hook is used by the default atomic_commit() hook implemented in
drm_atomic_helper_commit()
together with the nonblocking commit helpers (seedrm_atomic_helper_setup_commit()
for a starting point) to implement blocking and nonblocking commits easily. It is not used by the atomic helpersThis function is called when the new atomic state has already been swapped into the various state pointers. The passed in state therefore contains copies of the old/previous state. This hook should commit the new state into hardware. Note that the helpers have already waited for preceeding atomic commits and fences, but drivers can add more waiting calls at the start of their implementation, e.g. to wait for driver-internal request for implicit syncing, before starting to commit the update to the hardware.
After the atomic update is committed to the hardware this hook needs to call
drm_atomic_helper_commit_hw_done()
. Then wait for the upate to be executed by the hardware, for example usingdrm_atomic_helper_wait_for_vblanks()
ordrm_atomic_helper_wait_for_flip_done()
, and then clean up the old framebuffers usingdrm_atomic_helper_cleanup_planes()
.When disabling a CRTC this hook _must_ stall for the commit to complete. Vblank waits don’t work on disabled CRTC, hence the core can’t take care of this. And it also can’t rely on the vblank event, since that can be signalled already when the screen shows black, which can happen much earlier than the last hardware access needed to shut off the display pipeline completely.
This hook is optional, the default implementation is
drm_atomic_helper_commit_tail()
.
Description
These helper functions are used by the atomic helpers.
Atomic Modeset Helper Functions Reference¶
Overview¶
This helper library provides implementations of check and commit functions on top of the CRTC modeset helper callbacks and the plane helper callbacks. It also provides convenience implementations for the atomic state handling callbacks for drivers which don’t need to subclass the drm core structures to add their own additional internal state.
This library also provides default implementations for the check callback in
drm_atomic_helper_check()
and for the commit callback with
drm_atomic_helper_commit()
. But the individual stages and callbacks are
exposed to allow drivers to mix and match and e.g. use the plane helpers only
together with a driver private modeset implementation.
This library also provides implementations for all the legacy driver
interfaces on top of the atomic interface. See drm_atomic_helper_set_config()
,
drm_atomic_helper_disable_plane()
, drm_atomic_helper_disable_plane()
and the
various functions to implement set_property callbacks. New drivers must not
implement these functions themselves but must use the provided helpers.
The atomic helper uses the same function table structures as all other
modesetting helpers. See the documentation for struct drm_crtc_helper_funcs
,
struct drm_encoder_helper_funcs
and struct drm_connector_helper_funcs
. It
also shares the struct drm_plane_helper_funcs
function table with the plane
helpers.
Implementing Asynchronous Atomic Commit¶
Nonblocking atomic commits should use struct drm_crtc_commit
to sequence
different operations against each another. Locks, especially struct
drm_modeset_lock
, should not be held in worker threads or any other
asynchronous context used to commit the hardware state.
drm_atomic_helper_commit()
implements the recommended sequence for
nonblocking commits, using drm_atomic_helper_setup_commit()
internally:
1. Run drm_atomic_helper_prepare_planes()
. Since this can fail and we
need to propagate out of memory/VRAM errors to userspace, it must be called
synchronously.
2. Synchronize with any outstanding nonblocking commit worker threads which
might be affected by the new state update. This is handled by
drm_atomic_helper_setup_commit()
.
Asynchronous workers need to have sufficient parallelism to be able to run
different atomic commits on different CRTCs in parallel. The simplest way to
achieve this is by running them on the system_unbound_wq
work queue. Note
that drivers are not required to split up atomic commits and run an
individual commit in parallel - userspace is supposed to do that if it cares.
But it might be beneficial to do that for modesets, since those necessarily
must be done as one global operation, and enabling or disabling a CRTC can
take a long time. But even that is not required.
IMPORTANT: A drm_atomic_state
update for multiple CRTCs is sequenced
against all CRTCs therein. Therefore for atomic state updates which only flip
planes the driver must not get the struct drm_crtc_state
of unrelated CRTCs
in its atomic check code: This would prevent committing of atomic updates to
multiple CRTCs in parallel. In general, adding additional state structures
should be avoided as much as possible, because this reduces parallelism in
(nonblocking) commits, both due to locking and due to commit sequencing
requirements.
3. The software state is updated synchronously with
drm_atomic_helper_swap_state()
. Doing this under the protection of all modeset
locks means concurrent callers never see inconsistent state. Note that commit
workers do not hold any locks; their access is only coordinated through
ordering. If workers would access state only through the pointers in the
free-standing state objects (currently not the case for any driver) then even
multiple pending commits could be in-flight at the same time.
4. Schedule a work item to do all subsequent steps, using the split-out
commit helpers: a) pre-plane commit b) plane commit c) post-plane commit and
then cleaning up the framebuffers after the old framebuffer is no longer
being displayed. The scheduled work should synchronize against other workers
using the drm_crtc_commit
infrastructure as needed. See
drm_atomic_helper_setup_commit()
for more details.
Helper Functions Reference¶
-
drm_atomic_crtc_for_each_plane
(plane, crtc)¶ iterate over planes currently attached to CRTC
Parameters
plane
- the loop cursor
crtc
- the CRTC whose planes are iterated
Description
This iterates over the current state, useful (for example) when applying
atomic state after it has been checked and swapped. To iterate over the
planes which will be attached (more useful in code called from
drm_mode_config_funcs.atomic_check
) see
drm_atomic_crtc_state_for_each_plane()
.
-
drm_atomic_crtc_state_for_each_plane
(plane, crtc_state)¶ iterate over attached planes in new state
Parameters
plane
- the loop cursor
crtc_state
- the incoming CRTC state
Description
Similar to drm_crtc_for_each_plane(), but iterates the planes that will be
attached if the specified state is applied. Useful during for example
in code called from drm_mode_config_funcs.atomic_check
operations, to
validate the incoming state.
-
drm_atomic_crtc_state_for_each_plane_state
(plane, plane_state, crtc_state)¶ iterate over attached planes in new state
Parameters
plane
- the loop cursor
plane_state
- loop cursor for the plane’s state, must be const
crtc_state
- the incoming CRTC state
Description
Similar to drm_crtc_for_each_plane(), but iterates the planes that will be
attached if the specified state is applied. Useful during for example
in code called from drm_mode_config_funcs.atomic_check
operations, to
validate the incoming state.
Compared to just drm_atomic_crtc_state_for_each_plane()
this also fills in a
const plane_state. This is useful when a driver just wants to peek at other
active planes on this CRTC, but does not need to change it.
-
bool
drm_atomic_plane_disabling
(struct drm_plane_state *old_plane_state, struct drm_plane_state *new_plane_state)¶ check whether a plane is being disabled
Parameters
struct drm_plane_state *old_plane_state
- old atomic plane state
struct drm_plane_state *new_plane_state
- new atomic plane state
Description
Checks the atomic state of a plane to determine whether it’s being disabled or not. This also WARNs if it detects an invalid state (both CRTC and FB need to either both be NULL or both be non-NULL).
Return
True if the plane is being disabled, false otherwise.
-
int
drm_atomic_helper_check_modeset
(struct drm_device *dev, struct drm_atomic_state *state)¶ validate state object for modeset changes
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *state
- the driver state object
Description
Check the state object to see if the requested state is physically possible. This does all the CRTC and connector related computations for an atomic update and adds any additional connectors needed for full modesets. It calls the various per-object callbacks in the follow order:
drm_connector_helper_funcs.atomic_best_encoder
for determining the new encoder.drm_connector_helper_funcs.atomic_check
to validate the connector state.- If it’s determined a modeset is needed then all connectors on the affected
CRTC are added and
drm_connector_helper_funcs.atomic_check
is run on them. drm_encoder_helper_funcs.mode_valid
,drm_bridge_funcs.mode_valid
anddrm_crtc_helper_funcs.mode_valid
are called on the affected components.drm_bridge_funcs.mode_fixup
is called on all encoder bridges.drm_encoder_helper_funcs.atomic_check
is called to validate any encoder state. This function is only called when the encoder will be part of a configured CRTC, it must not be used for implementing connector property validation. If this function is NULL,drm_atomic_encoder_helper_funcs.mode_fixup
is called instead.drm_crtc_helper_funcs.mode_fixup
is called last, to fix up the mode with CRTC constraints.
drm_crtc_state.mode_changed
is set when the input mode is changed.
drm_crtc_state.connectors_changed
is set when a connector is added or
removed from the CRTC. drm_crtc_state.active_changed
is set when
drm_crtc_state.active
changes, which is used for DPMS.
drm_crtc_state.no_vblank
is set from the result of drm_dev_has_vblank()
.
See also: drm_atomic_crtc_needs_modeset()
IMPORTANT:
Drivers which set drm_crtc_state.mode_changed
(e.g. in their
drm_plane_helper_funcs.atomic_check
hooks if a plane update can’t be done
without a full modeset) _must_ call this function afterwards after that
change. It is permitted to call this function multiple times for the same
update, e.g. when the drm_crtc_helper_funcs.atomic_check
functions depend
upon the adjusted dotclock for fifo space allocation and watermark
computation.
Return
Zero for success or -errno
-
int
drm_atomic_helper_check_plane_state
(struct drm_plane_state *plane_state, const struct drm_crtc_state *crtc_state, int min_scale, int max_scale, bool can_position, bool can_update_disabled)¶ Check plane state for validity
Parameters
struct drm_plane_state *plane_state
- plane state to check
const struct drm_crtc_state *crtc_state
- CRTC state to check
int min_scale
- minimum src:dest scaling factor in 16.16 fixed point
int max_scale
- maximum src:dest scaling factor in 16.16 fixed point
bool can_position
- is it legal to position the plane such that it doesn’t cover the entire CRTC? This will generally only be false for primary planes.
bool can_update_disabled
- can the plane be updated while the CRTC is disabled?
Description
Checks that a desired plane update is valid, and updates various bits of derived state (clipped coordinates etc.). Drivers that provide their own plane handling rather than helper-provided implementations may still wish to call this function to avoid duplication of error checking code.
Return
Zero if update appears valid, error code on failure
-
int
drm_atomic_helper_check_planes
(struct drm_device *dev, struct drm_atomic_state *state)¶ validate state object for planes changes
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *state
- the driver state object
Description
Check the state object to see if the requested state is physically possible.
This does all the plane update related checks using by calling into the
drm_crtc_helper_funcs.atomic_check
and drm_plane_helper_funcs.atomic_check
hooks provided by the driver.
It also sets drm_crtc_state.planes_changed
to indicate that a CRTC has
updated planes.
Return
Zero for success or -errno
-
int
drm_atomic_helper_check
(struct drm_device *dev, struct drm_atomic_state *state)¶ validate state object
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *state
- the driver state object
Description
Check the state object to see if the requested state is physically possible.
Only CRTCs and planes have check callbacks, so for any additional (global)
checking that a driver needs it can simply wrap that around this function.
Drivers without such needs can directly use this as their
drm_mode_config_funcs.atomic_check
callback.
This just wraps the two parts of the state checking for planes and modeset
state in the default order: First it calls drm_atomic_helper_check_modeset()
and then drm_atomic_helper_check_planes()
. The assumption is that the
drm_plane_helper_funcs.atomic_check and drm_crtc_helper_funcs.atomic_check
functions depend upon an updated adjusted_mode.clock to e.g. properly compute
watermarks.
Note that zpos normalization will add all enable planes to the state which might not desired for some drivers. For example enable/disable of a cursor plane which have fixed zpos value would trigger all other enabled planes to be forced to the state change.
Return
Zero for success or -errno
-
void
drm_atomic_helper_update_legacy_modeset_state
(struct drm_device *dev, struct drm_atomic_state *old_state)¶ update legacy modeset state
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *old_state
- atomic state object with old state structures
Description
This function updates all the various legacy modeset state pointers in connectors, encoders and CRTCs.
Drivers can use this for building their own atomic commit if they don’t have a pure helper-based modeset implementation.
Since these updates are not synchronized with lockings, only code paths
called from drm_mode_config_helper_funcs.atomic_commit_tail
can look at the
legacy state filled out by this helper. Defacto this means this helper and
the legacy state pointers are only really useful for transitioning an
existing driver to the atomic world.
-
void
drm_atomic_helper_calc_timestamping_constants
(struct drm_atomic_state *state)¶ update vblank timestamping constants
Parameters
struct drm_atomic_state *state
- atomic state object
Description
Updates the timestamping constants used for precise vblank timestamps
by calling drm_calc_timestamping_constants()
for all enabled crtcs in state.
-
void
drm_atomic_helper_commit_modeset_disables
(struct drm_device *dev, struct drm_atomic_state *old_state)¶ modeset commit to disable outputs
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *old_state
- atomic state object with old state structures
Description
This function shuts down all the outputs that need to be shut down and prepares them (if required) with the new mode.
For compatibility with legacy CRTC helpers this should be called before
drm_atomic_helper_commit_planes()
, which is what the default commit function
does. But drivers with different needs can group the modeset commits together
and do the plane commits at the end. This is useful for drivers doing runtime
PM since planes updates then only happen when the CRTC is actually enabled.
-
void
drm_atomic_helper_commit_modeset_enables
(struct drm_device *dev, struct drm_atomic_state *old_state)¶ modeset commit to enable outputs
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *old_state
- atomic state object with old state structures
Description
This function enables all the outputs with the new configuration which had to be turned off for the update.
For compatibility with legacy CRTC helpers this should be called after
drm_atomic_helper_commit_planes()
, which is what the default commit function
does. But drivers with different needs can group the modeset commits together
and do the plane commits at the end. This is useful for drivers doing runtime
PM since planes updates then only happen when the CRTC is actually enabled.
-
int
drm_atomic_helper_wait_for_fences
(struct drm_device *dev, struct drm_atomic_state *state, bool pre_swap)¶ wait for fences stashed in plane state
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *state
- atomic state object with old state structures
bool pre_swap
- If true, do an interruptible wait, and state is the new state. Otherwise state is the old state.
Description
For implicit sync, driver should fish the exclusive fence out from the
incoming fb’s and stash it in the drm_plane_state. This is called after
drm_atomic_helper_swap_state()
so it uses the current plane state (and
just uses the atomic state to find the changed planes)
Note that pre_swap is needed since the point where we block for fences moves
around depending upon whether an atomic commit is blocking or
non-blocking. For non-blocking commit all waiting needs to happen after
drm_atomic_helper_swap_state()
is called, but for blocking commits we want
to wait before we do anything that can’t be easily rolled back. That is
before we call drm_atomic_helper_swap_state()
.
Returns zero if success or < 0 if dma_fence_wait()
fails.
-
void
drm_atomic_helper_wait_for_vblanks
(struct drm_device *dev, struct drm_atomic_state *old_state)¶ wait for vblank on CRTCs
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *old_state
- atomic state object with old state structures
Description
Helper to, after atomic commit, wait for vblanks on all affected
CRTCs (ie. before cleaning up old framebuffers using
drm_atomic_helper_cleanup_planes()
). It will only wait on CRTCs where the
framebuffers have actually changed to optimize for the legacy cursor and
plane update use-case.
Drivers using the nonblocking commit tracking support initialized by calling
drm_atomic_helper_setup_commit()
should look at
drm_atomic_helper_wait_for_flip_done()
as an alternative.
-
void
drm_atomic_helper_wait_for_flip_done
(struct drm_device *dev, struct drm_atomic_state *old_state)¶ wait for all page flips to be done
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *old_state
- atomic state object with old state structures
Description
Helper to, after atomic commit, wait for page flips on all affected
crtcs (ie. before cleaning up old framebuffers using
drm_atomic_helper_cleanup_planes()
). Compared to
drm_atomic_helper_wait_for_vblanks()
this waits for the completion on all
CRTCs, assuming that cursors-only updates are signalling their completion
immediately (or using a different path).
This requires that drivers use the nonblocking commit tracking support
initialized using drm_atomic_helper_setup_commit()
.
-
void
drm_atomic_helper_commit_tail
(struct drm_atomic_state *old_state)¶ commit atomic update to hardware
Parameters
struct drm_atomic_state *old_state
- atomic state object with old state structures
Description
This is the default implementation for the
drm_mode_config_helper_funcs.atomic_commit_tail
hook, for drivers
that do not support runtime_pm or do not need the CRTC to be
enabled to perform a commit. Otherwise, see
drm_atomic_helper_commit_tail_rpm()
.
Note that the default ordering of how the various stages are called is to match the legacy modeset helper library closest.
-
void
drm_atomic_helper_commit_tail_rpm
(struct drm_atomic_state *old_state)¶ commit atomic update to hardware
Parameters
struct drm_atomic_state *old_state
- new modeset state to be committed
Description
This is an alternative implementation for the
drm_mode_config_helper_funcs.atomic_commit_tail
hook, for drivers
that support runtime_pm or need the CRTC to be enabled to perform a
commit. Otherwise, one should use the default implementation
drm_atomic_helper_commit_tail()
.
-
int
drm_atomic_helper_async_check
(struct drm_device *dev, struct drm_atomic_state *state)¶ check if state can be commited asynchronously
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *state
- the driver state object
Description
This helper will check if it is possible to commit the state asynchronously. Async commits are not supposed to swap the states like normal sync commits but just do in-place changes on the current state.
It will return 0 if the commit can happen in an asynchronous fashion or error if not. Note that error just mean it can’t be commited asynchronously, if it fails the commit should be treated like a normal synchronous commit.
-
void
drm_atomic_helper_async_commit
(struct drm_device *dev, struct drm_atomic_state *state)¶ commit state asynchronously
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *state
- the driver state object
Description
This function commits a state asynchronously, i.e., not vblank synchronized. It should be used on a state only when drm_atomic_async_check() succeeds. Async commits are not supposed to swap the states like normal sync commits, but just do in-place changes on the current state.
TODO: Implement full swap instead of doing in-place changes.
-
int
drm_atomic_helper_commit
(struct drm_device *dev, struct drm_atomic_state *state, bool nonblock)¶ commit validated state object
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *state
- the driver state object
bool nonblock
- whether nonblocking behavior is requested.
Description
This function commits a with drm_atomic_helper_check()
pre-validated state
object. This can still fail when e.g. the framebuffer reservation fails. This
function implements nonblocking commits, using
drm_atomic_helper_setup_commit()
and related functions.
Committing the actual hardware state is done through the
drm_mode_config_helper_funcs.atomic_commit_tail
callback, or its default
implementation drm_atomic_helper_commit_tail()
.
Return
Zero for success or -errno.
-
int
drm_atomic_helper_setup_commit
(struct drm_atomic_state *state, bool nonblock)¶ setup possibly nonblocking commit
Parameters
struct drm_atomic_state *state
- new modeset state to be committed
bool nonblock
- whether nonblocking behavior is requested.
Description
This function prepares state to be used by the atomic helper’s support for
nonblocking commits. Drivers using the nonblocking commit infrastructure
should always call this function from their
drm_mode_config_funcs.atomic_commit
hook.
To be able to use this support drivers need to use a few more helper
functions. drm_atomic_helper_wait_for_dependencies()
must be called before
actually committing the hardware state, and for nonblocking commits this call
must be placed in the async worker. See also drm_atomic_helper_swap_state()
and its stall parameter, for when a driver’s commit hooks look at the
drm_crtc.state
, drm_plane.state
or drm_connector.state
pointer directly.
Completion of the hardware commit step must be signalled using
drm_atomic_helper_commit_hw_done()
. After this step the driver is not allowed
to read or change any permanent software or hardware modeset state. The only
exception is state protected by other means than drm_modeset_lock
locks.
Only the free standing state with pointers to the old state structures can
be inspected, e.g. to clean up old buffers using
drm_atomic_helper_cleanup_planes()
.
At the very end, before cleaning up state drivers must call
drm_atomic_helper_commit_cleanup_done()
.
This is all implemented by in drm_atomic_helper_commit()
, giving drivers a
complete and easy-to-use default implementation of the atomic_commit() hook.
The tracking of asynchronously executed and still pending commits is done
using the core structure drm_crtc_commit
.
By default there’s no need to clean up resources allocated by this function
explicitly: drm_atomic_state_default_clear()
will take care of that
automatically.
0 on success. -EBUSY when userspace schedules nonblocking commits too fast, -ENOMEM on allocation failures and -EINTR when a signal is pending.
Return
-
void
drm_atomic_helper_wait_for_dependencies
(struct drm_atomic_state *old_state)¶ wait for required preceeding commits
Parameters
struct drm_atomic_state *old_state
- atomic state object with old state structures
Description
This function waits for all preceeding commits that touch the same CRTC as
old_state to both be committed to the hardware (as signalled by
drm_atomic_helper_commit_hw_done()
) and executed by the hardware (as signalled
by calling drm_crtc_send_vblank_event()
on the drm_crtc_state.event
).
This is part of the atomic helper support for nonblocking commits, see
drm_atomic_helper_setup_commit()
for an overview.
-
void
drm_atomic_helper_fake_vblank
(struct drm_atomic_state *old_state)¶ fake VBLANK events if needed
Parameters
struct drm_atomic_state *old_state
- atomic state object with old state structures
Description
This function walks all CRTCs and fakes VBLANK events on those with
drm_crtc_state.no_vblank
set to true and drm_crtc_state.event
!= NULL.
The primary use of this function is writeback connectors working in oneshot
mode and faking VBLANK events. In this case they only fake the VBLANK event
when a job is queued, and any change to the pipeline that does not touch the
connector is leading to timeouts when calling
drm_atomic_helper_wait_for_vblanks()
or
drm_atomic_helper_wait_for_flip_done()
. In addition to writeback
connectors, this function can also fake VBLANK events for CRTCs without
VBLANK interrupt.
This is part of the atomic helper support for nonblocking commits, see
drm_atomic_helper_setup_commit()
for an overview.
-
void
drm_atomic_helper_commit_hw_done
(struct drm_atomic_state *old_state)¶ setup possible nonblocking commit
Parameters
struct drm_atomic_state *old_state
- atomic state object with old state structures
Description
This function is used to signal completion of the hardware commit step. After
this step the driver is not allowed to read or change any permanent software
or hardware modeset state. The only exception is state protected by other
means than drm_modeset_lock
locks.
Drivers should try to postpone any expensive or delayed cleanup work after this function is called.
This is part of the atomic helper support for nonblocking commits, see
drm_atomic_helper_setup_commit()
for an overview.
-
void
drm_atomic_helper_commit_cleanup_done
(struct drm_atomic_state *old_state)¶ signal completion of commit
Parameters
struct drm_atomic_state *old_state
- atomic state object with old state structures
Description
This signals completion of the atomic update old_state, including any
cleanup work. If used, it must be called right before calling
drm_atomic_state_put()
.
This is part of the atomic helper support for nonblocking commits, see
drm_atomic_helper_setup_commit()
for an overview.
-
int
drm_atomic_helper_prepare_planes
(struct drm_device *dev, struct drm_atomic_state *state)¶ prepare plane resources before commit
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *state
- atomic state object with new state structures
Description
This function prepares plane state, specifically framebuffers, for the new
configuration, by calling drm_plane_helper_funcs.prepare_fb
. If any failure
is encountered this function will call drm_plane_helper_funcs.cleanup_fb
on
any already successfully prepared framebuffer.
Return
0 on success, negative error code on failure.
-
void
drm_atomic_helper_commit_planes
(struct drm_device *dev, struct drm_atomic_state *old_state, uint32_t flags)¶ commit plane state
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *old_state
- atomic state object with old state structures
uint32_t flags
- flags for committing plane state
Description
This function commits the new plane state using the plane and atomic helper functions for planes and CRTCs. It assumes that the atomic state has already been pushed into the relevant object state pointers, since this step can no longer fail.
It still requires the global state object old_state to know which planes and crtcs need to be updated though.
Note that this function does all plane updates across all CRTCs in one step.
If the hardware can’t support this approach look at
drm_atomic_helper_commit_planes_on_crtc()
instead.
Plane parameters can be updated by applications while the associated CRTC is disabled. The DRM/KMS core will store the parameters in the plane state, which will be available to the driver when the CRTC is turned on. As a result most drivers don’t need to be immediately notified of plane updates for a disabled CRTC.
Unless otherwise needed, drivers are advised to set the ACTIVE_ONLY flag in flags in order not to receive plane update notifications related to a disabled CRTC. This avoids the need to manually ignore plane updates in driver code when the driver and/or hardware can’t or just don’t need to deal with updates on disabled CRTCs, for example when supporting runtime PM.
Drivers may set the NO_DISABLE_AFTER_MODESET flag in flags if the relevant
display controllers require to disable a CRTC’s planes when the CRTC is
disabled. This function would skip the drm_plane_helper_funcs.atomic_disable
call for a plane if the CRTC of the old plane state needs a modesetting
operation. Of course, the drivers need to disable the planes in their CRTC
disable callbacks since no one else would do that.
The drm_atomic_helper_commit()
default implementation doesn’t set the
ACTIVE_ONLY flag to most closely match the behaviour of the legacy helpers.
This should not be copied blindly by drivers.
-
void
drm_atomic_helper_commit_planes_on_crtc
(struct drm_crtc_state *old_crtc_state)¶ commit plane state for a CRTC
Parameters
struct drm_crtc_state *old_crtc_state
- atomic state object with the old CRTC state
Description
This function commits the new plane state using the plane and atomic helper functions for planes on the specific CRTC. It assumes that the atomic state has already been pushed into the relevant object state pointers, since this step can no longer fail.
This function is useful when plane updates should be done CRTC-by-CRTC
instead of one global step like drm_atomic_helper_commit_planes()
does.
This function can only be savely used when planes are not allowed to move between different CRTCs because this function doesn’t handle inter-CRTC depencies. Callers need to ensure that either no such depencies exist, resolve them through ordering of commit calls or through some other means.
-
void
drm_atomic_helper_disable_planes_on_crtc
(struct drm_crtc_state *old_crtc_state, bool atomic)¶ helper to disable CRTC’s planes
Parameters
struct drm_crtc_state *old_crtc_state
- atomic state object with the old CRTC state
bool atomic
- if set, synchronize with CRTC’s atomic_begin/flush hooks
Description
Disables all planes associated with the given CRTC. This can be used for instance in the CRTC helper atomic_disable callback to disable all planes.
If the atomic-parameter is set the function calls the CRTC’s atomic_begin hook before and atomic_flush hook after disabling the planes.
It is a bug to call this function without having implemented the
drm_plane_helper_funcs.atomic_disable
plane hook.
-
void
drm_atomic_helper_cleanup_planes
(struct drm_device *dev, struct drm_atomic_state *old_state)¶ cleanup plane resources after commit
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *old_state
- atomic state object with old state structures
Description
This function cleans up plane state, specifically framebuffers, from the old configuration. Hence the old configuration must be perserved in old_state to be able to call this function.
This function must also be called on the new state when the atomic update
fails at any point after calling drm_atomic_helper_prepare_planes()
.
-
int
drm_atomic_helper_swap_state
(struct drm_atomic_state *state, bool stall)¶ store atomic state into current sw state
Parameters
struct drm_atomic_state *state
- atomic state
bool stall
- stall for preceeding commits
Description
This function stores the atomic state into the current state pointers in all driver objects. It should be called after all failing steps have been done and succeeded, but before the actual hardware state is committed.
For cleanup and error recovery the current state for all changed objects will be swapped into state.
With that sequence it fits perfectly into the plane prepare/cleanup sequence:
- Call
drm_atomic_helper_prepare_planes()
with the staged atomic state. - Do any other steps that might fail.
- Put the staged state into the current state pointers with this function.
- Actually commit the hardware state.
5. Call drm_atomic_helper_cleanup_planes()
with state, which since step 3
contains the old state. Also do any other cleanup required with that state.
stall must be set when nonblocking commits for this driver directly access
the drm_plane.state
, drm_crtc.state
or drm_connector.state
pointer. With
the current atomic helpers this is almost always the case, since the helpers
don’t pass the right state structures to the callbacks.
Returns 0 on success. Can return -ERESTARTSYS when stall is true and the waiting for the previous commits has been interrupted.
Return
-
int
drm_atomic_helper_update_plane
(struct drm_plane *plane, struct drm_crtc *crtc, struct drm_framebuffer *fb, int crtc_x, int crtc_y, unsigned int crtc_w, unsigned int crtc_h, uint32_t src_x, uint32_t src_y, uint32_t src_w, uint32_t src_h, struct drm_modeset_acquire_ctx *ctx)¶ Helper for primary plane update using atomic
Parameters
struct drm_plane *plane
- plane object to update
struct drm_crtc *crtc
- owning CRTC of owning plane
struct drm_framebuffer *fb
- framebuffer to flip onto plane
int crtc_x
- x offset of primary plane on crtc
int crtc_y
- y offset of primary plane on crtc
unsigned int crtc_w
- width of primary plane rectangle on crtc
unsigned int crtc_h
- height of primary plane rectangle on crtc
uint32_t src_x
- x offset of fb for panning
uint32_t src_y
- y offset of fb for panning
uint32_t src_w
- width of source rectangle in fb
uint32_t src_h
- height of source rectangle in fb
struct drm_modeset_acquire_ctx *ctx
- lock acquire context
Description
Provides a default plane update handler using the atomic driver interface.
Return
Zero on success, error code on failure
-
int
drm_atomic_helper_disable_plane
(struct drm_plane *plane, struct drm_modeset_acquire_ctx *ctx)¶ Helper for primary plane disable using * atomic
Parameters
struct drm_plane *plane
- plane to disable
struct drm_modeset_acquire_ctx *ctx
- lock acquire context
Description
Provides a default plane disable handler using the atomic driver interface.
Return
Zero on success, error code on failure
-
int
drm_atomic_helper_set_config
(struct drm_mode_set *set, struct drm_modeset_acquire_ctx *ctx)¶ set a new config from userspace
Parameters
struct drm_mode_set *set
- mode set configuration
struct drm_modeset_acquire_ctx *ctx
- lock acquisition context
Description
Provides a default CRTC set_config handler using the atomic driver interface.
NOTE
For backwards compatibility with old userspace this automatically
resets the “link-status” property to GOOD, to force any link
re-training. The SETCRTC ioctl does not define whether an update does
need a full modeset or just a plane update, hence we’re allowed to do
that. See also drm_connector_set_link_status_property()
.
Return
Returns 0 on success, negative errno numbers on failure.
-
int
drm_atomic_helper_disable_all
(struct drm_device *dev, struct drm_modeset_acquire_ctx *ctx)¶ disable all currently active outputs
Parameters
struct drm_device *dev
- DRM device
struct drm_modeset_acquire_ctx *ctx
- lock acquisition context
Description
Loops through all connectors, finding those that aren’t turned off and then turns them off by setting their DPMS mode to OFF and deactivating the CRTC that they are connected to.
This is used for example in suspend/resume to disable all currently active
functions when suspending. If you just want to shut down everything at e.g.
driver unload, look at drm_atomic_helper_shutdown()
.
Note that if callers haven’t already acquired all modeset locks this might
return -EDEADLK, which must be handled by calling drm_modeset_backoff()
.
See also:
drm_atomic_helper_suspend()
, drm_atomic_helper_resume()
and
drm_atomic_helper_shutdown()
.
Return
0 on success or a negative error code on failure.
-
void
drm_atomic_helper_shutdown
(struct drm_device *dev)¶ shutdown all CRTC
Parameters
struct drm_device *dev
- DRM device
Description
This shuts down all CRTC, which is useful for driver unloading. Shutdown on
suspend should instead be handled with drm_atomic_helper_suspend()
, since
that also takes a snapshot of the modeset state to be restored on resume.
This is just a convenience wrapper around drm_atomic_helper_disable_all()
,
and it is the atomic version of drm_crtc_force_disable_all().
-
struct drm_atomic_state *
drm_atomic_helper_duplicate_state
(struct drm_device *dev, struct drm_modeset_acquire_ctx *ctx)¶ duplicate an atomic state object
Parameters
struct drm_device *dev
- DRM device
struct drm_modeset_acquire_ctx *ctx
- lock acquisition context
Description
Makes a copy of the current atomic state by looping over all objects and duplicating their respective states. This is used for example by suspend/ resume support code to save the state prior to suspend such that it can be restored upon resume.
Note that this treats atomic state as persistent between save and restore. Drivers must make sure that this is possible and won’t result in confusion or erroneous behaviour.
Note that if callers haven’t already acquired all modeset locks this might
return -EDEADLK, which must be handled by calling drm_modeset_backoff()
.
See also:
drm_atomic_helper_suspend()
, drm_atomic_helper_resume()
Return
A pointer to the copy of the atomic state object on success or an ERR_PTR()-encoded error code on failure.
-
struct drm_atomic_state *
drm_atomic_helper_suspend
(struct drm_device *dev)¶ subsystem-level suspend helper
Parameters
struct drm_device *dev
- DRM device
Description
Duplicates the current atomic state, disables all active outputs and then
returns a pointer to the original atomic state to the caller. Drivers can
pass this pointer to the drm_atomic_helper_resume()
helper upon resume to
restore the output configuration that was active at the time the system
entered suspend.
Note that it is potentially unsafe to use this. The atomic state object returned by this function is assumed to be persistent. Drivers must ensure that this holds true. Before calling this function, drivers must make sure to suspend fbdev emulation so that nothing can be using the device.
See also:
drm_atomic_helper_duplicate_state()
, drm_atomic_helper_disable_all()
,
drm_atomic_helper_resume()
, drm_atomic_helper_commit_duplicated_state()
Return
A pointer to a copy of the state before suspend on success or an ERR_PTR()-
encoded error code on failure. Drivers should store the returned atomic
state object and pass it to the drm_atomic_helper_resume()
helper upon
resume.
-
int
drm_atomic_helper_commit_duplicated_state
(struct drm_atomic_state *state, struct drm_modeset_acquire_ctx *ctx)¶ commit duplicated state
Parameters
struct drm_atomic_state *state
- duplicated atomic state to commit
struct drm_modeset_acquire_ctx *ctx
- pointer to acquire_ctx to use for commit.
Description
The state returned by drm_atomic_helper_duplicate_state()
and
drm_atomic_helper_suspend()
is partially invalid, and needs to
be fixed up before commit.
See also:
drm_atomic_helper_suspend()
Return
0 on success or a negative error code on failure.
-
int
drm_atomic_helper_resume
(struct drm_device *dev, struct drm_atomic_state *state)¶ subsystem-level resume helper
Parameters
struct drm_device *dev
- DRM device
struct drm_atomic_state *state
- atomic state to resume to
Description
Calls drm_mode_config_reset()
to synchronize hardware and software states,
grabs all modeset locks and commits the atomic state object. This can be
used in conjunction with the drm_atomic_helper_suspend()
helper to
implement suspend/resume for drivers that support atomic mode-setting.
See also:
drm_atomic_helper_suspend()
Return
0 on success or a negative error code on failure.
-
int
drm_atomic_helper_page_flip
(struct drm_crtc *crtc, struct drm_framebuffer *fb, struct drm_pending_vblank_event *event, uint32_t flags, struct drm_modeset_acquire_ctx *ctx)¶ execute a legacy page flip
Parameters
struct drm_crtc *crtc
- DRM CRTC
struct drm_framebuffer *fb
- DRM framebuffer
struct drm_pending_vblank_event *event
- optional DRM event to signal upon completion
uint32_t flags
- flip flags for non-vblank sync’ed updates
struct drm_modeset_acquire_ctx *ctx
- lock acquisition context
Description
Provides a default drm_crtc_funcs.page_flip
implementation
using the atomic driver interface.
See also:
drm_atomic_helper_page_flip_target()
Return
Returns 0 on success, negative errno numbers on failure.
-
int
drm_atomic_helper_page_flip_target
(struct drm_crtc *crtc, struct drm_framebuffer *fb, struct drm_pending_vblank_event *event, uint32_t flags, uint32_t target, struct drm_modeset_acquire_ctx *ctx)¶ do page flip on target vblank period.
Parameters
struct drm_crtc *crtc
- DRM CRTC
struct drm_framebuffer *fb
- DRM framebuffer
struct drm_pending_vblank_event *event
- optional DRM event to signal upon completion
uint32_t flags
- flip flags for non-vblank sync’ed updates
uint32_t target
- specifying the target vblank period when the flip to take effect
struct drm_modeset_acquire_ctx *ctx
- lock acquisition context
Description
Provides a default drm_crtc_funcs.page_flip_target
implementation.
Similar to drm_atomic_helper_page_flip()
with extra parameter to specify
target vblank period to flip.
Return
Returns 0 on success, negative errno numbers on failure.
-
int
drm_atomic_helper_legacy_gamma_set
(struct drm_crtc *crtc, u16 *red, u16 *green, u16 *blue, uint32_t size, struct drm_modeset_acquire_ctx *ctx)¶ set the legacy gamma correction table
Parameters
struct drm_crtc *crtc
- CRTC object
u16 *red
- red correction table
u16 *green
- green correction table
u16 *blue
- green correction table
uint32_t size
- size of the tables
struct drm_modeset_acquire_ctx *ctx
- lock acquire context
Description
Implements support for legacy gamma correction table for drivers
that support color management through the DEGAMMA_LUT/GAMMA_LUT
properties. See drm_crtc_enable_color_mgmt()
and the containing chapter for
how the atomic color management and gamma tables work.
-
u32 *
drm_atomic_helper_bridge_propagate_bus_fmt
(struct drm_bridge *bridge, struct drm_bridge_state *bridge_state, struct drm_crtc_state *crtc_state, struct drm_connector_state *conn_state, u32 output_fmt, unsigned int *num_input_fmts)¶ Propagate output format to the input end of a bridge
Parameters
struct drm_bridge *bridge
- bridge control structure
struct drm_bridge_state *bridge_state
- new bridge state
struct drm_crtc_state *crtc_state
- new CRTC state
struct drm_connector_state *conn_state
- new connector state
u32 output_fmt
- tested output bus format
unsigned int *num_input_fmts
- will contain the size of the returned array
Description
This helper is a pluggable implementation of the
drm_bridge_funcs.atomic_get_input_bus_fmts
operation for bridges that don’t
modify the bus configuration between their input and their output. It
returns an array of input formats with a single element set to output_fmt.
Return
a valid format array of size num_input_fmts, or NULL if the allocation failed
Atomic State Reset and Initialization¶
Both the drm core and the atomic helpers assume that there is always the full and correct atomic software state for all connectors, CRTCs and planes available. Which is a bit a problem on driver load and also after system suspend. One way to solve this is to have a hardware state read-out infrastructure which reconstructs the full software state (e.g. the i915 driver).
The simpler solution is to just reset the software state to everything off,
which is easiest to do by calling drm_mode_config_reset()
. To facilitate this
the atomic helpers provide default reset implementations for all hooks.
On the upside the precise state tracking of atomic simplifies system suspend
and resume a lot. For drivers using drm_mode_config_reset()
a complete recipe
is implemented in drm_atomic_helper_suspend()
and drm_atomic_helper_resume()
.
For other drivers the building blocks are split out, see the documentation
for these functions.
Atomic State Helper Reference¶
-
void
__drm_atomic_helper_crtc_state_reset
(struct drm_crtc_state *crtc_state, struct drm_crtc *crtc)¶ reset the CRTC state
Parameters
struct drm_crtc_state *crtc_state
- atomic CRTC state, must not be NULL
struct drm_crtc *crtc
- CRTC object, must not be NULL
Description
Initializes the newly allocated crtc_state with default values. This is useful for drivers that subclass the CRTC state.
-
void
__drm_atomic_helper_crtc_reset
(struct drm_crtc *crtc, struct drm_crtc_state *crtc_state)¶ reset state on CRTC
Parameters
struct drm_crtc *crtc
- drm CRTC
struct drm_crtc_state *crtc_state
- CRTC state to assign
Description
Initializes the newly allocated crtc_state and assigns it to
the drm_crtc->state
pointer of crtc, usually required when
initializing the drivers or when called from the drm_crtc_funcs.reset
hook.
This is useful for drivers that subclass the CRTC state.
-
void
drm_atomic_helper_crtc_reset
(struct drm_crtc *crtc)¶ default
drm_crtc_funcs.reset
hook for CRTCs
Parameters
struct drm_crtc *crtc
- drm CRTC
Description
Resets the atomic state for crtc by freeing the state pointer (which might be NULL, e.g. at driver load time) and allocating a new empty state object.
-
void
__drm_atomic_helper_crtc_duplicate_state
(struct drm_crtc *crtc, struct drm_crtc_state *state)¶ copy atomic CRTC state
Parameters
struct drm_crtc *crtc
- CRTC object
struct drm_crtc_state *state
- atomic CRTC state
Description
Copies atomic state from a CRTC’s current state and resets inferred values. This is useful for drivers that subclass the CRTC state.
-
struct drm_crtc_state *
drm_atomic_helper_crtc_duplicate_state
(struct drm_crtc *crtc)¶ default state duplicate hook
Parameters
struct drm_crtc *crtc
- drm CRTC
Description
Default CRTC state duplicate hook for drivers which don’t have their own subclassed CRTC state structure.
-
void
__drm_atomic_helper_crtc_destroy_state
(struct drm_crtc_state *state)¶ release CRTC state
Parameters
struct drm_crtc_state *state
- CRTC state object to release
Description
Releases all resources stored in the CRTC state without actually freeing the memory of the CRTC state. This is useful for drivers that subclass the CRTC state.
-
void
drm_atomic_helper_crtc_destroy_state
(struct drm_crtc *crtc, struct drm_crtc_state *state)¶ default state destroy hook
Parameters
struct drm_crtc *crtc
- drm CRTC
struct drm_crtc_state *state
- CRTC state object to release
Description
Default CRTC state destroy hook for drivers which don’t have their own subclassed CRTC state structure.
-
void
__drm_atomic_helper_plane_state_reset
(struct drm_plane_state *plane_state, struct drm_plane *plane)¶ resets plane state to default values
Parameters
struct drm_plane_state *plane_state
- atomic plane state, must not be NULL
struct drm_plane *plane
- plane object, must not be NULL
Description
Initializes the newly allocated plane_state with default values. This is useful for drivers that subclass the CRTC state.
-
void
__drm_atomic_helper_plane_reset
(struct drm_plane *plane, struct drm_plane_state *plane_state)¶ reset state on plane
Parameters
struct drm_plane *plane
- drm plane
struct drm_plane_state *plane_state
- plane state to assign
Description
Initializes the newly allocated plane_state and assigns it to
the drm_crtc->state
pointer of plane, usually required when
initializing the drivers or when called from the drm_plane_funcs.reset
hook.
This is useful for drivers that subclass the plane state.
-
void
drm_atomic_helper_plane_reset
(struct drm_plane *plane)¶ default
drm_plane_funcs.reset
hook for planes
Parameters
struct drm_plane *plane
- drm plane
Description
Resets the atomic state for plane by freeing the state pointer (which might be NULL, e.g. at driver load time) and allocating a new empty state object.
-
void
__drm_atomic_helper_plane_duplicate_state
(struct drm_plane *plane, struct drm_plane_state *state)¶ copy atomic plane state
Parameters
struct drm_plane *plane
- plane object
struct drm_plane_state *state
- atomic plane state
Description
Copies atomic state from a plane’s current state. This is useful for drivers that subclass the plane state.
-
struct drm_plane_state *
drm_atomic_helper_plane_duplicate_state
(struct drm_plane *plane)¶ default state duplicate hook
Parameters
struct drm_plane *plane
- drm plane
Description
Default plane state duplicate hook for drivers which don’t have their own subclassed plane state structure.
-
void
__drm_atomic_helper_plane_destroy_state
(struct drm_plane_state *state)¶ release plane state
Parameters
struct drm_plane_state *state
- plane state object to release
Description
Releases all resources stored in the plane state without actually freeing the memory of the plane state. This is useful for drivers that subclass the plane state.
-
void
drm_atomic_helper_plane_destroy_state
(struct drm_plane *plane, struct drm_plane_state *state)¶ default state destroy hook
Parameters
struct drm_plane *plane
- drm plane
struct drm_plane_state *state
- plane state object to release
Description
Default plane state destroy hook for drivers which don’t have their own subclassed plane state structure.
-
void
__drm_atomic_helper_connector_state_reset
(struct drm_connector_state *conn_state, struct drm_connector *connector)¶ reset the connector state
Parameters
struct drm_connector_state *conn_state
- atomic connector state, must not be NULL
struct drm_connector *connector
- connectotr object, must not be NULL
Description
Initializes the newly allocated conn_state with default values. This is useful for drivers that subclass the connector state.
-
void
__drm_atomic_helper_connector_reset
(struct drm_connector *connector, struct drm_connector_state *conn_state)¶ reset state on connector
Parameters
struct drm_connector *connector
- drm connector
struct drm_connector_state *conn_state
- connector state to assign
Description
Initializes the newly allocated conn_state and assigns it to
the drm_connector->state
pointer of connector, usually required when
initializing the drivers or when called from the drm_connector_funcs.reset
hook.
This is useful for drivers that subclass the connector state.
-
void
drm_atomic_helper_connector_reset
(struct drm_connector *connector)¶ default
drm_connector_funcs.reset
hook for connectors
Parameters
struct drm_connector *connector
- drm connector
Description
Resets the atomic state for connector by freeing the state pointer (which might be NULL, e.g. at driver load time) and allocating a new empty state object.
-
void
drm_atomic_helper_connector_tv_reset
(struct drm_connector *connector)¶ Resets TV connector properties
Parameters
struct drm_connector *connector
- DRM connector
Description
Resets the TV-related properties attached to a connector.
-
void
__drm_atomic_helper_connector_duplicate_state
(struct drm_connector *connector, struct drm_connector_state *state)¶ copy atomic connector state
Parameters
struct drm_connector *connector
- connector object
struct drm_connector_state *state
- atomic connector state
Description
Copies atomic state from a connector’s current state. This is useful for drivers that subclass the connector state.
-
struct drm_connector_state *
drm_atomic_helper_connector_duplicate_state
(struct drm_connector *connector)¶ default state duplicate hook
Parameters
struct drm_connector *connector
- drm connector
Description
Default connector state duplicate hook for drivers which don’t have their own subclassed connector state structure.
-
void
__drm_atomic_helper_connector_destroy_state
(struct drm_connector_state *state)¶ release connector state
Parameters
struct drm_connector_state *state
- connector state object to release
Description
Releases all resources stored in the connector state without actually freeing the memory of the connector state. This is useful for drivers that subclass the connector state.
-
void
drm_atomic_helper_connector_destroy_state
(struct drm_connector *connector, struct drm_connector_state *state)¶ default state destroy hook
Parameters
struct drm_connector *connector
- drm connector
struct drm_connector_state *state
- connector state object to release
Description
Default connector state destroy hook for drivers which don’t have their own subclassed connector state structure.
-
void
__drm_atomic_helper_private_obj_duplicate_state
(struct drm_private_obj *obj, struct drm_private_state *state)¶ copy atomic private state
Parameters
struct drm_private_obj *obj
- CRTC object
struct drm_private_state *state
- new private object state
Description
Copies atomic state from a private objects’s current state and resets inferred values. This is useful for drivers that subclass the private state.
-
void
__drm_atomic_helper_bridge_duplicate_state
(struct drm_bridge *bridge, struct drm_bridge_state *state)¶ Copy atomic bridge state
Parameters
struct drm_bridge *bridge
- bridge object
struct drm_bridge_state *state
- atomic bridge state
Description
Copies atomic state from a bridge’s current state and resets inferred values. This is useful for drivers that subclass the bridge state.
-
struct drm_bridge_state *
drm_atomic_helper_bridge_duplicate_state
(struct drm_bridge *bridge)¶ Duplicate a bridge state object
Parameters
struct drm_bridge *bridge
- bridge object
Description
Allocates a new bridge state and initializes it with the current bridge
state values. This helper is meant to be used as a bridge
drm_bridge_funcs.atomic_duplicate_state
hook for bridges that don’t
subclass the bridge state.
-
void
drm_atomic_helper_bridge_destroy_state
(struct drm_bridge *bridge, struct drm_bridge_state *state)¶ Destroy a bridge state object
Parameters
struct drm_bridge *bridge
- the bridge this state refers to
struct drm_bridge_state *state
- bridge state to destroy
Description
Destroys a bridge state previously created by
drm_atomic_helper_bridge_reset`() or
:c:type:`drm_atomic_helper_bridge_duplicate_state`(). This helper is meant to be
used as a bridge :c:type:`drm_bridge_funcs.atomic_destroy_state
hook for bridges
that don’t subclass the bridge state.
-
void
__drm_atomic_helper_bridge_reset
(struct drm_bridge *bridge, struct drm_bridge_state *state)¶ Initialize a bridge state to its default
Parameters
struct drm_bridge *bridge
- the bridge this state refers to
struct drm_bridge_state *state
- bridge state to initialize
Description
Initializes the bridge state to default values. This is meant to be called
by the bridge drm_bridge_funcs.atomic_reset
hook for bridges that subclass
the bridge state.
-
struct drm_bridge_state *
drm_atomic_helper_bridge_reset
(struct drm_bridge *bridge)¶ Allocate and initialize a bridge state to its default
Parameters
struct drm_bridge *bridge
- the bridge this state refers to
Description
Allocates the bridge state and initializes it to default values. This helper
is meant to be used as a bridge drm_bridge_funcs.atomic_reset
hook for
bridges that don’t subclass the bridge state.
Simple KMS Helper Reference¶
This helper library provides helpers for drivers for simple display hardware.
drm_simple_display_pipe_init()
initializes a simple display pipeline
which has only one full-screen scanout buffer feeding one output. The
pipeline is represented by struct drm_simple_display_pipe
and binds
together drm_plane
, drm_crtc
and drm_encoder
structures into one fixed
entity. Some flexibility for code reuse is provided through a separately
allocated drm_connector
object and supporting optional drm_bridge
encoder drivers.
Many drivers require only a very simple encoder that fulfills the minimum
requirements of the display pipeline and does not add additional
functionality. The function drm_simple_encoder_init()
provides an
implementation of such an encoder.
-
struct
drm_simple_display_pipe_funcs
¶ helper operations for a simple display pipeline
Definition
struct drm_simple_display_pipe_funcs {
enum drm_mode_status (*mode_valid)(struct drm_simple_display_pipe *pipe, const struct drm_display_mode *mode);
void (*enable)(struct drm_simple_display_pipe *pipe,struct drm_crtc_state *crtc_state, struct drm_plane_state *plane_state);
void (*disable)(struct drm_simple_display_pipe *pipe);
int (*check)(struct drm_simple_display_pipe *pipe,struct drm_plane_state *plane_state, struct drm_crtc_state *crtc_state);
void (*update)(struct drm_simple_display_pipe *pipe, struct drm_plane_state *old_plane_state);
int (*prepare_fb)(struct drm_simple_display_pipe *pipe, struct drm_plane_state *plane_state);
void (*cleanup_fb)(struct drm_simple_display_pipe *pipe, struct drm_plane_state *plane_state);
int (*enable_vblank)(struct drm_simple_display_pipe *pipe);
void (*disable_vblank)(struct drm_simple_display_pipe *pipe);
};
Members
mode_valid
This callback is used to check if a specific mode is valid in the crtc used in this simple display pipe. This should be implemented if the display pipe has some sort of restriction in the modes it can display. For example, a given display pipe may be responsible to set a clock value. If the clock can not produce all the values for the available modes then this callback can be used to restrict the number of modes to only the ones that can be displayed. Another reason can be bandwidth mitigation: the memory port on the display controller can have bandwidth limitations not allowing pixel data to be fetched at any rate.
This hook is used by the probe helpers to filter the mode list in
drm_helper_probe_single_connector_modes()
, and it is used by the atomic helpers to validate modes supplied by userspace indrm_atomic_helper_check_modeset()
.This function is optional.
NOTE:
Since this function is both called from the check phase of an atomic commit, and the mode validation in the probe paths it is not allowed to look at anything else but the passed-in mode, and validate it against configuration-invariant hardware constraints.
RETURNS:
drm_mode_status Enum
enable
- This function should be used to enable the pipeline. It is called when the underlying crtc is enabled. This hook is optional.
disable
- This function should be used to disable the pipeline. It is called when the underlying crtc is disabled. This hook is optional.
check
This function is called in the check phase of an atomic update, specifically when the underlying plane is checked. The simple display pipeline helpers already check that the plane is not scaled, fills the entire visible area and is always enabled when the crtc is also enabled. This hook is optional.
RETURNS:
0 on success, -EINVAL if the state or the transition can’t be supported, -ENOMEM on memory allocation failure and -EDEADLK if an attempt to obtain another state object ran into a
drm_modeset_lock
deadlock.update
This function is called when the underlying plane state is updated. This hook is optional.
This is the function drivers should submit the
drm_pending_vblank_event
from. Using eitherdrm_crtc_arm_vblank_event()
, when the driver supports vblank interrupt handling, ordrm_crtc_send_vblank_event()
for more complex case. In case the hardware lacks vblank support entirely, drivers can setstruct drm_crtc_state
.no_vblank instruct drm_simple_display_pipe_funcs
.check and let DRM’s atomic helper fake a vblank event.prepare_fb
Optional, called by
drm_plane_helper_funcs.prepare_fb
. Please read the documentation for thedrm_plane_helper_funcs.prepare_fb
hook for more details.Drivers which always have their buffers pinned should use
drm_gem_fb_simple_display_pipe_prepare_fb()
for this hook.cleanup_fb
- Optional, called by
drm_plane_helper_funcs.cleanup_fb
. Please read the documentation for thedrm_plane_helper_funcs.cleanup_fb
hook for more details. enable_vblank
- Optional, called by
drm_crtc_funcs.enable_vblank
. Please read the documentation for thedrm_crtc_funcs.enable_vblank
hook for more details. disable_vblank
- Optional, called by
drm_crtc_funcs.disable_vblank
. Please read the documentation for thedrm_crtc_funcs.disable_vblank
hook for more details.
-
struct
drm_simple_display_pipe
¶ simple display pipeline
Definition
struct drm_simple_display_pipe {
struct drm_crtc crtc;
struct drm_plane plane;
struct drm_encoder encoder;
struct drm_connector *connector;
const struct drm_simple_display_pipe_funcs *funcs;
};
Members
crtc
- CRTC control structure
plane
- Plane control structure
encoder
- Encoder control structure
connector
- Connector control structure
funcs
- Pipeline control functions (optional)
Description
Simple display pipeline with plane, crtc and encoder collapsed into one
entity. It should be initialized by calling drm_simple_display_pipe_init()
.
-
int
drm_simple_encoder_init
(struct drm_device *dev, struct drm_encoder *encoder, int encoder_type)¶ Initialize a preallocated encoder with basic functionality.
Parameters
struct drm_device *dev
- drm device
struct drm_encoder *encoder
- the encoder to initialize
int encoder_type
- user visible type of the encoder
Description
Initialises a preallocated encoder that has no further functionality. Settings for possible CRTC and clones are left to their initial values. The encoder will be cleaned up automatically as part of the mode-setting cleanup.
The caller of drm_simple_encoder_init()
is responsible for freeing
the encoder’s memory after the encoder has been cleaned up. At the
moment this only works reliably if the encoder data structure is
stored in the device structure. Free the encoder’s memory as part of
the device release function.
- FIXME: Later improvements to DRM’s resource management may allow for
- an automated
kfree()
of the encoder’s memory.
Return
Zero on success, error code on failure.
-
int
drm_simple_display_pipe_attach_bridge
(struct drm_simple_display_pipe *pipe, struct drm_bridge *bridge)¶ Attach a bridge to the display pipe
Parameters
struct drm_simple_display_pipe *pipe
- simple display pipe object
struct drm_bridge *bridge
- bridge to attach
Description
Makes it possible to still use the drm_simple_display_pipe helpers when a DRM bridge has to be used.
Note that you probably want to initialize the pipe by passing a NULL
connector to drm_simple_display_pipe_init()
.
Return
Zero on success, negative error code on failure.
-
int
drm_simple_display_pipe_init
(struct drm_device *dev, struct drm_simple_display_pipe *pipe, const struct drm_simple_display_pipe_funcs *funcs, const uint32_t *formats, unsigned int format_count, const uint64_t *format_modifiers, struct drm_connector *connector)¶ Initialize a simple display pipeline
Parameters
struct drm_device *dev
- DRM device
struct drm_simple_display_pipe *pipe
- simple display pipe object to initialize
const struct drm_simple_display_pipe_funcs *funcs
- callbacks for the display pipe (optional)
const uint32_t *formats
- array of supported formats (DRM_FORMAT_*)
unsigned int format_count
- number of elements in formats
const uint64_t *format_modifiers
- array of formats modifiers
struct drm_connector *connector
- connector to attach and register (optional)
Description
Sets up a display pipeline which consist of a really simple plane-crtc-encoder pipe.
If a connector is supplied, the pipe will be coupled with the provided
connector. You may supply a NULL connector when using drm bridges, that
handle connectors themselves (see drm_simple_display_pipe_attach_bridge()
).
Teardown of a simple display pipe is all handled automatically by the drm
core through calling drm_mode_config_cleanup()
. Drivers afterwards need to
release the memory for the structure themselves.
Return
Zero on success, negative error code on failure.
fbdev Helper Functions Reference¶
The fb helper functions are useful to provide an fbdev on top of a drm kernel mode setting driver. They can be used mostly independently from the crtc helper functions used by many drivers to implement the kernel mode setting interfaces.
Drivers that support a dumb buffer with a virtual address and mmap support,
should try out the generic fbdev emulation using drm_fbdev_generic_setup()
.
It will automatically set up deferred I/O if the driver requires a shadow
buffer.
At runtime drivers should restore the fbdev console by using
drm_fb_helper_lastclose()
as their drm_driver.lastclose
callback.
They should also notify the fb helper code from updates to the output
configuration by using drm_fb_helper_output_poll_changed()
as their
drm_mode_config_funcs.output_poll_changed
callback.
For suspend/resume consider using drm_mode_config_helper_suspend()
and
drm_mode_config_helper_resume()
which takes care of fbdev as well.
All other functions exported by the fb helper library can be used to implement the fbdev driver interface by the driver.
It is possible, though perhaps somewhat tricky, to implement race-free
hotplug detection using the fbdev helpers. The drm_fb_helper_prepare()
helper must be called first to initialize the minimum required to make
hotplug detection work. Drivers also need to make sure to properly set up
the drm_mode_config.funcs
member. After calling drm_kms_helper_poll_init()
it is safe to enable interrupts and start processing hotplug events. At the
same time, drivers should initialize all modeset objects such as CRTCs,
encoders and connectors. To finish up the fbdev helper initialization, the
drm_fb_helper_init()
function is called. To probe for all attached displays
and set up an initial configuration using the detected hardware, drivers
should call drm_fb_helper_initial_config()
.
If drm_framebuffer_funcs.dirty
is set, the
drm_fb_helper_{cfb,sys}_{write,fillrect,copyarea,imageblit} functions will
accumulate changes and schedule drm_fb_helper.dirty_work
to run right
away. This worker then calls the dirty() function ensuring that it will
always run in process context since the fb_*() function could be running in
atomic context. If drm_fb_helper_deferred_io()
is used as the deferred_io
callback it will also schedule dirty_work with the damage collected from the
mmap page writes.
Deferred I/O is not compatible with SHMEM. Such drivers should request an
fbdev shadow buffer and call drm_fbdev_generic_setup()
instead.
-
struct
drm_fb_helper_surface_size
¶ describes fbdev size and scanout surface size
Definition
struct drm_fb_helper_surface_size {
u32 fb_width;
u32 fb_height;
u32 surface_width;
u32 surface_height;
u32 surface_bpp;
u32 surface_depth;
};
Members
fb_width
- fbdev width
fb_height
- fbdev height
surface_width
- scanout buffer width
surface_height
- scanout buffer height
surface_bpp
- scanout buffer bpp
surface_depth
- scanout buffer depth
Description
Note that the scanout surface width/height may be larger than the fbdev
width/height. In case of multiple displays, the scanout surface is sized
according to the largest width/height (so it is large enough for all CRTCs
to scanout). But the fbdev width/height is sized to the minimum width/
height of all the displays. This ensures that fbcon fits on the smallest
of the attached displays. fb_width/fb_height is used by
drm_fb_helper_fill_info()
to fill out the fb_info.var
structure.
-
struct
drm_fb_helper_funcs
¶ driver callbacks for the fbdev emulation library
Definition
struct drm_fb_helper_funcs {
int (*fb_probe)(struct drm_fb_helper *helper, struct drm_fb_helper_surface_size *sizes);
};
Members
fb_probe
Driver callback to allocate and initialize the fbdev info structure. Furthermore it also needs to allocate the DRM framebuffer used to back the fbdev.
This callback is mandatory.
RETURNS:
The driver should return 0 on success and a negative error code on failure.
Description
Driver callbacks used by the fbdev emulation helper library.
-
struct
drm_fb_helper
¶ main structure to emulate fbdev on top of KMS
Definition
struct drm_fb_helper {
struct drm_client_dev client;
struct drm_client_buffer *buffer;
struct drm_framebuffer *fb;
struct drm_device *dev;
const struct drm_fb_helper_funcs *funcs;
struct fb_info *fbdev;
u32 pseudo_palette[17];
struct drm_clip_rect damage_clip;
spinlock_t damage_lock;
struct work_struct damage_work;
struct work_struct resume_work;
struct mutex lock;
struct list_head kernel_fb_list;
bool delayed_hotplug;
bool deferred_setup;
int preferred_bpp;
};
Members
client
- DRM client used by the generic fbdev emulation.
buffer
- Framebuffer used by the generic fbdev emulation.
fb
- Scanout framebuffer object
dev
- DRM device
funcs
- driver callbacks for fb helper
fbdev
- emulated fbdev device info struct
pseudo_palette
- fake palette of 16 colors
damage_clip
- clip rectangle used with deferred_io to accumulate damage to the screen buffer
damage_lock
- spinlock protecting damage_clip
damage_work
- worker used to flush the framebuffer
resume_work
- worker used during resume if the console lock is already taken
lock
Top-level FBDEV helper lock. This protects all internal data structures and lists, such as connector_info and crtc_info.
FIXME: fbdev emulation locking is a mess and long term we want to protect all helper internal state with this lock as well as reduce core KMS locking as much as possible.
kernel_fb_list
- Entry on the global kernel_fb_helper_list, used for kgdb entry/exit.
delayed_hotplug
- A hotplug was received while fbdev wasn’t in control of the DRM device, i.e. another KMS master was active. The output configuration needs to be reprobe when fbdev is in control again.
deferred_setup
If no outputs are connected (disconnected or unknown) the FB helper code will defer setup until at least one of the outputs shows up. This field keeps track of the status so that setup can be retried at every hotplug event until it succeeds eventually.
Protected by lock.
preferred_bpp
Temporary storage for the driver’s preferred BPP setting passed to FB helper initialization. This needs to be tracked so that deferred FB helper setup can pass this on.
See also: deferred_setup
Description
This is the main structure used by the fbdev helpers. Drivers supporting
fbdev emulation should embedded this into their overall driver structure.
Drivers must also fill out a struct drm_fb_helper_funcs
with a few
operations.
-
DRM_FB_HELPER_DEFAULT_OPS
()¶ helper define for drm drivers
Parameters
Description
Helper define to register default implementations of drm_fb_helper functions. To be used in struct fb_ops of drm drivers.
-
int
drm_fb_helper_remove_conflicting_framebuffers
(struct apertures_struct *a, const char *name, bool primary)¶ remove firmware-configured framebuffers
Parameters
struct apertures_struct *a
- memory range, users of which are to be removed
const char *name
- requesting driver name
bool primary
- also kick vga16fb if present
Description
This function removes framebuffer devices (initialized by firmware/bootloader) which use memory range described by a. If a is NULL all such devices are removed.
-
int
drm_fb_helper_remove_conflicting_pci_framebuffers
(struct pci_dev *pdev, const char *name)¶ remove firmware-configured framebuffers for PCI devices
Parameters
struct pci_dev *pdev
- PCI device
const char *name
- requesting driver name
Description
This function removes framebuffer devices (eg. initialized by firmware) using memory range configured for any of pdev’s memory bars.
The function assumes that PCI device with shadowed ROM drives a primary display and so kicks out vga16fb.
-
int
drm_fb_helper_debug_enter
(struct fb_info *info)¶ implementation for
fb_ops.fb_debug_enter
Parameters
struct fb_info *info
- fbdev registered by the helper
-
int
drm_fb_helper_debug_leave
(struct fb_info *info)¶ implementation for
fb_ops.fb_debug_leave
Parameters
struct fb_info *info
- fbdev registered by the helper
-
int
drm_fb_helper_restore_fbdev_mode_unlocked
(struct drm_fb_helper *fb_helper)¶ restore fbdev configuration
Parameters
struct drm_fb_helper *fb_helper
- driver-allocated fbdev helper, can be NULL
Description
This should be called from driver’s drm drm_driver.lastclose
callback
when implementing an fbcon on top of kms using this helper. This ensures that
the user isn’t greeted with a black screen when e.g. X dies.
Return
Zero if everything went ok, negative error code otherwise.
-
int
drm_fb_helper_blank
(int blank, struct fb_info *info)¶ implementation for
fb_ops.fb_blank
Parameters
int blank
- desired blanking state
struct fb_info *info
- fbdev registered by the helper
-
void
drm_fb_helper_prepare
(struct drm_device *dev, struct drm_fb_helper *helper, const struct drm_fb_helper_funcs *funcs)¶ setup a drm_fb_helper structure
Parameters
struct drm_device *dev
- DRM device
struct drm_fb_helper *helper
- driver-allocated fbdev helper structure to set up
const struct drm_fb_helper_funcs *funcs
- pointer to structure of functions associate with this helper
Description
Sets up the bare minimum to make the framebuffer helper usable. This is useful to implement race-free initialization of the polling helpers.
-
int
drm_fb_helper_init
(struct drm_device *dev, struct drm_fb_helper *fb_helper)¶ initialize a
struct drm_fb_helper
Parameters
struct drm_device *dev
- drm device
struct drm_fb_helper *fb_helper
- driver-allocated fbdev helper structure to initialize
Description
This allocates the structures for the fbdev helper with the given limits.
Note that this won’t yet touch the hardware (through the driver interfaces)
nor register the fbdev. This is only done in drm_fb_helper_initial_config()
to allow driver writes more control over the exact init sequence.
Drivers must call drm_fb_helper_prepare()
before calling this function.
Return
Zero if everything went ok, nonzero otherwise.
-
struct fb_info *
drm_fb_helper_alloc_fbi
(struct drm_fb_helper *fb_helper)¶ allocate fb_info and some of its members
Parameters
struct drm_fb_helper *fb_helper
- driver-allocated fbdev helper
Description
A helper to alloc fb_info and the members cmap and apertures. Called
by the driver within the fb_probe fb_helper callback function. Drivers do not
need to release the allocated fb_info structure themselves, this is
automatically done when calling drm_fb_helper_fini()
.
Return
fb_info pointer if things went okay, pointer containing error code otherwise
-
void
drm_fb_helper_unregister_fbi
(struct drm_fb_helper *fb_helper)¶ unregister fb_info framebuffer device
Parameters
struct drm_fb_helper *fb_helper
- driver-allocated fbdev helper, can be NULL
Description
A wrapper around unregister_framebuffer, to release the fb_info
framebuffer device. This must be called before releasing all resources for
fb_helper by calling drm_fb_helper_fini()
.
-
void
drm_fb_helper_fini
(struct drm_fb_helper *fb_helper)¶ finialize a
struct drm_fb_helper
Parameters
struct drm_fb_helper *fb_helper
- driver-allocated fbdev helper, can be NULL
Description
This cleans up all remaining resources associated with fb_helper.
-
void
drm_fb_helper_deferred_io
(struct fb_info *info, struct list_head *pagelist)¶ fbdev deferred_io callback function
Parameters
struct fb_info *info
- fb_info struct pointer
struct list_head *pagelist
- list of mmap framebuffer pages that have to be flushed
Description
This function is used as the fb_deferred_io.deferred_io
callback function for flushing the fbdev mmap writes.
-
ssize_t
drm_fb_helper_sys_read
(struct fb_info *info, char __user *buf, size_t count, loff_t *ppos)¶ wrapper around fb_sys_read
Parameters
struct fb_info *info
- fb_info struct pointer
char __user *buf
- userspace buffer to read from framebuffer memory
size_t count
- number of bytes to read from framebuffer memory
loff_t *ppos
- read offset within framebuffer memory
Description
A wrapper around fb_sys_read implemented by fbdev core
-
ssize_t
drm_fb_helper_sys_write
(struct fb_info *info, const char __user *buf, size_t count, loff_t *ppos)¶ wrapper around fb_sys_write
Parameters
struct fb_info *info
- fb_info struct pointer
const char __user *buf
- userspace buffer to write to framebuffer memory
size_t count
- number of bytes to write to framebuffer memory
loff_t *ppos
- write offset within framebuffer memory
Description
A wrapper around fb_sys_write implemented by fbdev core
-
void
drm_fb_helper_sys_fillrect
(struct fb_info *info, const struct fb_fillrect *rect)¶ wrapper around sys_fillrect
Parameters
struct fb_info *info
- fbdev registered by the helper
const struct fb_fillrect *rect
- info about rectangle to fill
Description
A wrapper around sys_fillrect implemented by fbdev core
-
void
drm_fb_helper_sys_copyarea
(struct fb_info *info, const struct fb_copyarea *area)¶ wrapper around sys_copyarea
Parameters
struct fb_info *info
- fbdev registered by the helper
const struct fb_copyarea *area
- info about area to copy
Description
A wrapper around sys_copyarea implemented by fbdev core
-
void
drm_fb_helper_sys_imageblit
(struct fb_info *info, const struct fb_image *image)¶ wrapper around sys_imageblit
Parameters
struct fb_info *info
- fbdev registered by the helper
const struct fb_image *image
- info about image to blit
Description
A wrapper around sys_imageblit implemented by fbdev core
-
void
drm_fb_helper_cfb_fillrect
(struct fb_info *info, const struct fb_fillrect *rect)¶ wrapper around cfb_fillrect
Parameters
struct fb_info *info
- fbdev registered by the helper
const struct fb_fillrect *rect
- info about rectangle to fill
Description
A wrapper around cfb_fillrect implemented by fbdev core
-
void
drm_fb_helper_cfb_copyarea
(struct fb_info *info, const struct fb_copyarea *area)¶ wrapper around cfb_copyarea
Parameters
struct fb_info *info
- fbdev registered by the helper
const struct fb_copyarea *area
- info about area to copy
Description
A wrapper around cfb_copyarea implemented by fbdev core
-
void
drm_fb_helper_cfb_imageblit
(struct fb_info *info, const struct fb_image *image)¶ wrapper around cfb_imageblit
Parameters
struct fb_info *info
- fbdev registered by the helper
const struct fb_image *image
- info about image to blit
Description
A wrapper around cfb_imageblit implemented by fbdev core
-
void
drm_fb_helper_set_suspend
(struct drm_fb_helper *fb_helper, bool suspend)¶ wrapper around fb_set_suspend
Parameters
struct drm_fb_helper *fb_helper
- driver-allocated fbdev helper, can be NULL
bool suspend
- whether to suspend or resume
Description
A wrapper around fb_set_suspend implemented by fbdev core.
Use drm_fb_helper_set_suspend_unlocked()
if you don’t need to take
the lock yourself
-
void
drm_fb_helper_set_suspend_unlocked
(struct drm_fb_helper *fb_helper, bool suspend)¶ wrapper around fb_set_suspend that also takes the console lock
Parameters
struct drm_fb_helper *fb_helper
- driver-allocated fbdev helper, can be NULL
bool suspend
- whether to suspend or resume
Description
A wrapper around fb_set_suspend()
that takes the console lock. If the lock
isn’t available on resume, a worker is tasked with waiting for the lock
to become available. The console lock can be pretty contented on resume
due to all the printk activity.
This function can be called multiple times with the same state since
fb_info.state
is checked to see if fbdev is running or not before locking.
Use drm_fb_helper_set_suspend()
if you need to take the lock yourself.
-
int
drm_fb_helper_setcmap
(struct fb_cmap *cmap, struct fb_info *info)¶ implementation for
fb_ops.fb_setcmap
Parameters
struct fb_cmap *cmap
- cmap to set
struct fb_info *info
- fbdev registered by the helper
-
int
drm_fb_helper_ioctl
(struct fb_info *info, unsigned int cmd, unsigned long arg)¶ legacy ioctl implementation
Parameters
struct fb_info *info
- fbdev registered by the helper
unsigned int cmd
- ioctl command
unsigned long arg
- ioctl argument
Description
A helper to implement the standard fbdev ioctl. Only FBIO_WAITFORVSYNC is implemented for now.
-
int
drm_fb_helper_check_var
(struct fb_var_screeninfo *var, struct fb_info *info)¶ implementation for
fb_ops.fb_check_var
Parameters
struct fb_var_screeninfo *var
- screeninfo to check
struct fb_info *info
- fbdev registered by the helper
-
int
drm_fb_helper_set_par
(struct fb_info *info)¶ implementation for
fb_ops.fb_set_par
Parameters
struct fb_info *info
- fbdev registered by the helper
Description
This will let fbcon do the mode init and is called at initialization time by the fbdev core when registering the driver, and later on through the hotplug callback.
-
int
drm_fb_helper_pan_display
(struct fb_var_screeninfo *var, struct fb_info *info)¶ implementation for
fb_ops.fb_pan_display
Parameters
struct fb_var_screeninfo *var
- updated screen information
struct fb_info *info
- fbdev registered by the helper
-
void
drm_fb_helper_fill_info
(struct fb_info *info, struct drm_fb_helper *fb_helper, struct drm_fb_helper_surface_size *sizes)¶ initializes fbdev information
Parameters
struct fb_info *info
- fbdev instance to set up
struct drm_fb_helper *fb_helper
- fb helper instance to use as template
struct drm_fb_helper_surface_size *sizes
- describes fbdev size and scanout surface size
Description
Sets up the variable and fixed fbdev metainformation from the given fb helper
instance and the drm framebuffer allocated in drm_fb_helper.fb
.
Drivers should call this (or their equivalent setup code) from their
drm_fb_helper_funcs.fb_probe
callback after having allocated the fbdev
backing storage framebuffer.
-
int
drm_fb_helper_initial_config
(struct drm_fb_helper *fb_helper, int bpp_sel)¶ setup a sane initial connector configuration
Parameters
struct drm_fb_helper *fb_helper
- fb_helper device struct
int bpp_sel
- bpp value to use for the framebuffer configuration
Description
Scans the CRTCs and connectors and tries to put together an initial setup. At the moment, this is a cloned configuration across all heads with a new framebuffer object as the backing store.
Note that this also registers the fbdev and so allows userspace to call into the driver through the fbdev interfaces.
This function will call down into the drm_fb_helper_funcs.fb_probe
callback
to let the driver allocate and initialize the fbdev info structure and the
drm framebuffer used to back the fbdev. drm_fb_helper_fill_info()
is provided
as a helper to setup simple default values for the fbdev info structure.
HANG DEBUGGING:
When you have fbcon support built-in or already loaded, this function will do
a full modeset to setup the fbdev console. Due to locking misdesign in the
VT/fbdev subsystem that entire modeset sequence has to be done while holding
console_lock. Until console_unlock is called no dmesg lines will be sent out
to consoles, not even serial console. This means when your driver crashes,
you will see absolutely nothing else but a system stuck in this function,
with no further output. Any kind of printk()
you place within your own driver
or in the drm core modeset code will also never show up.
Standard debug practice is to run the fbcon setup without taking the console_lock as a hack, to be able to see backtraces and crashes on the serial line. This can be done by setting the fb.lockless_register_fb=1 kernel cmdline option.
The other option is to just disable fbdev emulation since very likely the first modeset from userspace will crash in the same way, and is even easier to debug. This can be done by setting the drm_kms_helper.fbdev_emulation=0 kernel cmdline option.
Return
Zero if everything went ok, nonzero otherwise.
-
int
drm_fb_helper_hotplug_event
(struct drm_fb_helper *fb_helper)¶ respond to a hotplug notification by probing all the outputs attached to the fb
Parameters
struct drm_fb_helper *fb_helper
- driver-allocated fbdev helper, can be NULL
Description
Scan the connectors attached to the fb_helper and try to put together a setup after notification of a change in output configuration.
Called at runtime, takes the mode config locks to be able to check/change the modeset configuration. Must be run from process context (which usually means either the output polling work or a work item launched from the driver’s hotplug interrupt).
Note that drivers may call this even before calling drm_fb_helper_initial_config but only after drm_fb_helper_init. This allows for a race-free fbcon setup and will make sure that the fbdev emulation will not miss any hotplug events.
Return
0 on success and a non-zero error code otherwise.
-
void
drm_fb_helper_lastclose
(struct drm_device *dev)¶ DRM driver lastclose helper for fbdev emulation
Parameters
struct drm_device *dev
- DRM device
Description
This function can be used as the drm_driver->lastclose
callback for drivers
that only need to call drm_fb_helper_restore_fbdev_mode_unlocked()
.
-
void
drm_fb_helper_output_poll_changed
(struct drm_device *dev)¶ DRM mode config .output_poll_changed helper for fbdev emulation
Parameters
struct drm_device *dev
- DRM device
Description
This function can be used as the
drm_mode_config_funcs.output_poll_changed
callback for drivers that only
need to call drm_fb_helper_hotplug_event()
.
-
void
drm_fbdev_generic_setup
(struct drm_device *dev, unsigned int preferred_bpp)¶ Setup generic fbdev emulation
Parameters
struct drm_device *dev
- DRM device
unsigned int preferred_bpp
- Preferred bits per pixel for the device. dev->mode_config.preferred_depth is used if this is zero.
Description
This function sets up generic fbdev emulation for drivers that supports
dumb buffers with a virtual address and that can be mmap’ed.
drm_fbdev_generic_setup()
shall be called after the DRM driver registered
the new DRM device with drm_dev_register()
.
Restore, hotplug events and teardown are all taken care of. Drivers that do
suspend/resume need to call drm_fb_helper_set_suspend_unlocked()
themselves.
Simple drivers might use drm_mode_config_helper_suspend()
.
Drivers that set the dirty callback on their framebuffer will get a shadow
fbdev buffer that is blitted onto the real buffer. This is done in order to
make deferred I/O work with all kinds of buffers. A shadow buffer can be
requested explicitly by setting struct drm_mode_config
.prefer_shadow or
struct drm_mode_config
.prefer_shadow_fbdev to true beforehand. This is
required to use generic fbdev emulation with SHMEM helpers.
This function is safe to call even when there are no connectors present. Setup will be retried on the next hotplug event.
The fbdev is destroyed by drm_dev_unregister()
.
format Helper Functions Reference¶
-
void
drm_fb_memcpy
(void *dst, void *vaddr, struct drm_framebuffer *fb, struct drm_rect *clip)¶ Copy clip buffer
Parameters
void *dst
- Destination buffer
void *vaddr
- Source buffer
struct drm_framebuffer *fb
- DRM framebuffer
struct drm_rect *clip
- Clip rectangle area to copy
Description
This function does not apply clipping on dst, i.e. the destination is a small buffer containing the clip rect only.
-
void
drm_fb_memcpy_dstclip
(void __iomem *dst, void *vaddr, struct drm_framebuffer *fb, struct drm_rect *clip)¶ Copy clip buffer
Parameters
void __iomem *dst
- Destination buffer (iomem)
void *vaddr
- Source buffer
struct drm_framebuffer *fb
- DRM framebuffer
struct drm_rect *clip
- Clip rectangle area to copy
Description
This function applies clipping on dst, i.e. the destination is a full (iomem) framebuffer but only the clip rect content is copied over.
-
void
drm_fb_swab
(void *dst, void *src, struct drm_framebuffer *fb, struct drm_rect *clip, bool cached)¶ Swap bytes into clip buffer
Parameters
void *dst
- Destination buffer
void *src
- Source buffer
struct drm_framebuffer *fb
- DRM framebuffer
struct drm_rect *clip
- Clip rectangle area to copy
bool cached
- Source buffer is mapped cached (eg. not write-combined)
Description
If cached is false a temporary buffer is used to cache one pixel line at a time to speed up slow uncached reads.
This function does not apply clipping on dst, i.e. the destination is a small buffer containing the clip rect only.
-
void
drm_fb_xrgb8888_to_rgb565
(void *dst, void *vaddr, struct drm_framebuffer *fb, struct drm_rect *clip, bool swab)¶ Convert XRGB8888 to RGB565 clip buffer
Parameters
void *dst
- RGB565 destination buffer
void *vaddr
- XRGB8888 source buffer
struct drm_framebuffer *fb
- DRM framebuffer
struct drm_rect *clip
- Clip rectangle area to copy
bool swab
- Swap bytes
Description
Drivers can use this function for RGB565 devices that don’t natively support XRGB8888.
This function does not apply clipping on dst, i.e. the destination is a small buffer containing the clip rect only.
-
void
drm_fb_xrgb8888_to_rgb565_dstclip
(void __iomem *dst, unsigned int dst_pitch, void *vaddr, struct drm_framebuffer *fb, struct drm_rect *clip, bool swab)¶ Convert XRGB8888 to RGB565 clip buffer
Parameters
void __iomem *dst
- RGB565 destination buffer (iomem)
unsigned int dst_pitch
- destination buffer pitch
void *vaddr
- XRGB8888 source buffer
struct drm_framebuffer *fb
- DRM framebuffer
struct drm_rect *clip
- Clip rectangle area to copy
bool swab
- Swap bytes
Description
Drivers can use this function for RGB565 devices that don’t natively support XRGB8888.
This function applies clipping on dst, i.e. the destination is a full (iomem) framebuffer but only the clip rect content is copied over.
-
void
drm_fb_xrgb8888_to_rgb888_dstclip
(void __iomem *dst, unsigned int dst_pitch, void *vaddr, struct drm_framebuffer *fb, struct drm_rect *clip)¶ Convert XRGB8888 to RGB888 clip buffer
Parameters
void __iomem *dst
- RGB565 destination buffer (iomem)
unsigned int dst_pitch
- destination buffer pitch
void *vaddr
- XRGB8888 source buffer
struct drm_framebuffer *fb
- DRM framebuffer
struct drm_rect *clip
- Clip rectangle area to copy
Description
Drivers can use this function for RGB888 devices that don’t natively support XRGB8888.
This function applies clipping on dst, i.e. the destination is a full (iomem) framebuffer but only the clip rect content is copied over.
-
void
drm_fb_xrgb8888_to_gray8
(u8 *dst, void *vaddr, struct drm_framebuffer *fb, struct drm_rect *clip)¶ Convert XRGB8888 to grayscale
Parameters
u8 *dst
- 8-bit grayscale destination buffer
void *vaddr
- XRGB8888 source buffer
struct drm_framebuffer *fb
- DRM framebuffer
struct drm_rect *clip
- Clip rectangle area to copy
Description
Drm doesn’t have native monochrome or grayscale support. Such drivers can announce the commonly supported XR24 format to userspace and use this function to convert to the native format.
Monochrome drivers will use the most significant bit, where 1 means foreground color and 0 background color.
ITU BT.601 is used for the RGB -> luma (brightness) conversion.
Framebuffer CMA Helper Functions Reference¶
Provides helper functions for creating a cma (contiguous memory allocator) backed framebuffer.
drm_gem_fb_create()
is used in the drm_mode_config_funcs.fb_create
callback function to create a cma backed framebuffer.
-
struct drm_gem_cma_object *
drm_fb_cma_get_gem_obj
(struct drm_framebuffer *fb, unsigned int plane)¶ Get CMA GEM object for framebuffer
Parameters
struct drm_framebuffer *fb
- The framebuffer
unsigned int plane
- Which plane
Description
Return the CMA GEM object for given framebuffer.
This function will usually be called from the CRTC callback functions.
-
dma_addr_t
drm_fb_cma_get_gem_addr
(struct drm_framebuffer *fb, struct drm_plane_state *state, unsigned int plane)¶ Get physical address for framebuffer, for pixel formats where values are grouped in blocks this will get you the beginning of the block
Parameters
struct drm_framebuffer *fb
- The framebuffer
struct drm_plane_state *state
- Which state of drm plane
unsigned int plane
- Which plane Return the CMA GEM address for given framebuffer.
Description
This function will usually be called from the PLANE callback functions.
Framebuffer GEM Helper Reference¶
This library provides helpers for drivers that don’t subclass
drm_framebuffer
and use drm_gem_object
for their backing storage.
Drivers without additional needs to validate framebuffers can simply use
drm_gem_fb_create()
and everything is wired up automatically. Other drivers
can use all parts independently.
-
struct drm_gem_object *
drm_gem_fb_get_obj
(struct drm_framebuffer *fb, unsigned int plane)¶ Get GEM object backing the framebuffer
Parameters
struct drm_framebuffer *fb
- Framebuffer
unsigned int plane
- Plane index
Description
No additional reference is taken beyond the one that the drm_frambuffer
already holds.
Return
Pointer to drm_gem_object
for the given framebuffer and plane index or NULL
if it does not exist.
-
void
drm_gem_fb_destroy
(struct drm_framebuffer *fb)¶ Free GEM backed framebuffer
Parameters
struct drm_framebuffer *fb
- Framebuffer
Description
Frees a GEM backed framebuffer with its backing buffer(s) and the structure
itself. Drivers can use this as their drm_framebuffer_funcs->destroy
callback.
-
int
drm_gem_fb_create_handle
(struct drm_framebuffer *fb, struct drm_file *file, unsigned int *handle)¶ Create handle for GEM backed framebuffer
Parameters
struct drm_framebuffer *fb
- Framebuffer
struct drm_file *file
- DRM file to register the handle for
unsigned int *handle
- Pointer to return the created handle
Description
This function creates a handle for the GEM object backing the framebuffer.
Drivers can use this as their drm_framebuffer_funcs->create_handle
callback. The GETFB IOCTL calls into this callback.
Return
0 on success or a negative error code on failure.
-
int
drm_gem_fb_init_with_funcs
(struct drm_device *dev, struct drm_framebuffer *fb, struct drm_file *file, const struct drm_mode_fb_cmd2 *mode_cmd, const struct drm_framebuffer_funcs *funcs)¶ Helper function for implementing
drm_mode_config_funcs.fb_create
callback in cases when the driver allocates a subclass ofstruct drm_framebuffer
Parameters
struct drm_device *dev
- DRM device
struct drm_framebuffer *fb
- framebuffer object
struct drm_file *file
- DRM file that holds the GEM handle(s) backing the framebuffer
const struct drm_mode_fb_cmd2 *mode_cmd
- Metadata from the userspace framebuffer creation request
const struct drm_framebuffer_funcs *funcs
- vtable to be used for the new framebuffer object
Description
This function can be used to set drm_framebuffer_funcs
for drivers that need
custom framebuffer callbacks. Use drm_gem_fb_create()
if you don’t need to
change drm_framebuffer_funcs
. The function does buffer size validation.
The buffer size validation is for a general case, though, so users should
pay attention to the checks being appropriate for them or, at least,
non-conflicting.
Return
Zero or a negative error code.
-
struct drm_framebuffer *
drm_gem_fb_create_with_funcs
(struct drm_device *dev, struct drm_file *file, const struct drm_mode_fb_cmd2 *mode_cmd, const struct drm_framebuffer_funcs *funcs)¶ Helper function for the
drm_mode_config_funcs.fb_create
callback
Parameters
struct drm_device *dev
- DRM device
struct drm_file *file
- DRM file that holds the GEM handle(s) backing the framebuffer
const struct drm_mode_fb_cmd2 *mode_cmd
- Metadata from the userspace framebuffer creation request
const struct drm_framebuffer_funcs *funcs
- vtable to be used for the new framebuffer object
Description
This function can be used to set drm_framebuffer_funcs
for drivers that need
custom framebuffer callbacks. Use drm_gem_fb_create()
if you don’t need to
change drm_framebuffer_funcs
. The function does buffer size validation.
Return
Pointer to a drm_framebuffer
on success or an error pointer on failure.
-
struct drm_framebuffer *
drm_gem_fb_create
(struct drm_device *dev, struct drm_file *file, const struct drm_mode_fb_cmd2 *mode_cmd)¶ Helper function for the
drm_mode_config_funcs.fb_create
callback
Parameters
struct drm_device *dev
- DRM device
struct drm_file *file
- DRM file that holds the GEM handle(s) backing the framebuffer
const struct drm_mode_fb_cmd2 *mode_cmd
- Metadata from the userspace framebuffer creation request
Description
This function creates a new framebuffer object described by
drm_mode_fb_cmd2
. This description includes handles for the buffer(s)
backing the framebuffer.
If your hardware has special alignment or pitch requirements these should be
checked before calling this function. The function does buffer size
validation. Use drm_gem_fb_create_with_dirty()
if you need framebuffer
flushing.
Drivers can use this as their drm_mode_config_funcs.fb_create
callback.
The ADDFB2 IOCTL calls into this callback.
Return
Pointer to a drm_framebuffer
on success or an error pointer on failure.
-
struct drm_framebuffer *
drm_gem_fb_create_with_dirty
(struct drm_device *dev, struct drm_file *file, const struct drm_mode_fb_cmd2 *mode_cmd)¶ Helper function for the
drm_mode_config_funcs.fb_create
callback
Parameters
struct drm_device *dev
- DRM device
struct drm_file *file
- DRM file that holds the GEM handle(s) backing the framebuffer
const struct drm_mode_fb_cmd2 *mode_cmd
- Metadata from the userspace framebuffer creation request
Description
This function creates a new framebuffer object described by
drm_mode_fb_cmd2
. This description includes handles for the buffer(s)
backing the framebuffer. drm_atomic_helper_dirtyfb()
is used for the dirty
callback giving framebuffer flushing through the atomic machinery. Use
drm_gem_fb_create()
if you don’t need the dirty callback.
The function does buffer size validation.
Drivers should also call drm_plane_enable_fb_damage_clips()
on all planes
to enable userspace to use damage clips also with the ATOMIC IOCTL.
Drivers can use this as their drm_mode_config_funcs.fb_create
callback.
The ADDFB2 IOCTL calls into this callback.
Return
Pointer to a drm_framebuffer
on success or an error pointer on failure.
-
int
drm_gem_fb_afbc_init
(struct drm_device *dev, const struct drm_mode_fb_cmd2 *mode_cmd, struct drm_afbc_framebuffer *afbc_fb)¶ Helper function for drivers using afbc to fill and validate all the afbc-specific
struct drm_afbc_framebuffer
members
Parameters
struct drm_device *dev
- DRM device
const struct drm_mode_fb_cmd2 *mode_cmd
- Metadata from the userspace framebuffer creation request
struct drm_afbc_framebuffer *afbc_fb
- afbc framebuffer
Description
This function can be used by drivers which support afbc to complete
the preparation of struct drm_afbc_framebuffer
. It must be called after
allocating the said struct and calling drm_gem_fb_init_with_funcs()
.
It is caller’s responsibility to put afbc_fb->base.obj objects in case
the call is unsuccessful.
Return
Zero on success or a negative error value on failure.
-
int
drm_gem_fb_prepare_fb
(struct drm_plane *plane, struct drm_plane_state *state)¶ Prepare a GEM backed framebuffer
Parameters
struct drm_plane *plane
- Plane
struct drm_plane_state *state
- Plane state the fence will be attached to
Description
This function extracts the exclusive fence from drm_gem_object.resv
and
attaches it to plane state for the atomic helper to wait on. This is
necessary to correctly implement implicit synchronization for any buffers
shared as a struct dma_buf
. This function can be used as the
drm_plane_helper_funcs.prepare_fb
callback.
There is no need for drm_plane_helper_funcs.cleanup_fb
hook for simple
gem based framebuffer drivers which have their buffers always pinned in
memory.
See drm_atomic_set_fence_for_plane()
for a discussion of implicit and
explicit fencing in atomic modeset updates.
-
int
drm_gem_fb_simple_display_pipe_prepare_fb
(struct drm_simple_display_pipe *pipe, struct drm_plane_state *plane_state)¶ prepare_fb helper for
drm_simple_display_pipe
Parameters
struct drm_simple_display_pipe *pipe
- Simple display pipe
struct drm_plane_state *plane_state
- Plane state
Description
This function uses drm_gem_fb_prepare_fb()
to extract the exclusive fence
from drm_gem_object.resv
and attaches it to plane state for the atomic
helper to wait on. This is necessary to correctly implement implicit
synchronization for any buffers shared as a struct dma_buf
. Drivers can use
this as their drm_simple_display_pipe_funcs.prepare_fb
callback.
See drm_atomic_set_fence_for_plane()
for a discussion of implicit and
explicit fencing in atomic modeset updates.
Bridges¶
Overview¶
struct drm_bridge
represents a device that hangs on to an encoder. These are
handy when a regular drm_encoder
entity isn’t enough to represent the entire
encoder chain.
A bridge is always attached to a single drm_encoder
at a time, but can be
either connected to it directly, or through a chain of bridges:
[ CRTC ---> ] Encoder ---> Bridge A ---> Bridge B
Here, the output of the encoder feeds to bridge A, and that furthers feeds to bridge B. Bridge chains can be arbitrarily long, and shall be fully linear: Chaining multiple bridges to the output of a bridge, or the same bridge to the output of different bridges, is not supported.
Display drivers are responsible for linking encoders with the first bridge
in the chains. This is done by acquiring the appropriate bridge with
of_drm_find_bridge()
or drm_of_find_panel_or_bridge()
, or creating it for a
panel with drm_panel_bridge_add_typed()
(or the managed version
devm_drm_panel_bridge_add_typed()
). Once acquired, the bridge shall be
attached to the encoder with a call to drm_bridge_attach()
.
Bridges are responsible for linking themselves with the next bridge in the
chain, if any. This is done the same way as for encoders, with the call to
drm_bridge_attach()
occurring in the drm_bridge_funcs.attach
operation.
Once these links are created, the bridges can participate along with encoder
functions to perform mode validation and fixup (through
drm_bridge_chain_mode_valid()
and drm_atomic_bridge_chain_check()
), mode
setting (through drm_bridge_chain_mode_set()
), enable (through
drm_atomic_bridge_chain_pre_enable()
and drm_atomic_bridge_chain_enable()
)
and disable (through drm_atomic_bridge_chain_disable()
and
drm_atomic_bridge_chain_post_disable()
). Those functions call the
corresponding operations provided in drm_bridge_funcs
in sequence for all
bridges in the chain.
For display drivers that use the atomic helpers
drm_atomic_helper_check_modeset()
,
drm_atomic_helper_commit_modeset_enables()
and
drm_atomic_helper_commit_modeset_disables()
(either directly in hand-rolled
commit check and commit tail handlers, or through the higher-level
drm_atomic_helper_check()
and drm_atomic_helper_commit_tail()
or
drm_atomic_helper_commit_tail_rpm()
helpers), this is done transparently and
requires no intervention from the driver. For other drivers, the relevant
DRM bridge chain functions shall be called manually.
Bridges also participate in implementing the drm_connector
at the end of
the bridge chain. Display drivers may use the drm_bridge_connector_init()
helper to create the drm_connector
, or implement it manually on top of the
connector-related operations exposed by the bridge (see the overview
documentation of bridge operations for more details).
drm_bridge
, like drm_panel
, aren’t drm_mode_object
entities like planes,
CRTCs, encoders or connectors and hence are not visible to userspace. They
just provide additional hooks to get the desired output at the end of the
encoder chain.
Bridge Operations¶
Bridge drivers expose operations through the drm_bridge_funcs
structure.
The DRM internals (atomic and CRTC helpers) use the helpers defined in
drm_bridge.c to call bridge operations. Those operations are divided in
three big categories to support different parts of the bridge usage.
The encoder-related operations support control of the bridges in the chain, and are roughly counterparts to the
drm_encoder_helper_funcs
operations. They are used by the legacy CRTC and the atomic modeset helpers to perform mode validation, fixup and setting, and enable and disable the bridge automatically.The enable and disable operations are split in
drm_bridge_funcs.pre_enable
,drm_bridge_funcs.enable
,drm_bridge_funcs.disable
anddrm_bridge_funcs.post_disable
to provide finer-grained control.Bridge drivers may implement the legacy version of those operations, or the atomic version (prefixed with atomic_), in which case they shall also implement the atomic state bookkeeping operations (
drm_bridge_funcs.atomic_duplicate_state
,drm_bridge_funcs.atomic_destroy_state
anddrm_bridge_funcs.reset
). Mixing atomic and non-atomic versions of the operations is not supported.The bus format negotiation operations
drm_bridge_funcs.atomic_get_output_bus_fmts
anddrm_bridge_funcs.atomic_get_input_bus_fmts
allow bridge drivers to negotiate the formats transmitted between bridges in the chain when multiple formats are supported. Negotiation for formats is performed transparently for display drivers by the atomic modeset helpers. Only atomic versions of those operations exist, bridge drivers that need to implement them shall thus also implement the atomic version of the encoder-related operations. This feature is not supported by the legacy CRTC helpers.The connector-related operations support implementing a
drm_connector
based on a chain of bridges. DRM bridges traditionally create adrm_connector
for bridges meant to be used at the end of the chain. This puts additional burden on bridge drivers, especially for bridges that may be used in the middle of a chain or at the end of it. Furthermore, it requires all operations of thedrm_connector
to be handled by a single bridge, which doesn’t always match the hardware architecture.To simplify bridge drivers and make the connector implementation more flexible, a new model allows bridges to unconditionally skip creation of
drm_connector
and instead exposedrm_bridge_funcs
operations to support an externally-implementeddrm_connector
. Those operations aredrm_bridge_funcs.detect
,drm_bridge_funcs.get_modes
,drm_bridge_funcs.get_edid
,drm_bridge_funcs.hpd_notify
,drm_bridge_funcs.hpd_enable
anddrm_bridge_funcs.hpd_disable
. When implemented, display drivers shall create adrm_connector
instance for each chain of bridges, and implement those connector instances based on the bridge connector operations.Bridge drivers shall implement the connector-related operations for all the features that the bridge hardware support. For instance, if a bridge supports reading EDID, the
drm_bridge_funcs.get_edid
shall be implemented. This however doesn’t mean that the DDC lines are wired to the bridge on a particular platform, as they could also be connected to an I2C controller of the SoC. Support for the connector-related operations on the running platform is reported through thedrm_bridge.ops
flags. Bridge drivers shall detect which operations they can support on the platform (usually this information is provided by ACPI or DT), and set thedrm_bridge.ops
flags for all supported operations. A flag shall only be set if the correspondingdrm_bridge_funcs
operation is implemented, but an implemented operation doesn’t necessarily imply that the corresponding flag will be set. Display drivers shall use thedrm_bridge.ops
flags to decide which bridge to delegate a connector operation to. This mechanism allows providing a single static constdrm_bridge_funcs
instance in bridge drivers, improving security by storing function pointers in read-only memory.In order to ease transition, bridge drivers may support both the old and new models by making connector creation optional and implementing the connected-related bridge operations. Connector creation is then controlled by the flags argument to the
drm_bridge_attach()
function. Display drivers that support the new model and create connectors themselves shall set theDRM_BRIDGE_ATTACH_NO_CONNECTOR
flag, and bridge drivers shall then skip connector creation. For intermediate bridges in the chain, the flag shall be passed to thedrm_bridge_attach()
call for the downstream bridge. Bridge drivers that implement the new model only shall return an error from theirdrm_bridge_funcs.attach
handler when theDRM_BRIDGE_ATTACH_NO_CONNECTOR
flag is not set. New display drivers should use the new model, and convert the bridge drivers they use if needed, in order to gradually transition to the new model.
Bridge Connector Helper¶
The DRM bridge connector helper object provides a DRM connector
implementation that wraps a chain of struct drm_bridge
. The connector
operations are fully implemented based on the operations of the bridges in
the chain, and don’t require any intervention from the display controller
driver at runtime.
To use the helper, display controller drivers create a bridge connector with
a call to drm_bridge_connector_init()
. This associates the newly created
connector with the chain of bridges passed to the function and registers it
with the DRM device. At that point the connector becomes fully usable, no
further operation is needed.
The DRM bridge connector operations are implemented based on the operations provided by the bridges in the chain. Each connector operation is delegated to the bridge closest to the connector (at the end of the chain) that provides the relevant functionality.
To make use of this helper, all bridges in the chain shall report bridge
operation flags (drm_bridge->ops
) and bridge output type
(drm_bridge->type
), as well as the DRM_BRIDGE_ATTACH_NO_CONNECTOR attach
flag (none of the bridges shall create a DRM connector directly).
Bridge Helper Reference¶
-
enum
drm_bridge_attach_flags
¶ Flags for
drm_bridge_funcs.attach
Constants
DRM_BRIDGE_ATTACH_NO_CONNECTOR
- When this flag is set the bridge shall not create a drm_connector.
-
struct
drm_bridge_funcs
¶ drm_bridge control functions
Definition
struct drm_bridge_funcs {
int (*attach)(struct drm_bridge *bridge, enum drm_bridge_attach_flags flags);
void (*detach)(struct drm_bridge *bridge);
enum drm_mode_status (*mode_valid)(struct drm_bridge *bridge,const struct drm_display_info *info, const struct drm_display_mode *mode);
bool (*mode_fixup)(struct drm_bridge *bridge,const struct drm_display_mode *mode, struct drm_display_mode *adjusted_mode);
void (*disable)(struct drm_bridge *bridge);
void (*post_disable)(struct drm_bridge *bridge);
void (*mode_set)(struct drm_bridge *bridge,const struct drm_display_mode *mode, const struct drm_display_mode *adjusted_mode);
void (*pre_enable)(struct drm_bridge *bridge);
void (*enable)(struct drm_bridge *bridge);
void (*atomic_pre_enable)(struct drm_bridge *bridge, struct drm_bridge_state *old_bridge_state);
void (*atomic_enable)(struct drm_bridge *bridge, struct drm_bridge_state *old_bridge_state);
void (*atomic_disable)(struct drm_bridge *bridge, struct drm_bridge_state *old_bridge_state);
void (*atomic_post_disable)(struct drm_bridge *bridge, struct drm_bridge_state *old_bridge_state);
struct drm_bridge_state *(*atomic_duplicate_state)(struct drm_bridge *bridge);
void (*atomic_destroy_state)(struct drm_bridge *bridge, struct drm_bridge_state *state);
u32 *(*atomic_get_output_bus_fmts)(struct drm_bridge *bridge,struct drm_bridge_state *bridge_state,struct drm_crtc_state *crtc_state,struct drm_connector_state *conn_state, unsigned int *num_output_fmts);
u32 *(*atomic_get_input_bus_fmts)(struct drm_bridge *bridge,struct drm_bridge_state *bridge_state,struct drm_crtc_state *crtc_state,struct drm_connector_state *conn_state,u32 output_fmt, unsigned int *num_input_fmts);
int (*atomic_check)(struct drm_bridge *bridge,struct drm_bridge_state *bridge_state,struct drm_crtc_state *crtc_state, struct drm_connector_state *conn_state);
struct drm_bridge_state *(*atomic_reset)(struct drm_bridge *bridge);
enum drm_connector_status (*detect)(struct drm_bridge *bridge);
int (*get_modes)(struct drm_bridge *bridge, struct drm_connector *connector);
struct edid *(*get_edid)(struct drm_bridge *bridge, struct drm_connector *connector);
void (*hpd_notify)(struct drm_bridge *bridge, enum drm_connector_status status);
void (*hpd_enable)(struct drm_bridge *bridge);
void (*hpd_disable)(struct drm_bridge *bridge);
};
Members
attach
This callback is invoked whenever our bridge is being attached to a
drm_encoder
. The flags argument tunes the behaviour of the attach operation (see DRM_BRIDGE_ATTACH_*).The attach callback is optional.
RETURNS:
Zero on success, error code on failure.
detach
This callback is invoked whenever our bridge is being detached from a
drm_encoder
.The detach callback is optional.
mode_valid
This callback is used to check if a specific mode is valid in this bridge. This should be implemented if the bridge has some sort of restriction in the modes it can display. For example, a given bridge may be responsible to set a clock value. If the clock can not produce all the values for the available modes then this callback can be used to restrict the number of modes to only the ones that can be displayed.
This hook is used by the probe helpers to filter the mode list in
drm_helper_probe_single_connector_modes()
, and it is used by the atomic helpers to validate modes supplied by userspace indrm_atomic_helper_check_modeset()
.The mode_valid callback is optional.
NOTE:
Since this function is both called from the check phase of an atomic commit, and the mode validation in the probe paths it is not allowed to look at anything else but the passed-in mode, and validate it against configuration-invariant hardward constraints. Any further limits which depend upon the configuration can only be checked in mode_fixup.
RETURNS:
drm_mode_status Enum
mode_fixup
This callback is used to validate and adjust a mode. The parameter mode is the display mode that should be fed to the next element in the display chain, either the final
drm_connector
or the nextdrm_bridge
. The parameter adjusted_mode is the input mode the bridge requires. It can be modified by this callback and does not need to match mode. See alsodrm_crtc_state.adjusted_mode
for more details.This is the only hook that allows a bridge to reject a modeset. If this function passes all other callbacks must succeed for this configuration.
The mode_fixup callback is optional.
drm_bridge_funcs.mode_fixup()
is not called whendrm_bridge_funcs.atomic_check()
is implemented, so only one of them should be provided.NOTE:
This function is called in the check phase of atomic modesets, which can be aborted for any reason (including on userspace’s request to just check whether a configuration would be possible). Drivers MUST NOT touch any persistent state (hardware or software) or data structures except the passed in state parameter.
Also beware that userspace can request its own custom modes, neither core nor helpers filter modes to the list of probe modes reported by the GETCONNECTOR IOCTL and stored in
drm_connector.modes
. To ensure that modes are filtered consistently put any bridge constraints and limits checks into mode_valid.RETURNS:
True if an acceptable configuration is possible, false if the modeset operation should be rejected.
disable
This callback should disable the bridge. It is called right before the preceding element in the display pipe is disabled. If the preceding element is a bridge this means it’s called before that bridge’s disable vfunc. If the preceding element is a
drm_encoder
it’s called right before thedrm_encoder_helper_funcs.disable
,drm_encoder_helper_funcs.prepare
ordrm_encoder_helper_funcs.dpms
hook.The bridge can assume that the display pipe (i.e. clocks and timing signals) feeding it is still running when this callback is called.
The disable callback is optional.
post_disable
This callback should disable the bridge. It is called right after the preceding element in the display pipe is disabled. If the preceding element is a bridge this means it’s called after that bridge’s post_disable function. If the preceding element is a
drm_encoder
it’s called right after the encoder’sdrm_encoder_helper_funcs.disable
,drm_encoder_helper_funcs.prepare
ordrm_encoder_helper_funcs.dpms
hook.The bridge must assume that the display pipe (i.e. clocks and timing singals) feeding it is no longer running when this callback is called.
The post_disable callback is optional.
mode_set
This callback should set the given mode on the bridge. It is called after the mode_set callback for the preceding element in the display pipeline has been called already. If the bridge is the first element then this would be
drm_encoder_helper_funcs.mode_set
. The display pipe (i.e. clocks and timing signals) is off when this function is called.The adjusted_mode parameter is the mode output by the CRTC for the first bridge in the chain. It can be different from the mode parameter that contains the desired mode for the connector at the end of the bridges chain, for instance when the first bridge in the chain performs scaling. The adjusted mode is mostly useful for the first bridge in the chain and is likely irrelevant for the other bridges.
For atomic drivers the adjusted_mode is the mode stored in
drm_crtc_state.adjusted_mode
.NOTE:
If a need arises to store and access modes adjusted for other locations than the connection between the CRTC and the first bridge, the DRM framework will have to be extended with DRM bridge states.
pre_enable
This callback should enable the bridge. It is called right before the preceding element in the display pipe is enabled. If the preceding element is a bridge this means it’s called before that bridge’s pre_enable function. If the preceding element is a
drm_encoder
it’s called right before the encoder’sdrm_encoder_helper_funcs.enable
,drm_encoder_helper_funcs.commit
ordrm_encoder_helper_funcs.dpms
hook.The display pipe (i.e. clocks and timing signals) feeding this bridge will not yet be running when this callback is called. The bridge must not enable the display link feeding the next bridge in the chain (if there is one) when this callback is called.
The pre_enable callback is optional.
enable
This callback should enable the bridge. It is called right after the preceding element in the display pipe is enabled. If the preceding element is a bridge this means it’s called after that bridge’s enable function. If the preceding element is a
drm_encoder
it’s called right after the encoder’sdrm_encoder_helper_funcs.enable
,drm_encoder_helper_funcs.commit
ordrm_encoder_helper_funcs.dpms
hook.The bridge can assume that the display pipe (i.e. clocks and timing signals) feeding it is running when this callback is called. This callback must enable the display link feeding the next bridge in the chain if there is one.
The enable callback is optional.
atomic_pre_enable
This callback should enable the bridge. It is called right before the preceding element in the display pipe is enabled. If the preceding element is a bridge this means it’s called before that bridge’s atomic_pre_enable or pre_enable function. If the preceding element is a
drm_encoder
it’s called right before the encoder’sdrm_encoder_helper_funcs.atomic_enable
hook.The display pipe (i.e. clocks and timing signals) feeding this bridge will not yet be running when this callback is called. The bridge must not enable the display link feeding the next bridge in the chain (if there is one) when this callback is called.
Note that this function will only be invoked in the context of an atomic commit. It will not be invoked from
drm_bridge_chain_pre_enable
. It would be prudent to also provide an implementation of pre_enable if you are expecting driver calls intodrm_bridge_chain_pre_enable
.The atomic_pre_enable callback is optional.
atomic_enable
This callback should enable the bridge. It is called right after the preceding element in the display pipe is enabled. If the preceding element is a bridge this means it’s called after that bridge’s atomic_enable or enable function. If the preceding element is a
drm_encoder
it’s called right after the encoder’sdrm_encoder_helper_funcs.atomic_enable
hook.The bridge can assume that the display pipe (i.e. clocks and timing signals) feeding it is running when this callback is called. This callback must enable the display link feeding the next bridge in the chain if there is one.
Note that this function will only be invoked in the context of an atomic commit. It will not be invoked from
drm_bridge_chain_enable
. It would be prudent to also provide an implementation of enable if you are expecting driver calls intodrm_bridge_chain_enable
.The atomic_enable callback is optional.
atomic_disable
This callback should disable the bridge. It is called right before the preceding element in the display pipe is disabled. If the preceding element is a bridge this means it’s called before that bridge’s atomic_disable or disable vfunc. If the preceding element is a
drm_encoder
it’s called right before thedrm_encoder_helper_funcs.atomic_disable
hook.The bridge can assume that the display pipe (i.e. clocks and timing signals) feeding it is still running when this callback is called.
Note that this function will only be invoked in the context of an atomic commit. It will not be invoked from
drm_bridge_chain_disable
. It would be prudent to also provide an implementation of disable if you are expecting driver calls intodrm_bridge_chain_disable
.The atomic_disable callback is optional.
atomic_post_disable
This callback should disable the bridge. It is called right after the preceding element in the display pipe is disabled. If the preceding element is a bridge this means it’s called after that bridge’s atomic_post_disable or post_disable function. If the preceding element is a
drm_encoder
it’s called right after the encoder’sdrm_encoder_helper_funcs.atomic_disable
hook.The bridge must assume that the display pipe (i.e. clocks and timing signals) feeding it is no longer running when this callback is called.
Note that this function will only be invoked in the context of an atomic commit. It will not be invoked from
drm_bridge_chain_post_disable
. It would be prudent to also provide an implementation of post_disable if you are expecting driver calls intodrm_bridge_chain_post_disable
.The atomic_post_disable callback is optional.
atomic_duplicate_state
Duplicate the current bridge state object (which is guaranteed to be non-NULL).
The atomic_duplicate_state hook is mandatory if the bridge implements any of the atomic hooks, and should be left unassigned otherwise. For bridges that don’t subclass
drm_bridge_state
, thedrm_atomic_helper_bridge_duplicate_state()
helper function shall be used to implement this hook.RETURNS: A valid drm_bridge_state object or NULL if the allocation fails.
atomic_destroy_state
Destroy a bridge state object previously allocated by
drm_bridge_funcs.atomic_duplicate_state()
.The atomic_destroy_state hook is mandatory if the bridge implements any of the atomic hooks, and should be left unassigned otherwise. For bridges that don’t subclass
drm_bridge_state
, thedrm_atomic_helper_bridge_destroy_state()
helper function shall be used to implement this hook.atomic_get_output_bus_fmts
Return the supported bus formats on the output end of a bridge. The returned array must be allocated with
kmalloc()
and will be freed by the caller. If the allocation fails, NULL should be returned. num_output_fmts must be set to the returned array size. Formats listed in the returned array should be listed in decreasing preference order (the core will try all formats until it finds one that works).This method is only called on the last element of the bridge chain as part of the bus format negotiation process that happens in
drm_atomic_bridge_chain_select_bus_fmts`(). This method is optional. When not implemented, the core will fall back to :c:type:`drm_connector.display_info
.bus_formats[0] ifdrm_connector.display_info
.num_bus_formats > 0, or to MEDIA_BUS_FMT_FIXED otherwise.atomic_get_input_bus_fmts
Return the supported bus formats on the input end of a bridge for a specific output bus format.
The returned array must be allocated with
kmalloc()
and will be freed by the caller. If the allocation fails, NULL should be returned. num_output_fmts must be set to the returned array size. Formats listed in the returned array should be listed in decreasing preference order (the core will try all formats until it finds one that works). When the format is not supported NULL should be returned and num_output_fmts should be set to 0.This method is called on all elements of the bridge chain as part of the bus format negotiation process that happens in drm_atomic_bridge_chain_select_bus_fmts(). This method is optional. When not implemented, the core will bypass bus format negotiation on this element of the bridge without failing, and the previous element in the chain will be passed MEDIA_BUS_FMT_FIXED as its output bus format.
Bridge drivers that need to support being linked to bridges that are not supporting bus format negotiation should handle the output_fmt == MEDIA_BUS_FMT_FIXED case appropriately, by selecting a sensible default value or extracting this information from somewhere else (FW property,
drm_display_mode
,drm_display_info
, …)Note: Even if input format selection on the first bridge has no impact on the negotiation process (bus format negotiation stops once we reach the first element of the chain), drivers are expected to return accurate input formats as the input format may be used to configure the CRTC output appropriately.
atomic_check
This method is responsible for checking bridge state correctness. It can also check the state of the surrounding components in chain to make sure the whole pipeline can work properly.
drm_bridge_funcs.atomic_check()
hooks are called in reverse order (from the last to the first bridge).This method is optional.
drm_bridge_funcs.mode_fixup()
is not called whendrm_bridge_funcs.atomic_check()
is implemented, so only one of them should be provided.If drivers need to tweak
drm_bridge_state.input_bus_cfg
.flags ordrm_bridge_state.output_bus_cfg
.flags it should happen in this function. By default thedrm_bridge_state.output_bus_cfg
.flags field is set to the next bridgedrm_bridge_state.input_bus_cfg
.flags value ordrm_connector.display_info
.bus_flags if the bridge is the last element in the chain.RETURNS: zero if the check passed, a negative error code otherwise.
atomic_reset
Reset the bridge to a predefined state (or retrieve its current state) and return a
drm_bridge_state
object matching this state. This function is called at attach time.The atomic_reset hook is mandatory if the bridge implements any of the atomic hooks, and should be left unassigned otherwise. For bridges that don’t subclass
drm_bridge_state
, thedrm_atomic_helper_bridge_reset()
helper function shall be used to implement this hook.Note that the atomic_reset() semantics is not exactly matching the reset() semantics found on other components (connector, plane, …).
- The reset operation happens when the bridge is attached, not when
drm_mode_config_reset()
is called - It’s meant to be used exclusively on bridges that have been converted to the ATOMIC API
RETURNS: A valid drm_bridge_state object in case of success, an ERR_PTR() giving the reason of the failure otherwise.
- The reset operation happens when the bridge is attached, not when
detect
Check if anything is attached to the bridge output.
This callback is optional, if not implemented the bridge will be considered as always having a component attached to its output. Bridges that implement this callback shall set the DRM_BRIDGE_OP_DETECT flag in their
drm_bridge->ops
.RETURNS:
drm_connector_status indicating the bridge output status.
get_modes
Fill all modes currently valid for the sink into the
drm_connector
withdrm_mode_probed_add()
.The get_modes callback is mostly intended to support non-probeable displays such as many fixed panels. Bridges that support reading EDID shall leave get_modes unimplemented and implement the
drm_bridge_funcs->get_edid
callback instead.This callback is optional. Bridges that implement it shall set the DRM_BRIDGE_OP_MODES flag in their
drm_bridge->ops
.The connector parameter shall be used for the sole purpose of filling modes, and shall not be stored internally by bridge drivers for future usage.
RETURNS:
The number of modes added by calling
drm_mode_probed_add()
.get_edid
Read and parse the EDID data of the connected display.
The get_edid callback is the preferred way of reporting mode information for a display connected to the bridge output. Bridges that support reading EDID shall implement this callback and leave the get_modes callback unimplemented.
The caller of this operation shall first verify the output connection status and refrain from reading EDID from a disconnected output.
This callback is optional. Bridges that implement it shall set the DRM_BRIDGE_OP_EDID flag in their
drm_bridge->ops
.The connector parameter shall be used for the sole purpose of EDID retrieval and parsing, and shall not be stored internally by bridge drivers for future usage.
RETURNS:
An edid structure newly allocated with
kmalloc()
(or similar) on success, or NULL otherwise. The caller is responsible for freeing the returned edid structure withkfree()
.hpd_notify
Notify the bridge of hot plug detection.
This callback is optional, it may be implemented by bridges that need to be notified of display connection or disconnection for internal reasons. One use case is to reset the internal state of CEC controllers for HDMI bridges.
hpd_enable
Enable hot plug detection. From now on the bridge shall call
drm_bridge_hpd_notify()
each time a change is detected in the output connection status, until hot plug detection gets disabled with hpd_disable.This callback is optional and shall only be implemented by bridges that support hot-plug notification without polling. Bridges that implement it shall also implement the hpd_disable callback and set the DRM_BRIDGE_OP_HPD flag in their
drm_bridge->ops
.hpd_disable
Disable hot plug detection. Once this function returns the bridge shall not call
drm_bridge_hpd_notify()
when a change in the output connection status occurs.This callback is optional and shall only be implemented by bridges that support hot-plug notification without polling. Bridges that implement it shall also implement the hpd_enable callback and set the DRM_BRIDGE_OP_HPD flag in their
drm_bridge->ops
.
-
struct
drm_bridge_timings
¶ timing information for the bridge
Definition
struct drm_bridge_timings {
u32 input_bus_flags;
u32 setup_time_ps;
u32 hold_time_ps;
bool dual_link;
};
Members
input_bus_flags
- Tells what additional settings for the pixel data on the bus
this bridge requires (like pixel signal polarity). See also
drm_display_info->bus_flags
. setup_time_ps
- Defines the time in picoseconds the input data lines must be stable before the clock edge.
hold_time_ps
- Defines the time in picoseconds taken for the bridge to sample the input signal after the clock edge.
dual_link
- True if the bus operates in dual-link mode. The exact meaning is dependent on the bus type. For LVDS buses, this indicates that even- and odd-numbered pixels are received on separate links.
-
enum
drm_bridge_ops
¶ Bitmask of operations supported by the bridge
Constants
DRM_BRIDGE_OP_DETECT
- The bridge can detect displays connected to
its output. Bridges that set this flag shall implement the
drm_bridge_funcs->detect
callback. DRM_BRIDGE_OP_EDID
- The bridge can retrieve the EDID of the display
connected to its output. Bridges that set this flag shall implement
the
drm_bridge_funcs->get_edid
callback. DRM_BRIDGE_OP_HPD
- The bridge can detect hot-plug and hot-unplug
without requiring polling. Bridges that set this flag shall
implement the
drm_bridge_funcs->hpd_enable
anddrm_bridge_funcs->hpd_disable
callbacks if they support enabling and disabling hot-plug detection dynamically. DRM_BRIDGE_OP_MODES
- The bridge can retrieve the modes supported
by the display at its output. This does not include reading EDID
which is separately covered by DRM_BRIDGE_OP_EDID. Bridges that set
this flag shall implement the
drm_bridge_funcs->get_modes
callback.
-
struct
drm_bridge
¶ central DRM bridge control structure
Definition
struct drm_bridge {
struct drm_private_obj base;
struct drm_device *dev;
struct drm_encoder *encoder;
struct list_head chain_node;
#ifdef CONFIG_OF;
struct device_node *of_node;
#endif;
struct list_head list;
const struct drm_bridge_timings *timings;
const struct drm_bridge_funcs *funcs;
void *driver_private;
enum drm_bridge_ops ops;
int type;
bool interlace_allowed;
struct i2c_adapter *ddc;
struct mutex hpd_mutex;
void (*hpd_cb)(void *data, enum drm_connector_status status);
void *hpd_data;
};
Members
base
- inherit from
drm_private_object
dev
- DRM device this bridge belongs to
encoder
- encoder to which this bridge is connected
chain_node
- used to form a bridge chain
of_node
- device node pointer to the bridge
list
- to keep track of all added bridges
timings
- the timing specification for the bridge, if any (may be NULL)
funcs
- control functions
driver_private
- pointer to the bridge driver’s internal context
ops
- bitmask of operations supported by the bridge
type
- Type of the connection at the bridge output (DRM_MODE_CONNECTOR_*). For bridges at the end of this chain this identifies the type of connected display.
interlace_allowed
- Indicate that the bridge can handle interlaced modes.
ddc
- Associated I2C adapter for DDC access, if any.
hpd_mutex
- Protects the hpd_cb and hpd_data fields.
hpd_cb
- Hot plug detection callback, registered with
drm_bridge_hpd_enable()
. hpd_data
- Private data passed to the Hot plug detection callback hpd_cb.
-
struct drm_bridge *
drm_bridge_get_next_bridge
(struct drm_bridge *bridge)¶ Get the next bridge in the chain
Parameters
struct drm_bridge *bridge
- bridge object
Return
the next bridge in the chain after bridge, or NULL if bridge is the last.
-
struct drm_bridge *
drm_bridge_get_prev_bridge
(struct drm_bridge *bridge)¶ Get the previous bridge in the chain
Parameters
struct drm_bridge *bridge
- bridge object
Return
the previous bridge in the chain, or NULL if bridge is the first.
-
struct drm_bridge *
drm_bridge_chain_get_first_bridge
(struct drm_encoder *encoder)¶ Get the first bridge in the chain
Parameters
struct drm_encoder *encoder
- encoder object
Return
the first bridge in the chain, or NULL if encoder has no bridge attached to it.
-
drm_for_each_bridge_in_chain
(encoder, bridge)¶ Iterate over all bridges present in a chain
Parameters
encoder
- the encoder to iterate bridges on
bridge
- a bridge pointer updated to point to the current bridge at each iteration
Description
Iterate over all bridges present in the bridge chain attached to encoder.
-
void
drm_bridge_add
(struct drm_bridge *bridge)¶ add the given bridge to the global bridge list
Parameters
struct drm_bridge *bridge
- bridge control structure
-
void
drm_bridge_remove
(struct drm_bridge *bridge)¶ remove the given bridge from the global bridge list
Parameters
struct drm_bridge *bridge
- bridge control structure
-
int
drm_bridge_attach
(struct drm_encoder *encoder, struct drm_bridge *bridge, struct drm_bridge *previous, enum drm_bridge_attach_flags flags)¶ attach the bridge to an encoder’s chain
Parameters
struct drm_encoder *encoder
- DRM encoder
struct drm_bridge *bridge
- bridge to attach
struct drm_bridge *previous
- previous bridge in the chain (optional)
enum drm_bridge_attach_flags flags
- DRM_BRIDGE_ATTACH_* flags
Description
Called by a kms driver to link the bridge to an encoder’s chain. The previous argument specifies the previous bridge in the chain. If NULL, the bridge is linked directly at the encoder’s output. Otherwise it is linked at the previous bridge’s output.
If non-NULL the previous bridge must be already attached by a call to this function.
Note that bridges attached to encoders are auto-detached during encoder
cleanup in drm_encoder_cleanup()
, so drm_bridge_attach()
should generally
not be balanced with a drm_bridge_detach() in driver code.
Return
Zero on success, error code on failure
-
bool
drm_bridge_chain_mode_fixup
(struct drm_bridge *bridge, const struct drm_display_mode *mode, struct drm_display_mode *adjusted_mode)¶ fixup proposed mode for all bridges in the encoder chain
Parameters
struct drm_bridge *bridge
- bridge control structure
const struct drm_display_mode *mode
- desired mode to be set for the bridge
struct drm_display_mode *adjusted_mode
- updated mode that works for this bridge
Description
Calls drm_bridge_funcs.mode_fixup
for all the bridges in the
encoder chain, starting from the first bridge to the last.
Note
the bridge passed should be the one closest to the encoder
Return
true on success, false on failure
-
enum drm_mode_status
drm_bridge_chain_mode_valid
(struct drm_bridge *bridge, const struct drm_display_info *info, const struct drm_display_mode *mode)¶ validate the mode against all bridges in the encoder chain.
Parameters
struct drm_bridge *bridge
- bridge control structure
const struct drm_display_info *info
- display info against which the mode shall be validated
const struct drm_display_mode *mode
- desired mode to be validated
Description
Calls drm_bridge_funcs.mode_valid
for all the bridges in the encoder
chain, starting from the first bridge to the last. If at least one bridge
does not accept the mode the function returns the error code.
Note
the bridge passed should be the one closest to the encoder.
Return
MODE_OK on success, drm_mode_status Enum error code on failure
-
void
drm_bridge_chain_disable
(struct drm_bridge *bridge)¶ disables all bridges in the encoder chain
Parameters
struct drm_bridge *bridge
- bridge control structure
Description
Calls drm_bridge_funcs.disable
op for all the bridges in the encoder
chain, starting from the last bridge to the first. These are called before
calling the encoder’s prepare op.
Note
the bridge passed should be the one closest to the encoder
-
void
drm_bridge_chain_post_disable
(struct drm_bridge *bridge)¶ cleans up after disabling all bridges in the encoder chain
Parameters
struct drm_bridge *bridge
- bridge control structure
Description
Calls drm_bridge_funcs.post_disable
op for all the bridges in the
encoder chain, starting from the first bridge to the last. These are called
after completing the encoder’s prepare op.
Note
the bridge passed should be the one closest to the encoder
-
void
drm_bridge_chain_mode_set
(struct drm_bridge *bridge, const struct drm_display_mode *mode, const struct drm_display_mode *adjusted_mode)¶ set proposed mode for all bridges in the encoder chain
Parameters
struct drm_bridge *bridge
- bridge control structure
const struct drm_display_mode *mode
- desired mode to be set for the encoder chain
const struct drm_display_mode *adjusted_mode
- updated mode that works for this encoder chain
Description
Calls drm_bridge_funcs.mode_set
op for all the bridges in the
encoder chain, starting from the first bridge to the last.
Note
the bridge passed should be the one closest to the encoder
-
void
drm_bridge_chain_pre_enable
(struct drm_bridge *bridge)¶ prepares for enabling all bridges in the encoder chain
Parameters
struct drm_bridge *bridge
- bridge control structure
Description
Calls drm_bridge_funcs.pre_enable
op for all the bridges in the encoder
chain, starting from the last bridge to the first. These are called
before calling the encoder’s commit op.
Note
the bridge passed should be the one closest to the encoder
-
void
drm_bridge_chain_enable
(struct drm_bridge *bridge)¶ enables all bridges in the encoder chain
Parameters
struct drm_bridge *bridge
- bridge control structure
Description
Calls drm_bridge_funcs.enable
op for all the bridges in the encoder
chain, starting from the first bridge to the last. These are called
after completing the encoder’s commit op.
Note that the bridge passed should be the one closest to the encoder
-
void
drm_atomic_bridge_chain_disable
(struct drm_bridge *bridge, struct drm_atomic_state *old_state)¶ disables all bridges in the encoder chain
Parameters
struct drm_bridge *bridge
- bridge control structure
struct drm_atomic_state *old_state
- old atomic state
Description
Calls drm_bridge_funcs.atomic_disable
(falls back on
drm_bridge_funcs.disable
) op for all the bridges in the encoder chain,
starting from the last bridge to the first. These are called before calling
drm_encoder_helper_funcs.atomic_disable
Note
the bridge passed should be the one closest to the encoder
-
void
drm_atomic_bridge_chain_post_disable
(struct drm_bridge *bridge, struct drm_atomic_state *old_state)¶ cleans up after disabling all bridges in the encoder chain
Parameters
struct drm_bridge *bridge
- bridge control structure
struct drm_atomic_state *old_state
- old atomic state
Description
Calls drm_bridge_funcs.atomic_post_disable
(falls back on
drm_bridge_funcs.post_disable
) op for all the bridges in the encoder chain,
starting from the first bridge to the last. These are called after completing
drm_encoder_helper_funcs.atomic_disable
Note
the bridge passed should be the one closest to the encoder
-
void
drm_atomic_bridge_chain_pre_enable
(struct drm_bridge *bridge, struct drm_atomic_state *old_state)¶ prepares for enabling all bridges in the encoder chain
Parameters
struct drm_bridge *bridge
- bridge control structure
struct drm_atomic_state *old_state
- old atomic state
Description
Calls drm_bridge_funcs.atomic_pre_enable
(falls back on
drm_bridge_funcs.pre_enable
) op for all the bridges in the encoder chain,
starting from the last bridge to the first. These are called before calling
drm_encoder_helper_funcs.atomic_enable
Note
the bridge passed should be the one closest to the encoder
-
void
drm_atomic_bridge_chain_enable
(struct drm_bridge *bridge, struct drm_atomic_state *old_state)¶ enables all bridges in the encoder chain
Parameters
struct drm_bridge *bridge
- bridge control structure
struct drm_atomic_state *old_state
- old atomic state
Description
Calls drm_bridge_funcs.atomic_enable
(falls back on
drm_bridge_funcs.enable
) op for all the bridges in the encoder chain,
starting from the first bridge to the last. These are called after completing
drm_encoder_helper_funcs.atomic_enable
Note
the bridge passed should be the one closest to the encoder
-
int
drm_atomic_bridge_chain_check
(struct drm_bridge *bridge, struct drm_crtc_state *crtc_state, struct drm_connector_state *conn_state)¶ Do an atomic check on the bridge chain
Parameters
struct drm_bridge *bridge
- bridge control structure
struct drm_crtc_state *crtc_state
- new CRTC state
struct drm_connector_state *conn_state
- new connector state
Description
First trigger a bus format negotiation before calling
drm_bridge_funcs.atomic_check()
(falls back on
drm_bridge_funcs.mode_fixup()
) op for all the bridges in the encoder chain,
starting from the last bridge to the first. These are called before calling
drm_encoder_helper_funcs.atomic_check()
Return
0 on success, a negative error code on failure
-
enum drm_connector_status
drm_bridge_detect
(struct drm_bridge *bridge)¶ check if anything is attached to the bridge output
Parameters
struct drm_bridge *bridge
- bridge control structure
Description
If the bridge supports output detection, as reported by the
DRM_BRIDGE_OP_DETECT bridge ops flag, call drm_bridge_funcs.detect
for the
bridge and return the connection status. Otherwise return
connector_status_unknown.
Return
The detection status on success, or connector_status_unknown if the bridge doesn’t support output detection.
-
int
drm_bridge_get_modes
(struct drm_bridge *bridge, struct drm_connector *connector)¶ fill all modes currently valid for the sink into the connector
Parameters
struct drm_bridge *bridge
- bridge control structure
struct drm_connector *connector
- the connector to fill with modes
Description
If the bridge supports output modes retrieval, as reported by the
DRM_BRIDGE_OP_MODES bridge ops flag, call drm_bridge_funcs.get_modes
to
fill the connector with all valid modes and return the number of modes
added. Otherwise return 0.
Return
The number of modes added to the connector.
-
struct edid *
drm_bridge_get_edid
(struct drm_bridge *bridge, struct drm_connector *connector)¶ get the EDID data of the connected display
Parameters
struct drm_bridge *bridge
- bridge control structure
struct drm_connector *connector
- the connector to read EDID for
Description
If the bridge supports output EDID retrieval, as reported by the
DRM_BRIDGE_OP_EDID bridge ops flag, call drm_bridge_funcs.get_edid
to
get the EDID and return it. Otherwise return NULL.
Return
The retrieved EDID on success, or NULL otherwise.
-
void
drm_bridge_hpd_enable
(struct drm_bridge *bridge, void (*cb)(void *data, enum drm_connector_status status), void *data)¶ enable hot plug detection for the bridge
Parameters
struct drm_bridge *bridge
- bridge control structure
void (*cb)(void *data, enum drm_connector_status status)
- hot-plug detection callback
void *data
- data to be passed to the hot-plug detection callback
Description
Call drm_bridge_funcs.hpd_enable
if implemented and register the given cb
and data as hot plug notification callback. From now on the cb will be
called with data when an output status change is detected by the bridge,
until hot plug notification gets disabled with drm_bridge_hpd_disable()
.
Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in bridge->ops. This function shall not be called when the flag is not set.
Only one hot plug detection callback can be registered at a time, it is an error to call this function when hot plug detection is already enabled for the bridge.
-
void
drm_bridge_hpd_disable
(struct drm_bridge *bridge)¶ disable hot plug detection for the bridge
Parameters
struct drm_bridge *bridge
- bridge control structure
Description
Call drm_bridge_funcs.hpd_disable
if implemented and unregister the hot
plug detection callback previously registered with drm_bridge_hpd_enable()
.
Once this function returns the callback will not be called by the bridge
when an output status change occurs.
Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in bridge->ops. This function shall not be called when the flag is not set.
-
void
drm_bridge_hpd_notify
(struct drm_bridge *bridge, enum drm_connector_status status)¶ notify hot plug detection events
Parameters
struct drm_bridge *bridge
- bridge control structure
enum drm_connector_status status
- output connection status
Description
Bridge drivers shall call this function to report hot plug events when they
detect a change in the output status, when hot plug detection has been
enabled by drm_bridge_hpd_enable()
.
This function shall be called in a context that can sleep.
-
struct drm_bridge *
of_drm_find_bridge
(struct device_node *np)¶ find the bridge corresponding to the device node in the global bridge list
Parameters
struct device_node *np
- device node
Return
drm_bridge control struct on success, NULL on failure
Bridge Connector Helper Reference¶
-
void
drm_bridge_connector_enable_hpd
(struct drm_connector *connector)¶ Enable hot-plug detection for the connector
Parameters
struct drm_connector *connector
- The DRM bridge connector
Description
This function enables hot-plug detection for the given bridge connector. This is typically used by display drivers in their resume handler.
-
void
drm_bridge_connector_disable_hpd
(struct drm_connector *connector)¶ Disable hot-plug detection for the connector
Parameters
struct drm_connector *connector
- The DRM bridge connector
Description
This function disables hot-plug detection for the given bridge connector. This is typically used by display drivers in their suspend handler.
-
struct drm_connector *
drm_bridge_connector_init
(struct drm_device *drm, struct drm_encoder *encoder)¶ Initialise a connector for a chain of bridges
Parameters
struct drm_device *drm
- the DRM device
struct drm_encoder *encoder
- the encoder where the bridge chain starts
Description
Allocate, initialise and register a drm_bridge_connector
with the drm
device. The connector is associated with a chain of bridges that starts at
the encoder. All bridges in the chain shall report bridge operation flags
(drm_bridge->ops
) and bridge output type (drm_bridge->type
), and none of
them may create a DRM connector directly.
Returns a pointer to the new connector on success, or a negative error pointer otherwise.
Panel-Bridge Helper Reference¶
-
struct drm_bridge *
drm_panel_bridge_add
(struct drm_panel *panel)¶ Creates a
drm_bridge
anddrm_connector
that just calls the appropriate functions fromdrm_panel
.
Parameters
struct drm_panel *panel
- The drm_panel being wrapped. Must be non-NULL.
Description
For drivers converting from directly using drm_panel: The expected
usage pattern is that during either encoder module probe or DSI
host attach, a drm_panel will be looked up through
drm_of_find_panel_or_bridge()
. drm_panel_bridge_add()
is used to
wrap that panel in the new bridge, and the result can then be
passed to drm_bridge_attach()
. The drm_panel_prepare()
and related
functions can be dropped from the encoder driver (they’re now
called by the KMS helpers before calling into the encoder), along
with connector creation. When done with the bridge (after
drm_mode_config_cleanup()
if the bridge has already been attached), then
drm_panel_bridge_remove()
to free it.
The connector type is set to panel->connector_type, which must be set to a known type. Calling this function with a panel whose connector type is DRM_MODE_CONNECTOR_Unknown will return ERR_PTR(-EINVAL).
See devm_drm_panel_bridge_add()
for an automatically managed version of this
function.
-
struct drm_bridge *
drm_panel_bridge_add_typed
(struct drm_panel *panel, u32 connector_type)¶ Creates a
drm_bridge
anddrm_connector
with an explicit connector type.
Parameters
struct drm_panel *panel
- The drm_panel being wrapped. Must be non-NULL.
u32 connector_type
- The connector type (DRM_MODE_CONNECTOR_*)
Description
This is just like drm_panel_bridge_add()
, but forces the connector type to
connector_type instead of infering it from the panel.
This function is deprecated and should not be used in new drivers. Use
drm_panel_bridge_add()
instead, and fix panel drivers as necessary if they
don’t report a connector type.
-
void
drm_panel_bridge_remove
(struct drm_bridge *bridge)¶ Unregisters and frees a drm_bridge created by
drm_panel_bridge_add()
.
Parameters
struct drm_bridge *bridge
- The drm_bridge being freed.
-
struct drm_bridge *
devm_drm_panel_bridge_add
(struct device *dev, struct drm_panel *panel)¶ Creates a managed
drm_bridge
anddrm_connector
that just calls the appropriate functions fromdrm_panel
.
Parameters
struct device *dev
- device to tie the bridge lifetime to
struct drm_panel *panel
- The drm_panel being wrapped. Must be non-NULL.
Description
This is the managed version of drm_panel_bridge_add()
which automatically
calls drm_panel_bridge_remove()
when dev is unbound.
-
struct drm_bridge *
devm_drm_panel_bridge_add_typed
(struct device *dev, struct drm_panel *panel, u32 connector_type)¶ Creates a managed
drm_bridge
anddrm_connector
with an explicit connector type.
Parameters
struct device *dev
- device to tie the bridge lifetime to
struct drm_panel *panel
- The drm_panel being wrapped. Must be non-NULL.
u32 connector_type
- The connector type (DRM_MODE_CONNECTOR_*)
Description
This is just like devm_drm_panel_bridge_add()
, but forces the connector type
to connector_type instead of infering it from the panel.
This function is deprecated and should not be used in new drivers. Use
devm_drm_panel_bridge_add()
instead, and fix panel drivers as necessary if
they don’t report a connector type.
-
struct drm_connector *
drm_panel_bridge_connector
(struct drm_bridge *bridge)¶ return the connector for the panel bridge
Parameters
struct drm_bridge *bridge
- The drm_bridge.
Description
drm_panel_bridge creates the connector. This function gives external access to the connector.
Return
Pointer to drm_connector
Panel Helper Reference¶
The DRM panel helpers allow drivers to register panel objects with a central registry and provide functions to retrieve those panels in display drivers.
For easy integration into drivers using the drm_bridge
infrastructure please
take look at drm_panel_bridge_add()
and devm_drm_panel_bridge_add()
.
-
struct
drm_panel_funcs
¶ perform operations on a given panel
Definition
struct drm_panel_funcs {
int (*prepare)(struct drm_panel *panel);
int (*enable)(struct drm_panel *panel);
int (*disable)(struct drm_panel *panel);
int (*unprepare)(struct drm_panel *panel);
int (*get_modes)(struct drm_panel *panel, struct drm_connector *connector);
int (*get_timings)(struct drm_panel *panel, unsigned int num_timings, struct display_timing *timings);
};
Members
prepare
Turn on panel and perform set up.
This function is optional.
enable
Enable panel (turn on back light, etc.).
This function is optional.
disable
Disable panel (turn off back light, etc.).
This function is optional.
unprepare
Turn off panel.
This function is optional.
get_modes
Add modes to the connector that the panel is attached to and returns the number of modes added.
This function is mandatory.
get_timings
Copy display timings into the provided array and return the number of display timings available.
This function is optional.
Description
The .prepare() function is typically called before the display controller starts to transmit video data. Panel drivers can use this to turn the panel on and wait for it to become ready. If additional configuration is required (via a control bus such as I2C, SPI or DSI for example) this is a good time to do that.
After the display controller has started transmitting video data, it’s safe to call the .enable() function. This will typically enable the backlight to make the image on screen visible. Some panels require a certain amount of time or frames before the image is displayed. This function is responsible for taking this into account before enabling the backlight to avoid visual glitches.
Before stopping video transmission from the display controller it can be necessary to turn off the panel to avoid visual glitches. This is done in the .disable() function. Analogously to .enable() this typically involves turning off the backlight and waiting for some time to make sure no image is visible on the panel. It is then safe for the display controller to cease transmission of video data.
To save power when no video data is transmitted, a driver can power down the panel. This is the job of the .unprepare() function.
Backlight can be handled automatically if configured using
drm_panel_of_backlight()
. Then the driver does not need to implement the
functionality to enable/disable backlight.
-
struct
drm_panel
¶ DRM panel object
Definition
struct drm_panel {
struct device *dev;
struct backlight_device *backlight;
const struct drm_panel_funcs *funcs;
int connector_type;
struct list_head list;
};
Members
dev
- Parent device of the panel.
backlight
- Backlight device, used to turn on backlight after the call
to enable(), and to turn off backlight before the call to
disable().
backlight is set by
drm_panel_of_backlight()
and drivers shall not assign it. funcs
- Operations that can be performed on the panel.
connector_type
- Type of the panel as a DRM_MODE_CONNECTOR_* value. This is used to initialise the drm_connector corresponding to the panel with the correct connector type.
list
- Panel entry in registry.
-
void
drm_panel_init
(struct drm_panel *panel, struct device *dev, const struct drm_panel_funcs *funcs, int connector_type)¶ initialize a panel
Parameters
struct drm_panel *panel
- DRM panel
struct device *dev
- parent device of the panel
const struct drm_panel_funcs *funcs
- panel operations
int connector_type
- the connector type (DRM_MODE_CONNECTOR_*) corresponding to the panel interface
Description
Initialize the panel structure for subsequent registration with
drm_panel_add()
.
Parameters
struct drm_panel *panel
- panel to add
Description
Add a panel to the global registry so that it can be looked up by display drivers.
Parameters
struct drm_panel *panel
- DRM panel
Description
Removes a panel from the global registry.
Parameters
struct drm_panel *panel
- DRM panel
Description
Calling this function will enable power and deassert any reset signals to the panel. After this has completed it is possible to communicate with any integrated circuitry via a command bus.
Return
0 on success or a negative error code on failure.
Parameters
struct drm_panel *panel
- DRM panel
Description
Calling this function will completely power off a panel (assert the panel’s
reset, turn off power supplies, …). After this function has completed, it
is usually no longer possible to communicate with the panel until another
call to drm_panel_prepare()
.
Return
0 on success or a negative error code on failure.
Parameters
struct drm_panel *panel
- DRM panel
Description
Calling this function will cause the panel display drivers to be turned on and the backlight to be enabled. Content will be visible on screen after this call completes.
Return
0 on success or a negative error code on failure.
Parameters
struct drm_panel *panel
- DRM panel
Description
This will typically turn off the panel’s backlight or disable the display drivers. For smart panels it should still be possible to communicate with the integrated circuitry via any command bus after this call.
Return
0 on success or a negative error code on failure.
-
int
drm_panel_get_modes
(struct drm_panel *panel, struct drm_connector *connector)¶ probe the available display modes of a panel
Parameters
struct drm_panel *panel
- DRM panel
struct drm_connector *connector
- DRM connector
Description
The modes probed from the panel are automatically added to the connector that the panel is attached to.
Return
The number of modes available from the panel on success or a negative error code on failure.
-
struct drm_panel *
of_drm_find_panel
(const struct device_node *np)¶ look up a panel using a device tree node
Parameters
const struct device_node *np
- device tree node of the panel
Description
Searches the set of registered panels for one that matches the given device tree node. If a matching panel is found, return a pointer to it.
Possible error codes returned by this function:
- EPROBE_DEFER: the panel device has not been probed yet, and the caller should retry later
- ENODEV: the device is not available (status != “okay” or “ok”)
Return
A pointer to the panel registered for the specified device tree node or an ERR_PTR() if no panel matching the device tree node can be found.
-
int
of_drm_get_panel_orientation
(const struct device_node *np, enum drm_panel_orientation *orientation)¶ look up the orientation of the panel through the “rotation” binding from a device tree node
Parameters
const struct device_node *np
- device tree node of the panel
enum drm_panel_orientation *orientation
- orientation enum to be filled in
Description
Looks up the rotation of a panel in the device tree. The orientation of the panel is expressed as a property name “rotation” in the device tree. The rotation in the device tree is counter clockwise.
Return
0 when a valid rotation value (0, 90, 180, or 270) is read or the rotation property doesn’t exist. Return a negative error code on failure.
Parameters
struct drm_panel *panel
- DRM panel
Description
Use this function to enable backlight handling if your panel uses device tree and has a backlight phandle.
When the panel is enabled backlight will be enabled after a
successful call to drm_panel_funcs.enable()
When the panel is disabled backlight will be disabled before the
call to drm_panel_funcs.disable()
.
A typical implementation for a panel driver supporting device tree
will call this function at probe time. Backlight will then be handled
transparently without requiring any intervention from the driver.
drm_panel_of_backlight()
must be called after the call to drm_panel_init()
.
Return
0 on success or a negative error code on failure.
-
int
drm_get_panel_orientation_quirk
(int width, int height)¶ Check for panel orientation quirks
Parameters
int width
- width in pixels of the panel
int height
- height in pixels of the panel
Description
This function checks for platform specific (e.g. DMI based) quirks providing info on panel_orientation for systems where this cannot be probed from the hard-/firm-ware. To avoid false-positive this function takes the panel resolution as argument and checks that against the resolution expected by the quirk-table entry.
Note this function is also used outside of the drm-subsys, by for example the efifb code. Because of this this function gets compiled into its own kernel-module when built as a module.
Return
A DRM_MODE_PANEL_ORIENTATION_* value if there is a quirk for this system, or DRM_MODE_PANEL_ORIENTATION_UNKNOWN if there is no quirk.
Panel Self Refresh Helper Reference¶
This helper library provides an easy way for drivers to leverage the atomic
framework to implement panel self refresh (SR) support. Drivers are
responsible for initializing and cleaning up the SR helpers on load/unload
(see drm_self_refresh_helper_init
/drm_self_refresh_helper_cleanup
).
The connector is responsible for setting
drm_connector_state.self_refresh_aware
to true at runtime if it is SR-aware
(meaning it knows how to initiate self refresh on the panel).
Once a crtc has enabled SR using drm_self_refresh_helper_init
, the
helpers will monitor activity and call back into the driver to enable/disable
SR as appropriate. The best way to think about this is that it’s a DPMS
on/off request with drm_crtc_state.self_refresh_active
set in crtc state
that tells you to disable/enable SR on the panel instead of power-cycling it.
During SR, drivers may choose to fully disable their crtc/encoder/bridge
hardware (in which case no driver changes are necessary), or they can inspect
drm_crtc_state.self_refresh_active
if they want to enter low power mode
without full disable (in case full disable/enable is too slow).
SR will be deactivated if there are any atomic updates affecting the pipe that is in SR mode. If a crtc is driving multiple connectors, all connectors must be SR aware and all will enter/exit SR mode at the same time.
If the crtc and connector are SR aware, but the panel connected does not
support it (or is otherwise unable to enter SR), the driver should fail
atomic_check when drm_crtc_state.self_refresh_active
is true.
-
void
drm_self_refresh_helper_update_avg_times
(struct drm_atomic_state *state, unsigned int commit_time_ms, unsigned int new_self_refresh_mask)¶ Updates a crtc’s SR time averages
Parameters
struct drm_atomic_state *state
- the state which has just been applied to hardware
unsigned int commit_time_ms
- the amount of time in ms that this commit took to complete
unsigned int new_self_refresh_mask
- bitmask of crtc’s that have self_refresh_active in new state
Description
Called after drm_mode_config_funcs.atomic_commit_tail
, this function will
update the average entry/exit self refresh times on self refresh transitions.
These averages will be used when calculating how long to delay before
entering self refresh mode after activity.
-
void
drm_self_refresh_helper_alter_state
(struct drm_atomic_state *state)¶ Alters the atomic state for SR exit
Parameters
struct drm_atomic_state *state
- the state currently being checked
Description
Called at the end of atomic check. This function checks the state for flags incompatible with self refresh exit and changes them. This is a bit disingenuous since userspace is expecting one thing and we’re giving it another. However in order to keep self refresh entirely hidden from userspace, this is required.
At the end, we queue up the self refresh entry work so we can enter PSR after the desired delay.
-
int
drm_self_refresh_helper_init
(struct drm_crtc *crtc)¶ Initializes self refresh helpers for a crtc
Parameters
struct drm_crtc *crtc
- the crtc which supports self refresh supported displays
Description
Returns zero if successful or -errno on failure
-
void
drm_self_refresh_helper_cleanup
(struct drm_crtc *crtc)¶ Cleans up self refresh helpers for a crtc
Parameters
struct drm_crtc *crtc
- the crtc to cleanup
HDCP Helper Functions Reference¶
-
int
drm_hdcp_check_ksvs_revoked
(struct drm_device *drm_dev, u8 *ksvs, u32 ksv_count)¶ Check the revoked status of the IDs
Parameters
struct drm_device *drm_dev
- drm_device for which HDCP revocation check is requested
u8 *ksvs
- List of KSVs (HDCP receiver IDs)
u32 ksv_count
- KSV count passed in through ksvs
Description
This function reads the HDCP System renewability Message(SRM Table) from userspace as a firmware and parses it for the revoked HDCP KSVs(Receiver IDs) detected by DCP LLC. Once the revoked KSVs are known, revoked state of the KSVs in the list passed in by display drivers are decided and response is sent.
SRM should be presented in the name of “display_hdcp_srm.bin”.
Format of the SRM table, that userspace needs to write into the binary file, is defined at: 1. Renewability chapter on 55th page of HDCP 1.4 specification https://www.digital-cp.com/sites/default/files/specifications/HDCP``20Specification````20Rev1_4_Secure``.pdf 2. Renewability chapter on 63rd page of HDCP 2.2 specification https://www.digital-cp.com/sites/default/files/specifications/HDCP``20on````20HDMI````20Specification````20Rev2_2_Final1``.pdf
Return
Count of the revoked KSVs or -ve error number incase of the failure.
-
int
drm_connector_attach_content_protection_property
(struct drm_connector *connector, bool hdcp_content_type)¶ attach content protection property
Parameters
struct drm_connector *connector
- connector to attach CP property on.
bool hdcp_content_type
- is HDCP Content Type property needed for connector
Description
This is used to add support for content protection on select connectors. Content Protection is intentionally vague to allow for different underlying technologies, however it is most implemented by HDCP.
When hdcp_content_type is true enum property called HDCP Content Type is created (if it is not already) and attached to the connector.
This property is used for sending the protected content’s stream type from userspace to kernel on selected connectors. Protected content provider will decide their type of their content and declare the same to kernel.
Content type will be used during the HDCP 2.2 authentication.
Content type will be set to drm_connector_state.hdcp_content_type
.
The content protection will be set to drm_connector_state.content_protection
When kernel triggered content protection state change like DESIRED->ENABLED
and ENABLED->DESIRED, will use drm_hdcp_update_content_protection()
to update
the content protection state of a connector.
Return
Zero on success, negative errno on failure.
-
void
drm_hdcp_update_content_protection
(struct drm_connector *connector, u64 val)¶ Updates the content protection state of a connector
Parameters
struct drm_connector *connector
- drm_connector on which content protection state needs an update
u64 val
- New state of the content protection property
Description
This function can be used by display drivers, to update the kernel triggered content protection state changes of a drm_connector such as DESIRED->ENABLED and ENABLED->DESIRED. No uevent for DESIRED->UNDESIRED or ENABLED->UNDESIRED, as userspace is triggering such state change and kernel performs it without fail.This function update the new state of the property into the connector’s state and generate an uevent to notify the userspace.
Display Port Helper Functions Reference¶
These functions contain some common logic and helpers at various abstraction levels to deal with Display Port sink devices and related things like DP aux channel transfers, EDID reading over DP aux channels, decoding certain DPCD blocks, …
The DisplayPort AUX channel is an abstraction to allow generic, driver- independent access to AUX functionality. Drivers can take advantage of this by filling in the fields of the drm_dp_aux structure.
Transactions are described using a hardware-independent drm_dp_aux_msg structure, which is passed into a driver’s .transfer() implementation. Both native and I2C-over-AUX transactions are supported.
-
struct
dp_sdp_header
¶ DP secondary data packet header
Definition
struct dp_sdp_header {
u8 HB0;
u8 HB1;
u8 HB2;
u8 HB3;
};
Members
HB0
- Secondary Data Packet ID
HB1
- Secondary Data Packet Type
HB2
- Secondary Data Packet Specific header, Byte 0
HB3
- Secondary Data packet Specific header, Byte 1
-
struct
dp_sdp
¶ DP secondary data packet
Definition
struct dp_sdp {
struct dp_sdp_header sdp_header;
u8 db[32];
};
Members
sdp_header
- DP secondary data packet header
db
- DP secondaray data packet data blocks VSC SDP Payload for PSR db[0]: Stereo Interface db[1]: 0 - PSR State; 1 - Update RFB; 2 - CRC Valid db[2]: CRC value bits 7:0 of the R or Cr component db[3]: CRC value bits 15:8 of the R or Cr component db[4]: CRC value bits 7:0 of the G or Y component db[5]: CRC value bits 15:8 of the G or Y component db[6]: CRC value bits 7:0 of the B or Cb component db[7]: CRC value bits 15:8 of the B or Cb component db[8] - db[31]: Reserved VSC SDP Payload for Pixel Encoding/Colorimetry Format db[0] - db[15]: Reserved db[16]: Pixel Encoding and Colorimetry Formats db[17]: Dynamic Range and Component Bit Depth db[18]: Content Type db[19] - db[31]: Reserved
-
enum
dp_pixelformat
¶ drm DP Pixel encoding formats
Constants
DP_PIXELFORMAT_RGB
- RGB pixel encoding format
DP_PIXELFORMAT_YUV444
- YCbCr 4:4:4 pixel encoding format
DP_PIXELFORMAT_YUV422
- YCbCr 4:2:2 pixel encoding format
DP_PIXELFORMAT_YUV420
- YCbCr 4:2:0 pixel encoding format
DP_PIXELFORMAT_Y_ONLY
- Y Only pixel encoding format
DP_PIXELFORMAT_RAW
- RAW pixel encoding format
DP_PIXELFORMAT_RESERVED
- Reserved pixel encoding format
Description
This enum is used to indicate DP VSC SDP Pixel encoding formats. It is based on DP 1.4 spec [Table 2-117: VSC SDP Payload for DB16 through DB18]
-
enum
dp_colorimetry
¶ drm DP Colorimetry formats
Constants
DP_COLORIMETRY_DEFAULT
- sRGB (IEC 61966-2-1) or ITU-R BT.601 colorimetry format
DP_COLORIMETRY_RGB_WIDE_FIXED
- RGB wide gamut fixed point colorimetry format
DP_COLORIMETRY_BT709_YCC
- ITU-R BT.709 colorimetry format
DP_COLORIMETRY_RGB_WIDE_FLOAT
- RGB wide gamut floating point (scRGB (IEC 61966-2-2)) colorimetry format
DP_COLORIMETRY_XVYCC_601
- xvYCC601 colorimetry format
DP_COLORIMETRY_OPRGB
- OpRGB colorimetry format
DP_COLORIMETRY_XVYCC_709
- xvYCC709 colorimetry format
DP_COLORIMETRY_DCI_P3_RGB
- DCI-P3 (SMPTE RP 431-2) colorimetry format
DP_COLORIMETRY_SYCC_601
- sYCC601 colorimetry format
DP_COLORIMETRY_RGB_CUSTOM
- RGB Custom Color Profile colorimetry format
DP_COLORIMETRY_OPYCC_601
- opYCC601 colorimetry format
DP_COLORIMETRY_BT2020_RGB
- ITU-R BT.2020 R’ G’ B’ colorimetry format
DP_COLORIMETRY_BT2020_CYCC
- ITU-R BT.2020 Y’c C’bc C’rc colorimetry format
DP_COLORIMETRY_BT2020_YCC
- ITU-R BT.2020 Y’ C’b C’r colorimetry format
Description
This enum is used to indicate DP VSC SDP Colorimetry formats. It is based on DP 1.4 spec [Table 2-117: VSC SDP Payload for DB16 through DB18] and a name of enum member follows DRM_MODE_COLORIMETRY definition.
-
enum
dp_dynamic_range
¶ drm DP Dynamic Range
Constants
DP_DYNAMIC_RANGE_VESA
- VESA range
DP_DYNAMIC_RANGE_CTA
- CTA range
Description
This enum is used to indicate DP VSC SDP Dynamic Range. It is based on DP 1.4 spec [Table 2-117: VSC SDP Payload for DB16 through DB18]
-
enum
dp_content_type
¶ drm DP Content Type
Constants
DP_CONTENT_TYPE_NOT_DEFINED
- Not defined type
DP_CONTENT_TYPE_GRAPHICS
- Graphics type
DP_CONTENT_TYPE_PHOTO
- Photo type
DP_CONTENT_TYPE_VIDEO
- Video type
DP_CONTENT_TYPE_GAME
- Game type
Description
This enum is used to indicate DP VSC SDP Content Types. It is based on DP 1.4 spec [Table 2-117: VSC SDP Payload for DB16 through DB18] CTA-861-G defines content types and expected processing by a sink device
-
struct
drm_dp_vsc_sdp
¶ drm DP VSC SDP
Definition
struct drm_dp_vsc_sdp {
unsigned char sdp_type;
unsigned char revision;
unsigned char length;
enum dp_pixelformat pixelformat;
enum dp_colorimetry colorimetry;
int bpc;
enum dp_dynamic_range dynamic_range;
enum dp_content_type content_type;
};
Members
sdp_type
- secondary-data packet type
revision
- revision number
length
- number of valid data bytes
pixelformat
- pixel encoding format
colorimetry
- colorimetry format
bpc
- bit per color
dynamic_range
- dynamic range information
content_type
- CTA-861-G defines content types and expected processing by a sink device
Description
This structure represents a DP VSC SDP of drm It is based on DP 1.4 spec [Table 2-116: VSC SDP Header Bytes] and [Table 2-117: VSC SDP Payload for DB16 through DB18]
-
struct
drm_dp_aux_msg
¶ DisplayPort AUX channel transaction
Definition
struct drm_dp_aux_msg {
unsigned int address;
u8 request;
u8 reply;
void *buffer;
size_t size;
};
Members
address
- address of the (first) register to access
request
- contains the type of transaction (see DP_AUX_* macros)
reply
- upon completion, contains the reply type of the transaction
buffer
- pointer to a transmission or reception buffer
size
- size of buffer
-
struct
drm_dp_aux_cec
¶ DisplayPort CEC-Tunneling-over-AUX
Definition
struct drm_dp_aux_cec {
struct mutex lock;
struct cec_adapter *adap;
struct drm_connector *connector;
struct delayed_work unregister_work;
};
Members
lock
- mutex protecting this struct
adap
- the CEC adapter for CEC-Tunneling-over-AUX support.
connector
- the connector this CEC adapter is associated with
unregister_work
- unregister the CEC adapter
-
struct
drm_dp_aux
¶ DisplayPort AUX channel
Definition
struct drm_dp_aux {
const char *name;
struct i2c_adapter ddc;
struct device *dev;
struct drm_crtc *crtc;
struct mutex hw_mutex;
struct work_struct crc_work;
u8 crc_count;
ssize_t (*transfer)(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg);
unsigned i2c_nack_count;
unsigned i2c_defer_count;
struct drm_dp_aux_cec cec;
bool is_remote;
};
Members
name
- user-visible name of this AUX channel and the I2C-over-AUX adapter
ddc
- I2C adapter that can be used for I2C-over-AUX communication
dev
- pointer to
struct device
that is the parent for this AUX channel crtc
- backpointer to the crtc that is currently using this AUX channel
hw_mutex
- internal mutex used for locking transfers
crc_work
- worker that captures CRCs for each frame
crc_count
- counter of captured frame CRCs
transfer
- transfers a message representing a single AUX transaction
i2c_nack_count
- Counts I2C NACKs, used for DP validation.
i2c_defer_count
- Counts I2C DEFERs, used for DP validation.
cec
- struct containing fields used for CEC-Tunneling-over-AUX.
is_remote
- Is this AUX CH actually using sideband messaging.
Description
The .dev field should be set to a pointer to the device that implements the AUX channel.
The .name field may be used to specify the name of the I2C adapter. If set to NULL, dev_name() of .dev will be used.
Drivers provide a hardware-specific implementation of how transactions are executed via the .transfer() function. A pointer to a drm_dp_aux_msg structure describing the transaction is passed into this function. Upon success, the implementation should return the number of payload bytes that were transferred, or a negative error-code on failure. Helpers propagate errors from the .transfer() function, with the exception of the -EBUSY error, which causes a transaction to be retried. On a short, helpers will return -EPROTO to make it simpler to check for failure.
An AUX channel can also be used to transport I2C messages to a sink. A
typical application of that is to access an EDID that’s present in the
sink device. The .transfer() function can also be used to execute such
transactions. The drm_dp_aux_register()
function registers an I2C
adapter that can be passed to drm_probe_ddc()
. Upon removal, drivers
should call drm_dp_aux_unregister()
to remove the I2C adapter.
The I2C adapter uses long transfers by default; if a partial response is
received, the adapter will drop down to the size given by the partial
response for this transaction only.
Note that the aux helper code assumes that the .transfer() function only modifies the reply field of the drm_dp_aux_msg structure. The retry logic and i2c helpers assume this is the case.
-
ssize_t
drm_dp_dpcd_readb
(struct drm_dp_aux *aux, unsigned int offset, u8 *valuep)¶ read a single byte from the DPCD
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
unsigned int offset
- address of the register to read
u8 *valuep
- location where the value of the register will be stored
Description
Returns the number of bytes transferred (1) on success, or a negative error code on failure.
-
ssize_t
drm_dp_dpcd_writeb
(struct drm_dp_aux *aux, unsigned int offset, u8 value)¶ write a single byte to the DPCD
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
unsigned int offset
- address of the register to write
u8 value
- value to write to the register
Description
Returns the number of bytes transferred (1) on success, or a negative error code on failure.
-
struct
drm_dp_desc
¶ DP branch/sink device descriptor
Definition
struct drm_dp_desc {
struct drm_dp_dpcd_ident ident;
u32 quirks;
};
Members
ident
- DP device identification from DPCD 0x400 (sink) or 0x500 (branch).
quirks
- Quirks; use
drm_dp_has_quirk()
to query for the quirks.
-
enum
drm_dp_quirk
¶ Display Port sink/branch device specific quirks
Constants
DP_DPCD_QUIRK_CONSTANT_N
- The device requires main link attributes Mvid and Nvid to be limited to 16 bits. So will give a constant value (0x8000) for compatability.
DP_DPCD_QUIRK_NO_PSR
- The device does not support PSR even if reports that it supports or driver still need to implement proper handling for such device.
DP_DPCD_QUIRK_NO_SINK_COUNT
- The device does not set SINK_COUNT to a non-zero value.
The driver should ignore SINK_COUNT during detection. Note that
drm_dp_read_sink_count_cap()
automatically checks for this quirk. DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD
- The device supports MST DSC despite not supporting Virtual DPCD. The DSC caps can be read from the physical aux instead.
DP_QUIRK_FORCE_DPCD_BACKLIGHT
- The device is telling the truth when it says that it uses DPCD backlight controls, even if the system’s firmware disagrees. This quirk should be checked against both the ident and panel EDID. When present, the driver should honor the DPCD backlight capabilities advertised.
DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS
- The device supports a link rate of 3.24 Gbps (multiplier 0xc) despite the DP_MAX_LINK_RATE register reporting a lower max multiplier.
Description
Display Port sink and branch devices in the wild have a variety of bugs, try
to collect them here. The quirks are shared, but it’s up to the drivers to
implement workarounds for them. Note that because some devices have
unreliable OUIDs, the EDID of sinks should also be checked for quirks using
drm_dp_get_edid_quirks()
.
-
bool
drm_dp_has_quirk
(const struct drm_dp_desc *desc, u32 edid_quirks, enum drm_dp_quirk quirk)¶ does the DP device have a specific quirk
Parameters
const struct drm_dp_desc *desc
- Device descriptor filled by
drm_dp_read_desc()
u32 edid_quirks
- Optional quirk bitmask filled by
drm_dp_get_edid_quirks()
enum drm_dp_quirk quirk
- Quirk to query for
Description
Return true if DP device identified by desc has quirk.
-
struct
drm_dp_phy_test_params
¶ DP Phy Compliance parameters
Definition
struct drm_dp_phy_test_params {
int link_rate;
u8 num_lanes;
u8 phy_pattern;
u8 hbr2_reset[2];
u8 custom80[10];
bool enhanced_frame_cap;
};
Members
link_rate
- Requested Link rate from DPCD 0x219
num_lanes
- Number of lanes requested by sing through DPCD 0x220
phy_pattern
- DP Phy test pattern from DPCD 0x248
hbr2_reset
- DP HBR2_COMPLIANCE_SCRAMBLER_RESET from DCPD 0x24A and 0x24B
custom80
- DP Test_80BIT_CUSTOM_PATTERN from DPCDs 0x250 through 0x259
enhanced_frame_cap
- flag for enhanced frame capability.
-
ssize_t
drm_dp_dpcd_read
(struct drm_dp_aux *aux, unsigned int offset, void *buffer, size_t size)¶ read a series of bytes from the DPCD
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel (SST or MST)
unsigned int offset
- address of the (first) register to read
void *buffer
- buffer to store the register values
size_t size
- number of bytes in buffer
Description
Returns the number of bytes transferred on success, or a negative error code on failure. -EIO is returned if the request was NAKed by the sink or if the retry count was exceeded. If not all bytes were transferred, this function returns -EPROTO. Errors from the underlying AUX channel transfer function, with the exception of -EBUSY (which causes the transaction to be retried), are propagated to the caller.
-
ssize_t
drm_dp_dpcd_write
(struct drm_dp_aux *aux, unsigned int offset, void *buffer, size_t size)¶ write a series of bytes to the DPCD
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel (SST or MST)
unsigned int offset
- address of the (first) register to write
void *buffer
- buffer containing the values to write
size_t size
- number of bytes in buffer
Description
Returns the number of bytes transferred on success, or a negative error code on failure. -EIO is returned if the request was NAKed by the sink or if the retry count was exceeded. If not all bytes were transferred, this function returns -EPROTO. Errors from the underlying AUX channel transfer function, with the exception of -EBUSY (which causes the transaction to be retried), are propagated to the caller.
-
int
drm_dp_dpcd_read_link_status
(struct drm_dp_aux *aux, u8 status[DP_LINK_STATUS_SIZE])¶ read DPCD link status (bytes 0x202-0x207)
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
u8 status[DP_LINK_STATUS_SIZE]
- buffer to store the link status in (must be at least 6 bytes)
Description
Returns the number of bytes transferred on success or a negative error code on failure.
-
int
drm_dp_dpcd_read_phy_link_status
(struct drm_dp_aux *aux, enum drm_dp_phy dp_phy, u8 link_status[DP_LINK_STATUS_SIZE])¶ get the link status information for a DP PHY
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
enum drm_dp_phy dp_phy
- the DP PHY to get the link status for
u8 link_status[DP_LINK_STATUS_SIZE]
- buffer to return the status in
Description
Fetch the AUX DPCD registers for the DPRX or an LTTPR PHY link status. The layout of the returned link_status matches the DPCD register layout of the DPRX PHY link status.
Returns 0 if the information was read successfully or a negative error code on failure.
-
bool
drm_dp_downstream_is_type
(const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4], u8 type)¶ is the downstream facing port of certain type?
Parameters
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- DisplayPort configuration data
const u8 port_cap[4]
- port capabilities
u8 type
- port type to be checked. Can be:
DP_DS_PORT_TYPE_DP
,DP_DS_PORT_TYPE_VGA
,DP_DS_PORT_TYPE_DVI
,DP_DS_PORT_TYPE_HDMI
,DP_DS_PORT_TYPE_NON_EDID
,DP_DS_PORT_TYPE_DP_DUALMODE
orDP_DS_PORT_TYPE_WIRELESS
.
Description
Caveat: Only works with DPCD 1.1+ port caps.
Return
whether the downstream facing port matches the type.
-
bool
drm_dp_downstream_is_tmds
(const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4], const struct edid *edid)¶ is the downstream facing port TMDS?
Parameters
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- DisplayPort configuration data
const u8 port_cap[4]
- port capabilities
const struct edid *edid
- EDID
Return
whether the downstream facing port is TMDS (HDMI/DVI).
-
bool
drm_dp_send_real_edid_checksum
(struct drm_dp_aux *aux, u8 real_edid_checksum)¶ send back real edid checksum value
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
u8 real_edid_checksum
- real edid checksum for the last block
Return
True on success
-
int
drm_dp_read_dpcd_caps
(struct drm_dp_aux *aux, u8 dpcd[DP_RECEIVER_CAP_SIZE])¶ read DPCD caps and extended DPCD caps if available
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
u8 dpcd[DP_RECEIVER_CAP_SIZE]
- Buffer to store the resulting DPCD in
Description
Attempts to read the base DPCD caps for aux. Additionally, this function
checks for and reads the extended DPRX caps (DP_DP13_DPCD_REV
) if
present.
Return
0
if the DPCD was read successfully, negative error code
otherwise.
-
int
drm_dp_read_downstream_info
(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIVER_CAP_SIZE], u8 downstream_ports[DP_MAX_DOWNSTREAM_PORTS])¶ read DPCD downstream port info if available
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- A cached copy of the port’s DPCD
u8 downstream_ports[DP_MAX_DOWNSTREAM_PORTS]
- buffer to store the downstream port info in
Description
See also:
drm_dp_downstream_max_clock()
drm_dp_downstream_max_bpc()
Return
0 if either the downstream port info was read successfully or there was no downstream info to read, or a negative error code otherwise.
-
int
drm_dp_downstream_max_dotclock
(const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4])¶ extract downstream facing port max dot clock
Parameters
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- DisplayPort configuration data
const u8 port_cap[4]
- port capabilities
Return
Downstream facing port max dot clock in kHz on success, or 0 if max clock not defined
-
int
drm_dp_downstream_max_tmds_clock
(const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4], const struct edid *edid)¶ extract downstream facing port max TMDS clock
Parameters
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- DisplayPort configuration data
const u8 port_cap[4]
- port capabilities
const struct edid *edid
- EDID
Return
HDMI/DVI downstream facing port max TMDS clock in kHz on success, or 0 if max TMDS clock not defined
-
int
drm_dp_downstream_min_tmds_clock
(const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4], const struct edid *edid)¶ extract downstream facing port min TMDS clock
Parameters
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- DisplayPort configuration data
const u8 port_cap[4]
- port capabilities
const struct edid *edid
- EDID
Return
HDMI/DVI downstream facing port min TMDS clock in kHz on success, or 0 if max TMDS clock not defined
-
int
drm_dp_downstream_max_bpc
(const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4], const struct edid *edid)¶ extract downstream facing port max bits per component
Parameters
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- DisplayPort configuration data
const u8 port_cap[4]
- downstream facing port capabilities
const struct edid *edid
- EDID
Return
Max bpc on success or 0 if max bpc not defined
-
bool
drm_dp_downstream_420_passthrough
(const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4])¶ determine downstream facing port YCbCr 4:2:0 pass-through capability
Parameters
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- DisplayPort configuration data
const u8 port_cap[4]
- downstream facing port capabilities
Return
whether the downstream facing port can pass through YCbCr 4:2:0
-
bool
drm_dp_downstream_444_to_420_conversion
(const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4])¶ determine downstream facing port YCbCr 4:4:4->4:2:0 conversion capability
Parameters
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- DisplayPort configuration data
const u8 port_cap[4]
- downstream facing port capabilities
Return
whether the downstream facing port can convert YCbCr 4:4:4 to 4:2:0
-
struct drm_display_mode *
drm_dp_downstream_mode
(struct drm_device *dev, const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4])¶ return a mode for downstream facing port
Parameters
struct drm_device *dev
- DRM device
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- DisplayPort configuration data
const u8 port_cap[4]
- port capabilities
Description
Provides a suitable mode for downstream facing ports without EDID.
Return
A new drm_display_mode on success or NULL on failure
-
int
drm_dp_downstream_id
(struct drm_dp_aux *aux, char id[6])¶ identify branch device
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
char id[6]
- DisplayPort branch device id
Description
Returns branch device id on success or NULL on failure
-
void
drm_dp_downstream_debug
(struct seq_file *m, const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4], const struct edid *edid, struct drm_dp_aux *aux)¶ debug DP branch devices
Parameters
struct seq_file *m
- pointer for debugfs file
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- DisplayPort configuration data
const u8 port_cap[4]
- port capabilities
const struct edid *edid
- EDID
struct drm_dp_aux *aux
- DisplayPort AUX channel
-
enum drm_mode_subconnector
drm_dp_subconnector_type
(const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4])¶ get DP branch device type
Parameters
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- DisplayPort configuration data
const u8 port_cap[4]
- port capabilities
-
void
drm_dp_set_subconnector_property
(struct drm_connector *connector, enum drm_connector_status status, const u8 *dpcd, const u8 port_cap[4])¶ set subconnector for DP connector
Parameters
struct drm_connector *connector
- connector to set property on
enum drm_connector_status status
- connector status
const u8 *dpcd
- DisplayPort configuration data
const u8 port_cap[4]
- port capabilities
Description
Called by a driver on every detect event.
-
bool
drm_dp_read_sink_count_cap
(struct drm_connector *connector, const u8 dpcd[DP_RECEIVER_CAP_SIZE], const struct drm_dp_desc *desc)¶ Check whether a given connector has a valid sink count
Parameters
struct drm_connector *connector
- The DRM connector to check
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- A cached copy of the connector’s DPCD RX capabilities
const struct drm_dp_desc *desc
- A cached copy of the connector’s DP descriptor
Description
See also: drm_dp_read_sink_count()
Return
True
if the (e)DP connector has a valid sink count that should
be probed, false
otherwise.
-
int
drm_dp_read_sink_count
(struct drm_dp_aux *aux)¶ Retrieve the sink count for a given sink
Parameters
struct drm_dp_aux *aux
- The DP AUX channel to use
Description
See also: drm_dp_read_sink_count_cap()
Return
The current sink count reported by aux, or a negative error code otherwise.
-
void
drm_dp_remote_aux_init
(struct drm_dp_aux *aux)¶ minimally initialise a remote aux channel
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
Description
Used for remote aux channel in general. Merely initialize the crc work struct.
-
void
drm_dp_aux_init
(struct drm_dp_aux *aux)¶ minimally initialise an aux channel
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
Description
If you need to use the drm_dp_aux’s i2c adapter prior to registering it
with the outside world, call drm_dp_aux_init()
first. You must still
call drm_dp_aux_register()
once the connector has been registered to
allow userspace access to the auxiliary DP channel.
-
int
drm_dp_aux_register
(struct drm_dp_aux *aux)¶ initialise and register aux channel
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
Description
Automatically calls drm_dp_aux_init()
if this hasn’t been done yet.
This should only be called when the underlying struct drm_connector
is
initialiazed already. Therefore the best place to call this is from
drm_connector_funcs.late_register
. Not that drivers which don’t follow this
will Oops when CONFIG_DRM_DP_AUX_CHARDEV is enabled.
Drivers which need to use the aux channel before that point (e.g. at driver
load time, before drm_dev_register()
has been called) need to call
drm_dp_aux_init()
.
Returns 0 on success or a negative error code on failure.
-
void
drm_dp_aux_unregister
(struct drm_dp_aux *aux)¶ unregister an AUX adapter
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
-
int
drm_dp_psr_setup_time
(const u8 psr_cap[EDP_PSR_RECEIVER_CAP_SIZE])¶ PSR setup in time usec
Parameters
const u8 psr_cap[EDP_PSR_RECEIVER_CAP_SIZE]
- PSR capabilities from DPCD
Return
PSR setup time for the panel in microseconds, negative error code on failure.
-
int
drm_dp_start_crc
(struct drm_dp_aux *aux, struct drm_crtc *crtc)¶ start capture of frame CRCs
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
struct drm_crtc *crtc
- CRTC displaying the frames whose CRCs are to be captured
Description
Returns 0 on success or a negative error code on failure.
-
int
drm_dp_stop_crc
(struct drm_dp_aux *aux)¶ stop capture of frame CRCs
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
Description
Returns 0 on success or a negative error code on failure.
-
u32
drm_dp_get_edid_quirks
(const struct edid *edid)¶ Check the EDID of a DP device to find additional DP-specific quirks
Parameters
const struct edid *edid
- The EDID to check
Description
While OUIDs are meant to be used to recognize a DisplayPort device, a lot
of manufacturers don’t seem to like following standards and neglect to fill
the dev-ID in, making it impossible to only use OUIDs for determining
quirks in some cases. This function can be used to check the EDID and look
up any additional DP quirks. The bits returned by this function correspond
to the quirk bits in drm_dp_quirk
.
Return
a bitmask of quirks, if any. The driver can check this using
drm_dp_has_quirk()
.
-
int
drm_dp_read_desc
(struct drm_dp_aux *aux, struct drm_dp_desc *desc, bool is_branch)¶ read sink/branch descriptor from DPCD
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
struct drm_dp_desc *desc
- Device descriptor to fill from DPCD
bool is_branch
- true for branch devices, false for sink devices
Description
Read DPCD 0x400 (sink) or 0x500 (branch) into desc. Also debug log the identification.
Returns 0 on success or a negative error code on failure.
-
u8
drm_dp_dsc_sink_max_slice_count
(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE], bool is_edp)¶ Get the max slice count supported by the DSC sink.
Parameters
const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]
- DSC capabilities from DPCD
bool is_edp
- true if its eDP, false for DP
Description
Read the slice capabilities DPCD register from DSC sink to get
the maximum slice count supported. This is used to populate
the DSC parameters in the struct drm_dsc_config
by the driver.
Driver creates an infoframe using these parameters to populate
struct drm_dsc_pps_infoframe
. These are sent to the sink using DSC
infoframe using the helper function drm_dsc_pps_infoframe_pack()
Return
Maximum slice count supported by DSC sink or 0 its invalid
-
u8
drm_dp_dsc_sink_line_buf_depth
(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])¶ Get the line buffer depth in bits
Parameters
const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]
- DSC capabilities from DPCD
Description
Read the DSC DPCD register to parse the line buffer depth in bits which is
number of bits of precision within the decoder line buffer supported by
the DSC sink. This is used to populate the DSC parameters in the
struct drm_dsc_config
by the driver.
Driver creates an infoframe using these parameters to populate
struct drm_dsc_pps_infoframe
. These are sent to the sink using DSC
infoframe using the helper function drm_dsc_pps_infoframe_pack()
Return
Line buffer depth supported by DSC panel or 0 its invalid
-
int
drm_dp_dsc_sink_supported_input_bpcs
(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE], u8 dsc_bpc[3])¶ Get all the input bits per component values supported by the DSC sink.
Parameters
const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]
- DSC capabilities from DPCD
u8 dsc_bpc[3]
- An array to be filled by this helper with supported input bpcs.
Description
Read the DSC DPCD from the sink device to parse the supported bits per
component values. This is used to populate the DSC parameters
in the struct drm_dsc_config
by the driver.
Driver creates an infoframe using these parameters to populate
struct drm_dsc_pps_infoframe
. These are sent to the sink using DSC
infoframe using the helper function drm_dsc_pps_infoframe_pack()
Return
Number of input BPC values parsed from the DPCD
-
int
drm_dp_read_lttpr_common_caps
(struct drm_dp_aux *aux, u8 caps[DP_LTTPR_COMMON_CAP_SIZE])¶ read the LTTPR common capabilities
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
u8 caps[DP_LTTPR_COMMON_CAP_SIZE]
- buffer to return the capability info in
Description
Read capabilities common to all LTTPRs.
Returns 0 on success or a negative error code on failure.
-
int
drm_dp_read_lttpr_phy_caps
(struct drm_dp_aux *aux, enum drm_dp_phy dp_phy, u8 caps[DP_LTTPR_PHY_CAP_SIZE])¶ read the capabilities for a given LTTPR PHY
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
enum drm_dp_phy dp_phy
- LTTPR PHY to read the capabilities for
u8 caps[DP_LTTPR_PHY_CAP_SIZE]
- buffer to return the capability info in
Description
Read the capabilities for the given LTTPR PHY.
Returns 0 on success or a negative error code on failure.
-
int
drm_dp_lttpr_count
(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE])¶ get the number of detected LTTPRs
Parameters
const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]
- LTTPR common capabilities
Description
Get the number of detected LTTPRs from the LTTPR common capabilities info.
Return
-ERANGE if more than supported number (8) of LTTPRs are detected -EINVAL if the DP_PHY_REPEATER_CNT register contains an invalid value otherwise the number of detected LTTPRs
-
int
drm_dp_lttpr_max_link_rate
(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE])¶ get the maximum link rate supported by all LTTPRs
Parameters
const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]
- LTTPR common capabilities
Description
Returns the maximum link rate supported by all detected LTTPRs.
-
int
drm_dp_lttpr_max_lane_count
(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE])¶ get the maximum lane count supported by all LTTPRs
Parameters
const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]
- LTTPR common capabilities
Description
Returns the maximum lane count supported by all detected LTTPRs.
-
bool
drm_dp_lttpr_voltage_swing_level_3_supported
(const u8 caps[DP_LTTPR_PHY_CAP_SIZE])¶ check for LTTPR vswing3 support
Parameters
const u8 caps[DP_LTTPR_PHY_CAP_SIZE]
- LTTPR PHY capabilities
Description
Returns true if the caps for an LTTPR TX PHY indicate support for voltage swing level 3.
-
bool
drm_dp_lttpr_pre_emphasis_level_3_supported
(const u8 caps[DP_LTTPR_PHY_CAP_SIZE])¶ check for LTTPR preemph3 support
Parameters
const u8 caps[DP_LTTPR_PHY_CAP_SIZE]
- LTTPR PHY capabilities
Description
Returns true if the caps for an LTTPR TX PHY indicate support for pre-emphasis level 3.
-
int
drm_dp_get_phy_test_pattern
(struct drm_dp_aux *aux, struct drm_dp_phy_test_params *data)¶ get the requested pattern from the sink.
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
struct drm_dp_phy_test_params *data
- DP phy compliance test parameters.
Description
Returns 0 on success or a negative error code on failure.
-
int
drm_dp_set_phy_test_pattern
(struct drm_dp_aux *aux, struct drm_dp_phy_test_params *data, u8 dp_rev)¶ set the pattern to the sink.
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
struct drm_dp_phy_test_params *data
- DP phy compliance test parameters.
u8 dp_rev
- DP revision to use for compliance testing
Description
Returns 0 on success or a negative error code on failure.
Display Port CEC Helper Functions Reference¶
These functions take care of supporting the CEC-Tunneling-over-AUX feature of DisplayPort-to-HDMI adapters.
-
void
drm_dp_cec_irq
(struct drm_dp_aux *aux)¶ handle CEC interrupt, if any
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
Description
Should be called when handling an IRQ_HPD request. If CEC-tunneling-over-AUX is present, then it will check for a CEC_IRQ and handle it accordingly.
-
void
drm_dp_cec_register_connector
(struct drm_dp_aux *aux, struct drm_connector *connector)¶ register a new connector
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
struct drm_connector *connector
- drm connector
Description
A new connector was registered with associated CEC adapter name and CEC adapter parent device. After registering the name and parent drm_dp_cec_set_edid() is called to check if the connector supports CEC and to register a CEC adapter if that is the case.
-
void
drm_dp_cec_unregister_connector
(struct drm_dp_aux *aux)¶ unregister the CEC adapter, if any
Parameters
struct drm_dp_aux *aux
- DisplayPort AUX channel
Display Port Dual Mode Adaptor Helper Functions Reference¶
Helper functions to deal with DP dual mode (aka. DP++) adaptors.
Type 1: Adaptor registers (if any) and the sink DDC bus may be accessed via I2C.
Type 2: Adaptor registers and sink DDC bus can be accessed either via I2C or I2C-over-AUX. Source devices may choose to implement either of these access methods.
-
enum
drm_lspcon_mode
¶
Constants
DRM_LSPCON_MODE_INVALID
- No LSPCON.
DRM_LSPCON_MODE_LS
- Level shifter mode of LSPCON which drives DP++ to HDMI 1.4 conversion.
DRM_LSPCON_MODE_PCON
- Protocol converter mode of LSPCON which drives DP++ to HDMI 2.0 active conversion.
-
enum
drm_dp_dual_mode_type
¶ Type of the DP dual mode adaptor
Constants
DRM_DP_DUAL_MODE_NONE
- No DP dual mode adaptor
DRM_DP_DUAL_MODE_UNKNOWN
- Could be either none or type 1 DVI adaptor
DRM_DP_DUAL_MODE_TYPE1_DVI
- Type 1 DVI adaptor
DRM_DP_DUAL_MODE_TYPE1_HDMI
- Type 1 HDMI adaptor
DRM_DP_DUAL_MODE_TYPE2_DVI
- Type 2 DVI adaptor
DRM_DP_DUAL_MODE_TYPE2_HDMI
- Type 2 HDMI adaptor
DRM_DP_DUAL_MODE_LSPCON
- Level shifter / protocol converter
-
ssize_t
drm_dp_dual_mode_read
(struct i2c_adapter *adapter, u8 offset, void *buffer, size_t size)¶ Read from the DP dual mode adaptor register(s)
Parameters
struct i2c_adapter *adapter
- I2C adapter for the DDC bus
u8 offset
- register offset
void *buffer
- buffer for return data
size_t size
- sizo of the buffer
Description
Reads size bytes from the DP dual mode adaptor registers starting at offset.
Return
0 on success, negative error code on failure
-
ssize_t
drm_dp_dual_mode_write
(struct i2c_adapter *adapter, u8 offset, const void *buffer, size_t size)¶ Write to the DP dual mode adaptor register(s)
Parameters
struct i2c_adapter *adapter
- I2C adapter for the DDC bus
u8 offset
- register offset
const void *buffer
- buffer for write data
size_t size
- sizo of the buffer
Description
Writes size bytes to the DP dual mode adaptor registers starting at offset.
Return
0 on success, negative error code on failure
-
enum drm_dp_dual_mode_type
drm_dp_dual_mode_detect
(struct i2c_adapter *adapter)¶ Identify the DP dual mode adaptor
Parameters
struct i2c_adapter *adapter
- I2C adapter for the DDC bus
Description
Attempt to identify the type of the DP dual mode adaptor used.
Note that when the answer is DRM_DP_DUAL_MODE_UNKNOWN it’s not certain whether we’re dealing with a native HDMI port or a type 1 DVI dual mode adaptor. The driver will have to use some other hardware/driver specific mechanism to make that distinction.
Return
The type of the DP dual mode adaptor used
-
int
drm_dp_dual_mode_max_tmds_clock
(enum drm_dp_dual_mode_type type, struct i2c_adapter *adapter)¶ Max TMDS clock for DP dual mode adaptor
Parameters
enum drm_dp_dual_mode_type type
- DP dual mode adaptor type
struct i2c_adapter *adapter
- I2C adapter for the DDC bus
Description
Determine the max TMDS clock the adaptor supports based on the
type of the dual mode adaptor and the DP_DUAL_MODE_MAX_TMDS_CLOCK
register (on type2 adaptors). As some type 1 adaptors have
problems with registers (see comments in drm_dp_dual_mode_detect()
)
we don’t read the register on those, instead we simply assume
a 165 MHz limit based on the specification.
Return
Maximum supported TMDS clock rate for the DP dual mode adaptor in kHz.
-
int
drm_dp_dual_mode_get_tmds_output
(enum drm_dp_dual_mode_type type, struct i2c_adapter *adapter, bool *enabled)¶ Get the state of the TMDS output buffers in the DP dual mode adaptor
Parameters
enum drm_dp_dual_mode_type type
- DP dual mode adaptor type
struct i2c_adapter *adapter
- I2C adapter for the DDC bus
bool *enabled
- current state of the TMDS output buffers
Description
Get the state of the TMDS output buffers in the adaptor. For
type2 adaptors this is queried from the DP_DUAL_MODE_TMDS_OEN
register. As some type 1 adaptors have problems with registers
(see comments in drm_dp_dual_mode_detect()
) we don’t read the
register on those, instead we simply assume that the buffers
are always enabled.
Return
0 on success, negative error code on failure
-
int
drm_dp_dual_mode_set_tmds_output
(enum drm_dp_dual_mode_type type, struct i2c_adapter *adapter, bool enable)¶ Enable/disable TMDS output buffers in the DP dual mode adaptor
Parameters
enum drm_dp_dual_mode_type type
- DP dual mode adaptor type
struct i2c_adapter *adapter
- I2C adapter for the DDC bus
bool enable
- enable (as opposed to disable) the TMDS output buffers
Description
Set the state of the TMDS output buffers in the adaptor. For
type2 this is set via the DP_DUAL_MODE_TMDS_OEN register. As
some type 1 adaptors have problems with registers (see comments
in drm_dp_dual_mode_detect()
) we avoid touching the register,
making this function a no-op on type 1 adaptors.
Return
0 on success, negative error code on failure
-
const char *
drm_dp_get_dual_mode_type_name
(enum drm_dp_dual_mode_type type)¶ Get the name of the DP dual mode adaptor type as a string
Parameters
enum drm_dp_dual_mode_type type
- DP dual mode adaptor type
Return
String representation of the DP dual mode adaptor type
-
int
drm_lspcon_get_mode
(struct i2c_adapter *adapter, enum drm_lspcon_mode *mode)¶
Parameters
struct i2c_adapter *adapter
- I2C-over-aux adapter
enum drm_lspcon_mode *mode
- current lspcon mode of operation output variable
Description
reading offset (0x80, 0x41)
Return
0 on success, sets the current_mode value to appropriate mode -error on failure
-
int
drm_lspcon_set_mode
(struct i2c_adapter *adapter, enum drm_lspcon_mode mode)¶
Parameters
struct i2c_adapter *adapter
- I2C-over-aux adapter
enum drm_lspcon_mode mode
- required mode of operation
Description
writing offset (0x80, 0x40)
Return
0 on success, -error on failure/timeout
Display Port MST Helpers¶
Overview¶
These functions contain parts of the DisplayPort 1.2a MultiStream Transport protocol. The helpers contain a topology manager and bandwidth manager. The helpers encapsulate the sending and received of sideband msgs.
Topology refcount overview¶
The refcounting schemes for struct drm_dp_mst_branch
and struct
drm_dp_mst_port
are somewhat unusual. Both ports and branch devices have
two different kinds of refcounts: topology refcounts, and malloc refcounts.
Topology refcounts are not exposed to drivers, and are handled internally
by the DP MST helpers. The helpers use them in order to prevent the
in-memory topology state from being changed in the middle of critical
operations like changing the internal state of payload allocations. This
means each branch and port will be considered to be connected to the rest
of the topology until its topology refcount reaches zero. Additionally,
for ports this means that their associated struct drm_connector
will stay
registered with userspace until the port’s refcount reaches 0.
Malloc refcount overview¶
Malloc references are used to keep a struct drm_dp_mst_port
or struct
drm_dp_mst_branch
allocated even after all of its topology references have
been dropped, so that the driver or MST helpers can safely access each
branch’s last known state before it was disconnected from the topology.
When the malloc refcount of a port or branch reaches 0, the memory
allocation containing the struct drm_dp_mst_branch
or struct
drm_dp_mst_port
respectively will be freed.
For struct drm_dp_mst_branch
, malloc refcounts are not currently exposed
to drivers. As of writing this documentation, there are no drivers that
have a usecase for accessing struct drm_dp_mst_branch
outside of the MST
helpers. Exposing this API to drivers in a race-free manner would take more
tweaking of the refcounting scheme, however patches are welcome provided
there is a legitimate driver usecase for this.
Refcount relationships in a topology¶
Let’s take a look at why the relationship between topology and malloc refcounts is designed the way it is.
As you can see in the above figure, every branch increments the topology refcount of its children, and increments the malloc refcount of its parent. Additionally, every payload increments the malloc refcount of its assigned port by 1.
So, what would happen if MSTB #3 from the above figure was unplugged from the system, but the driver hadn’t yet removed payload #2 from port #3? The topology would start to look like the figure below.
Whenever a port or branch device’s topology refcount reaches zero, it will
decrement the topology refcounts of all its children, the malloc refcount
of its parent, and finally its own malloc refcount. For MSTB #4 and port
#4, this means they both have been disconnected from the topology and freed
from memory. But, because payload #2 is still holding a reference to port
#3, port #3 is removed from the topology but its struct drm_dp_mst_port
is still accessible from memory. This also means port #3 has not yet
decremented the malloc refcount of MSTB #3, so its struct
drm_dp_mst_branch
will also stay allocated in memory until port #3’s
malloc refcount reaches 0.
This relationship is necessary because in order to release payload #2, we need to be able to figure out the last relative of port #3 that’s still connected to the topology. In this case, we would travel up the topology as shown below.
And finally, remove payload #2 by communicating with port #2 through sideband transactions.
Functions Reference¶
-
struct
drm_dp_vcpi
¶ Virtual Channel Payload Identifier
Definition
struct drm_dp_vcpi {
int vcpi;
int pbn;
int aligned_pbn;
int num_slots;
};
Members
vcpi
- Virtual channel ID.
pbn
- Payload Bandwidth Number for this channel
aligned_pbn
- PBN aligned with slot size
num_slots
- number of slots for this PBN
-
struct
drm_dp_mst_port
¶ MST port
Definition
struct drm_dp_mst_port {
struct kref topology_kref;
struct kref malloc_kref;
#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS);
struct drm_dp_mst_topology_ref_history topology_ref_history;
#endif;
u8 port_num;
bool input;
bool mcs;
bool ddps;
u8 pdt;
bool ldps;
u8 dpcd_rev;
u8 num_sdp_streams;
u8 num_sdp_stream_sinks;
uint16_t full_pbn;
struct list_head next;
struct drm_dp_mst_branch *mstb;
struct drm_dp_aux aux;
struct drm_dp_mst_branch *parent;
struct drm_dp_vcpi vcpi;
struct drm_connector *connector;
struct drm_dp_mst_topology_mgr *mgr;
struct edid *cached_edid;
bool has_audio;
bool fec_capable;
};
Members
topology_kref
- refcount for this port’s lifetime in the topology, only the DP MST helpers should need to touch this
malloc_kref
- refcount for the memory allocation containing this
structure. See
drm_dp_mst_get_port_malloc()
anddrm_dp_mst_put_port_malloc()
. topology_ref_history
- A history of each topology reference/dereference. See CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS.
port_num
- port number
input
- if this port is an input port. Protected by
drm_dp_mst_topology_mgr.base
.lock. mcs
- message capability status - DP 1.2 spec. Protected by
drm_dp_mst_topology_mgr.base
.lock. ddps
- DisplayPort Device Plug Status - DP 1.2. Protected by
drm_dp_mst_topology_mgr.base
.lock. pdt
- Peer Device Type. Protected by
drm_dp_mst_topology_mgr.base
.lock. ldps
- Legacy Device Plug Status. Protected by
drm_dp_mst_topology_mgr.base
.lock. dpcd_rev
- DPCD revision of device on this port. Protected by
drm_dp_mst_topology_mgr.base
.lock. num_sdp_streams
- Number of simultaneous streams. Protected by
drm_dp_mst_topology_mgr.base
.lock. num_sdp_stream_sinks
- Number of stream sinks. Protected by
drm_dp_mst_topology_mgr.base
.lock. full_pbn
- Max possible bandwidth for this port. Protected by
drm_dp_mst_topology_mgr.base
.lock. next
- link to next port on this branch device
mstb
- the branch device connected to this port, if there is one.
This should be considered protected for reading by
drm_dp_mst_topology_mgr.lock
. There are two exceptions to this:drm_dp_mst_topology_mgr.up_req_work
anddrm_dp_mst_topology_mgr.work
, which do not grabdrm_dp_mst_topology_mgr.lock
during reads but are the only updaters of this list and are protected from writing concurrently bydrm_dp_mst_topology_mgr.probe_lock
. aux
- i2c aux transport to talk to device connected to this port, protected
by
drm_dp_mst_topology_mgr.base
.lock. parent
- branch device parent of this port
vcpi
- Virtual Channel Payload info for this port.
connector
- DRM connector this port is connected to. Protected by
drm_dp_mst_topology_mgr.base
.lock. mgr
- topology manager this port lives under.
cached_edid
- for DP logical ports - make tiling work by ensuring that the EDID for all connectors is read immediately.
has_audio
- Tracks whether the sink connector to this port is audio-capable.
fec_capable
- bool indicating if FEC can be supported up to that point in the MST topology.
Description
This structure represents an MST port endpoint on a device somewhere in the MST topology.
-
struct
drm_dp_mst_branch
¶ MST branch device.
Definition
struct drm_dp_mst_branch {
struct kref topology_kref;
struct kref malloc_kref;
#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS);
struct drm_dp_mst_topology_ref_history topology_ref_history;
#endif;
struct list_head destroy_next;
u8 rad[8];
u8 lct;
int num_ports;
struct list_head ports;
struct drm_dp_mst_port *port_parent;
struct drm_dp_mst_topology_mgr *mgr;
bool link_address_sent;
u8 guid[16];
};
Members
topology_kref
- refcount for this branch device’s lifetime in the topology, only the DP MST helpers should need to touch this
malloc_kref
- refcount for the memory allocation containing this
structure. See
drm_dp_mst_get_mstb_malloc()
anddrm_dp_mst_put_mstb_malloc()
. topology_ref_history
- A history of each topology reference/dereference. See CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS.
destroy_next
- linked-list entry used by drm_dp_delayed_destroy_work()
rad
- Relative Address to talk to this branch device.
lct
- Link count total to talk to this branch device.
num_ports
- number of ports on the branch.
ports
- the list of ports on this branch device. This should be
considered protected for reading by
drm_dp_mst_topology_mgr.lock
. There are two exceptions to this:drm_dp_mst_topology_mgr.up_req_work
anddrm_dp_mst_topology_mgr.work
, which do not grabdrm_dp_mst_topology_mgr.lock
during reads but are the only updaters of this list and are protected from updating the list concurrently by drm_dp_mst_topology_mgr.probe_lock port_parent
- pointer to the port parent, NULL if toplevel.
mgr
- topology manager for this branch device.
link_address_sent
- if a link address message has been sent to this device yet.
guid
- guid for DP 1.2 branch device. port under this branch can be identified by port #.
Description
This structure represents an MST branch device, there is one primary branch device at the root, along with any other branches connected to downstream port of parent branches.
-
struct
drm_dp_mst_topology_mgr
¶ DisplayPort MST manager
Definition
struct drm_dp_mst_topology_mgr {
struct drm_private_obj base;
struct drm_device *dev;
const struct drm_dp_mst_topology_cbs *cbs;
int max_dpcd_transaction_bytes;
struct drm_dp_aux *aux;
int max_payloads;
int conn_base_id;
struct drm_dp_sideband_msg_rx up_req_recv;
struct drm_dp_sideband_msg_rx down_rep_recv;
struct mutex lock;
struct mutex probe_lock;
bool mst_state : 1;
bool payload_id_table_cleared : 1;
struct drm_dp_mst_branch *mst_primary;
u8 dpcd[DP_RECEIVER_CAP_SIZE];
u8 sink_count;
int pbn_div;
const struct drm_private_state_funcs *funcs;
struct mutex qlock;
struct list_head tx_msg_downq;
struct mutex payload_lock;
struct drm_dp_vcpi **proposed_vcpis;
struct drm_dp_payload *payloads;
unsigned long payload_mask;
unsigned long vcpi_mask;
wait_queue_head_t tx_waitq;
struct work_struct work;
struct work_struct tx_work;
struct list_head destroy_port_list;
struct list_head destroy_branch_device_list;
struct mutex delayed_destroy_lock;
struct workqueue_struct *delayed_destroy_wq;
struct work_struct delayed_destroy_work;
struct list_head up_req_list;
struct mutex up_req_lock;
struct work_struct up_req_work;
#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS);
struct mutex topology_ref_history_lock;
#endif;
};
Members
base
- Base private object for atomic
dev
- device pointer for adding i2c devices etc.
cbs
- callbacks for connector addition and destruction.
max_dpcd_transaction_bytes
- maximum number of bytes to read/write in one go.
aux
- AUX channel for the DP MST connector this topolgy mgr is controlling.
max_payloads
- maximum number of payloads the GPU can generate.
conn_base_id
- DRM connector ID this mgr is connected to. Only used to build the MST connector path value.
up_req_recv
- Message receiver state for up requests.
down_rep_recv
- Message receiver state for replies to down requests.
lock
- protects mst_state, mst_primary, dpcd, and payload_id_table_cleared.
probe_lock
- Prevents work and up_req_work, the only writers of
drm_dp_mst_port.mstb
anddrm_dp_mst_branch.ports
, from racing while they update the topology. mst_state
- If this manager is enabled for an MST capable port. False if no MST sink/branch devices is connected.
payload_id_table_cleared
- Whether or not we’ve cleared the payload ID table for mst_primary. Protected by lock.
mst_primary
- Pointer to the primary/first branch device.
dpcd
- Cache of DPCD for primary port.
sink_count
- Sink count from DEVICE_SERVICE_IRQ_VECTOR_ESI0.
pbn_div
- PBN to slots divisor.
funcs
- Atomic helper callbacks
qlock
- protects tx_msg_downq and
drm_dp_sideband_msg_tx.state
tx_msg_downq
- List of pending down requests
payload_lock
- Protect payload information.
proposed_vcpis
- Array of pointers for the new VCPI allocation. The
VCPI structure itself is
drm_dp_mst_port.vcpi
, and the size of this array is determined by max_payloads. payloads
- Array of payloads. The size of this array is determined by max_payloads.
payload_mask
- Elements of payloads actually in use. Since reallocation of active outputs isn’t possible gaps can be created by disabling outputs out of order compared to how they’ve been enabled.
vcpi_mask
- Similar to payload_mask, but for proposed_vcpis.
tx_waitq
- Wait to queue stall for the tx worker.
work
- Probe work.
tx_work
- Sideband transmit worker. This can nest within the main work worker for each transaction work launches.
destroy_port_list
- List of to be destroyed connectors.
destroy_branch_device_list
- List of to be destroyed branch devices.
delayed_destroy_lock
- Protects destroy_port_list and destroy_branch_device_list.
delayed_destroy_wq
- Workqueue used for delayed_destroy_work items. A dedicated WQ makes it possible to drain any requeued work items on it.
delayed_destroy_work
- Work item to destroy MST port and branch devices, needed to avoid locking inversion.
up_req_list
- List of pending up requests from the topology that need to be processed, in chronological order.
up_req_lock
- Protects up_req_list
up_req_work
- Work item to process up requests received from the topology. Needed to avoid blocking hotplug handling and sideband transmissions.
topology_ref_history_lock
- protects
drm_dp_mst_port.topology_ref_history
anddrm_dp_mst_branch.topology_ref_history
.
Description
This struct represents the toplevel displayport MST topology manager. There should be one instance of this for every MST capable DP connector on the GPU.
-
bool
__drm_dp_mst_state_iter_get
(struct drm_atomic_state *state, struct drm_dp_mst_topology_mgr **mgr, struct drm_dp_mst_topology_state **old_state, struct drm_dp_mst_topology_state **new_state, int i)¶ private atomic state iterator function for macro-internal use
Parameters
struct drm_atomic_state *state
struct drm_atomic_state
pointerstruct drm_dp_mst_topology_mgr **mgr
- pointer to the
struct drm_dp_mst_topology_mgr
iteration cursor struct drm_dp_mst_topology_state **old_state
- optional pointer to the old
struct drm_dp_mst_topology_state
iteration cursor struct drm_dp_mst_topology_state **new_state
- optional pointer to the new
struct drm_dp_mst_topology_state
iteration cursor int i
- int iteration cursor, for macro-internal use
Description
Used by for_each_oldnew_mst_mgr_in_state()
,
for_each_old_mst_mgr_in_state()
, and for_each_new_mst_mgr_in_state()
. Don’t
call this directly.
Return
True if the current struct drm_private_obj
is a struct
drm_dp_mst_topology_mgr
, false otherwise.
-
for_each_oldnew_mst_mgr_in_state
(__state, mgr, old_state, new_state, __i)¶ iterate over all DP MST topology managers in an atomic update
Parameters
__state
struct drm_atomic_state
pointermgr
struct drm_dp_mst_topology_mgr
iteration cursorold_state
struct drm_dp_mst_topology_state
iteration cursor for the old statenew_state
struct drm_dp_mst_topology_state
iteration cursor for the new state__i
- int iteration cursor, for macro-internal use
Description
This iterates over all DRM DP MST topology managers in an atomic update, tracking both old and new state. This is useful in places where the state delta needs to be considered, for example in atomic check functions.
-
for_each_old_mst_mgr_in_state
(__state, mgr, old_state, __i)¶ iterate over all DP MST topology managers in an atomic update
Parameters
__state
struct drm_atomic_state
pointermgr
struct drm_dp_mst_topology_mgr
iteration cursorold_state
struct drm_dp_mst_topology_state
iteration cursor for the old state__i
- int iteration cursor, for macro-internal use
Description
This iterates over all DRM DP MST topology managers in an atomic update, tracking only the old state. This is useful in disable functions, where we need the old state the hardware is still in.
-
for_each_new_mst_mgr_in_state
(__state, mgr, new_state, __i)¶ iterate over all DP MST topology managers in an atomic update
Parameters
__state
struct drm_atomic_state
pointermgr
struct drm_dp_mst_topology_mgr
iteration cursornew_state
struct drm_dp_mst_topology_state
iteration cursor for the new state__i
- int iteration cursor, for macro-internal use
Description
This iterates over all DRM DP MST topology managers in an atomic update, tracking only the new state. This is useful in enable functions, where we need the new state the hardware should be in when the atomic commit operation has completed.
-
void
drm_dp_mst_get_port_malloc
(struct drm_dp_mst_port *port)¶ Increment the malloc refcount of an MST port
Parameters
struct drm_dp_mst_port *port
- The
struct drm_dp_mst_port
to increment the malloc refcount of
Description
Increments drm_dp_mst_port.malloc_kref
. When drm_dp_mst_port.malloc_kref
reaches 0, the memory allocation for port will be released and port may
no longer be used.
Because port could potentially be freed at any time by the DP MST helpers
if drm_dp_mst_port.malloc_kref
reaches 0, including during a call to this
function, drivers that which to make use of struct drm_dp_mst_port
should
ensure that they grab at least one main malloc reference to their MST ports
in drm_dp_mst_topology_cbs.add_connector
. This callback is called before
there is any chance for drm_dp_mst_port.malloc_kref
to reach 0.
See also: drm_dp_mst_put_port_malloc()
-
void
drm_dp_mst_put_port_malloc
(struct drm_dp_mst_port *port)¶ Decrement the malloc refcount of an MST port
Parameters
struct drm_dp_mst_port *port
- The
struct drm_dp_mst_port
to decrement the malloc refcount of
Description
Decrements drm_dp_mst_port.malloc_kref
. When drm_dp_mst_port.malloc_kref
reaches 0, the memory allocation for port will be released and port may
no longer be used.
See also: drm_dp_mst_get_port_malloc()
-
int
drm_dp_mst_connector_late_register
(struct drm_connector *connector, struct drm_dp_mst_port *port)¶ Late MST connector registration
Parameters
struct drm_connector *connector
- The MST connector
struct drm_dp_mst_port *port
- The MST port for this connector
Description
Helper to register the remote aux device for this MST port. Drivers should call this from their mst connector’s late_register hook to enable MST aux devices.
Return
0 on success, negative error code on failure.
-
void
drm_dp_mst_connector_early_unregister
(struct drm_connector *connector, struct drm_dp_mst_port *port)¶ Early MST connector unregistration
Parameters
struct drm_connector *connector
- The MST connector
struct drm_dp_mst_port *port
- The MST port for this connector
Description
Helper to unregister the remote aux device for this MST port, registered by
drm_dp_mst_connector_late_register()
. Drivers should call this from their mst
connector’s early_unregister hook.
-
int
drm_dp_update_payload_part1
(struct drm_dp_mst_topology_mgr *mgr)¶ Execute payload update part 1
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager to use.
Description
This iterates over all proposed virtual channels, and tries to allocate space in the link for them. For 0->slots transitions, this step just writes the VCPI to the MST device. For slots->0 transitions, this writes the updated VCPIs and removes the remote VC payloads.
after calling this the driver should generate ACT and payload packets.
-
int
drm_dp_update_payload_part2
(struct drm_dp_mst_topology_mgr *mgr)¶ Execute payload update part 2
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager to use.
Description
This iterates over all proposed virtual channels, and tries to allocate space in the link for them. For 0->slots transitions, this step writes the remote VC payload commands. For slots->0 this just resets some internal state.
-
int
drm_dp_get_vc_payload_bw
(int link_rate, int link_lane_count)¶ get the VC payload BW for an MST link
Parameters
int link_rate
- link rate in 10kbits/s units
int link_lane_count
- lane count
Description
Calculate the total bandwidth of a MultiStream Transport link. The returned value is in units of PBNs/(timeslots/1 MTP). This value can be used to convert the number of PBNs required for a given stream to the number of timeslots this stream requires in each MTP.
-
bool
drm_dp_read_mst_cap
(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIVER_CAP_SIZE])¶ check whether or not a sink supports MST
Parameters
struct drm_dp_aux *aux
- The DP AUX channel to use
const u8 dpcd[DP_RECEIVER_CAP_SIZE]
- A cached copy of the DPCD capabilities for this sink
Return
True
if the sink supports MST, false
otherwise
-
int
drm_dp_mst_topology_mgr_set_mst
(struct drm_dp_mst_topology_mgr *mgr, bool mst_state)¶ Set the MST state for a topology manager
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager to set state for
bool mst_state
- true to enable MST on this connector - false to disable.
Description
This is called by the driver when it detects an MST capable device plugged into a DP MST capable port, or when a DP MST capable device is unplugged.
-
void
drm_dp_mst_topology_mgr_suspend
(struct drm_dp_mst_topology_mgr *mgr)¶ suspend the MST manager
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager to suspend
Description
This function tells the MST device that we can’t handle UP messages anymore. This should stop it from sending any since we are suspended.
-
int
drm_dp_mst_topology_mgr_resume
(struct drm_dp_mst_topology_mgr *mgr, bool sync)¶ resume the MST manager
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager to resume
bool sync
- whether or not to perform topology reprobing synchronously
Description
This will fetch DPCD and see if the device is still there, if it is, it will rewrite the MSTM control bits, and return.
If the device fails this returns -1, and the driver should do a full MST reprobe, in case we were undocked.
During system resume (where it is assumed that the driver will be calling
drm_atomic_helper_resume()
) this function should be called beforehand with
sync set to true. In contexts like runtime resume where the driver is not
expected to be calling drm_atomic_helper_resume()
, this function should be
called with sync set to false in order to avoid deadlocking.
Return
-1 if the MST topology was removed while we were suspended, 0 otherwise.
-
int
drm_dp_mst_hpd_irq
(struct drm_dp_mst_topology_mgr *mgr, u8 *esi, bool *handled)¶ MST hotplug IRQ notify
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager to notify irq for.
u8 *esi
- 4 bytes from SINK_COUNT_ESI
bool *handled
- whether the hpd interrupt was consumed or not
Description
This should be called from the driver when it detects a short IRQ, along with the value of the DEVICE_SERVICE_IRQ_VECTOR_ESI0. The topology manager will process the sideband messages received as a result of this.
-
int
drm_dp_mst_detect_port
(struct drm_connector *connector, struct drm_modeset_acquire_ctx *ctx, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)¶ get connection status for an MST port
Parameters
struct drm_connector *connector
- DRM connector for this port
struct drm_modeset_acquire_ctx *ctx
- The acquisition context to use for grabbing locks
struct drm_dp_mst_topology_mgr *mgr
- manager for this port
struct drm_dp_mst_port *port
- pointer to a port
Description
This returns the current connection state for a port.
-
struct edid *
drm_dp_mst_get_edid
(struct drm_connector *connector, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)¶ get EDID for an MST port
Parameters
struct drm_connector *connector
- toplevel connector to get EDID for
struct drm_dp_mst_topology_mgr *mgr
- manager for this port
struct drm_dp_mst_port *port
- unverified pointer to a port.
Description
This returns an EDID for the port connected to a connector, It validates the pointer still exists so the caller doesn’t require a reference.
-
int
drm_dp_find_vcpi_slots
(struct drm_dp_mst_topology_mgr *mgr, int pbn)¶ Find VCPI slots for this PBN value
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager to use
int pbn
- payload bandwidth to convert into slots.
Description
Calculate the number of VCPI slots that will be required for the given PBN value. This function is deprecated, and should not be used in atomic drivers.
Return
The total slots required for this port, or error.
-
int
drm_dp_atomic_find_vcpi_slots
(struct drm_atomic_state *state, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port, int pbn, int pbn_div)¶ Find and add VCPI slots to the state
Parameters
struct drm_atomic_state *state
- global atomic state
struct drm_dp_mst_topology_mgr *mgr
- MST topology manager for the port
struct drm_dp_mst_port *port
- port to find vcpi slots for
int pbn
- bandwidth required for the mode in PBN
int pbn_div
- divider for DSC mode that takes FEC into account
Description
Allocates VCPI slots to port, replacing any previous VCPI allocations it
may have had. Any atomic drivers which support MST must call this function
in their drm_encoder_helper_funcs.atomic_check()
callback to change the
current VCPI allocation for the new state, but only when
drm_crtc_state.mode_changed
or drm_crtc_state.connectors_changed
is set
to ensure compatibility with userspace applications that still use the
legacy modesetting UAPI.
Allocations set by this function are not checked against the bandwidth
restraints of mgr until the driver calls drm_dp_mst_atomic_check()
.
Additionally, it is OK to call this function multiple times on the same
port as needed. It is not OK however, to call this function and
drm_dp_atomic_release_vcpi_slots()
in the same atomic check phase.
See also:
drm_dp_atomic_release_vcpi_slots()
drm_dp_mst_atomic_check()
Return
Total slots in the atomic state assigned for this port, or a negative error code if the port no longer exists
-
int
drm_dp_atomic_release_vcpi_slots
(struct drm_atomic_state *state, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)¶ Release allocated vcpi slots
Parameters
struct drm_atomic_state *state
- global atomic state
struct drm_dp_mst_topology_mgr *mgr
- MST topology manager for the port
struct drm_dp_mst_port *port
- The port to release the VCPI slots from
Description
Releases any VCPI slots that have been allocated to a port in the atomic
state. Any atomic drivers which support MST must call this function in
their drm_connector_helper_funcs.atomic_check()
callback when the
connector will no longer have VCPI allocated (e.g. because its CRTC was
removed) when it had VCPI allocated in the previous atomic state.
It is OK to call this even if port has been removed from the system.
Additionally, it is OK to call this function multiple times on the same
port as needed. It is not OK however, to call this function and
drm_dp_atomic_find_vcpi_slots()
on the same port in a single atomic check
phase.
See also:
drm_dp_atomic_find_vcpi_slots()
drm_dp_mst_atomic_check()
Return
0 if all slots for this port were added back to
drm_dp_mst_topology_state.avail_slots
or negative error code
-
bool
drm_dp_mst_allocate_vcpi
(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port, int pbn, int slots)¶ Allocate a virtual channel
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager for this port
struct drm_dp_mst_port *port
- port to allocate a virtual channel for.
int pbn
- payload bandwidth number to request
int slots
- returned number of slots for this PBN.
-
void
drm_dp_mst_reset_vcpi_slots
(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)¶ Reset number of slots to 0 for VCPI
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager for this port
struct drm_dp_mst_port *port
- unverified pointer to a port.
Description
This just resets the number of slots for the ports VCPI for later programming.
-
void
drm_dp_mst_deallocate_vcpi
(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)¶ deallocate a VCPI
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager for this port
struct drm_dp_mst_port *port
- port to deallocate vcpi for
Description
This can be called unconditionally, regardless of whether
drm_dp_mst_allocate_vcpi()
succeeded or not.
-
int
drm_dp_check_act_status
(struct drm_dp_mst_topology_mgr *mgr)¶ Polls for ACT handled status.
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager to use
Description
Tries waiting for the MST hub to finish updating it’s payload table by polling for the ACT handled bit for up to 3 seconds (yes-some hubs really take that long).
Return
0 if the ACT was handled in time, negative error code on failure.
-
int
drm_dp_calc_pbn_mode
(int clock, int bpp, bool dsc)¶ Calculate the PBN for a mode.
Parameters
int clock
- dot clock for the mode
int bpp
- bpp for the mode.
bool dsc
- DSC mode. If true, bpp has units of 1/16 of a bit per pixel
Description
This uses the formula in the spec to calculate the PBN value for a mode.
-
void
drm_dp_mst_dump_topology
(struct seq_file *m, struct drm_dp_mst_topology_mgr *mgr)¶
Parameters
struct seq_file *m
- seq_file to dump output to
struct drm_dp_mst_topology_mgr *mgr
- manager to dump current topology for.
Description
helper to dump MST topology to a seq file for debugfs.
-
int
drm_dp_mst_add_affected_dsc_crtcs
(struct drm_atomic_state *state, struct drm_dp_mst_topology_mgr *mgr)¶
Parameters
struct drm_atomic_state *state
- Pointer to the new struct drm_dp_mst_topology_state
struct drm_dp_mst_topology_mgr *mgr
- MST topology manager
Description
Whenever there is a change in mst topology DSC configuration would have to be recalculated therefore we need to trigger modeset on all affected CRTCs in that topology
See also:
drm_dp_mst_atomic_enable_dsc()
-
int
drm_dp_mst_atomic_enable_dsc
(struct drm_atomic_state *state, struct drm_dp_mst_port *port, int pbn, int pbn_div, bool enable)¶ Set DSC Enable Flag to On/Off
Parameters
struct drm_atomic_state *state
- Pointer to the new drm_atomic_state
struct drm_dp_mst_port *port
- Pointer to the affected MST Port
int pbn
- Newly recalculated bw required for link with DSC enabled
int pbn_div
- Divider to calculate correct number of pbn per slot
bool enable
- Boolean flag to enable or disable DSC on the port
Description
This function enables DSC on the given Port by recalculating its vcpi from pbn provided and sets dsc_enable flag to keep track of which ports have DSC enabled
-
int
drm_dp_mst_atomic_check
(struct drm_atomic_state *state)¶ Check that the new state of an MST topology in an atomic update is valid
Parameters
struct drm_atomic_state *state
- Pointer to the new
struct drm_dp_mst_topology_state
Description
Checks the given topology state for an atomic update to ensure that it’s valid. This includes checking whether there’s enough bandwidth to support the new VCPI allocations in the atomic update.
Any atomic drivers supporting DP MST must make sure to call this after
checking the rest of their state in their
drm_mode_config_funcs.atomic_check()
callback.
See also:
drm_dp_atomic_find_vcpi_slots()
drm_dp_atomic_release_vcpi_slots()
0 if the new state is valid, negative error code otherwise.
Return
-
struct drm_dp_mst_topology_state *
drm_atomic_get_mst_topology_state
(struct drm_atomic_state *state, struct drm_dp_mst_topology_mgr *mgr)¶
Parameters
struct drm_atomic_state *state
- global atomic state
struct drm_dp_mst_topology_mgr *mgr
- MST topology manager, also the private object in this case
Description
This function wraps drm_atomic_get_priv_obj_state() passing in the MST atomic
state vtable so that the private object state returned is that of a MST
topology object. Also, drm_atomic_get_private_obj_state()
expects the caller
to care of the locking, so warn if don’t hold the connection_mutex.
The MST topology state or error pointer.
Return
-
int
drm_dp_mst_topology_mgr_init
(struct drm_dp_mst_topology_mgr *mgr, struct drm_device *dev, struct drm_dp_aux *aux, int max_dpcd_transaction_bytes, int max_payloads, int conn_base_id)¶ initialise a topology manager
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager struct to initialise
struct drm_device *dev
- device providing this structure - for i2c addition.
struct drm_dp_aux *aux
- DP helper aux channel to talk to this device
int max_dpcd_transaction_bytes
- hw specific DPCD transaction limit
int max_payloads
- maximum number of payloads this GPU can source
int conn_base_id
- the connector object ID the MST device is connected to.
Description
Return 0 for success, or negative error code on failure
-
void
drm_dp_mst_topology_mgr_destroy
(struct drm_dp_mst_topology_mgr *mgr)¶ destroy topology manager.
Parameters
struct drm_dp_mst_topology_mgr *mgr
- manager to destroy
-
struct drm_dp_aux *
drm_dp_mst_dsc_aux_for_port
(struct drm_dp_mst_port *port)¶ Find the correct aux for DSC
Parameters
struct drm_dp_mst_port *port
- The port to check. A leaf of the MST tree with an attached display.
Description
Depending on the situation, DSC may be enabled via the endpoint aux, the immediately upstream aux, or the connector’s physical aux.
This is both the correct aux to read DSC_CAPABILITY and the correct aux to write DSC_ENABLED.
This operation can be expensive (up to four aux reads), so the caller should cache the return.
Return
NULL if DSC cannot be enabled on this port, otherwise the aux device
Topology Lifetime Internals¶
These functions aren’t exported to drivers, but are documented here to help make the MST topology helpers easier to understand
-
void
drm_dp_mst_get_mstb_malloc
(struct drm_dp_mst_branch *mstb)¶ Increment the malloc refcount of a branch device
Parameters
struct drm_dp_mst_branch *mstb
- The
struct drm_dp_mst_branch
to increment the malloc refcount of
Description
Increments drm_dp_mst_branch.malloc_kref
. When
drm_dp_mst_branch.malloc_kref
reaches 0, the memory allocation for mstb
will be released and mstb may no longer be used.
See also: drm_dp_mst_put_mstb_malloc()
-
void
drm_dp_mst_put_mstb_malloc
(struct drm_dp_mst_branch *mstb)¶ Decrement the malloc refcount of a branch device
Parameters
struct drm_dp_mst_branch *mstb
- The
struct drm_dp_mst_branch
to decrement the malloc refcount of
Description
Decrements drm_dp_mst_branch.malloc_kref
. When
drm_dp_mst_branch.malloc_kref
reaches 0, the memory allocation for mstb
will be released and mstb may no longer be used.
See also: drm_dp_mst_get_mstb_malloc()
-
int
drm_dp_mst_topology_try_get_mstb
(struct drm_dp_mst_branch *mstb)¶ Increment the topology refcount of a branch device unless it’s zero
Parameters
struct drm_dp_mst_branch *mstb
struct drm_dp_mst_branch
to increment the topology refcount of
Description
Attempts to grab a topology reference to mstb, if it hasn’t yet been
removed from the topology (e.g. drm_dp_mst_branch.topology_kref
has
reached 0). Holding a topology reference implies that a malloc reference
will be held to mstb as long as the user holds the topology reference.
Care should be taken to ensure that the user has at least one malloc
reference to mstb. If you already have a topology reference to mstb, you
should use drm_dp_mst_topology_get_mstb()
instead.
See also:
drm_dp_mst_topology_get_mstb()
drm_dp_mst_topology_put_mstb()
Return
- 1: A topology reference was grabbed successfully
- 0: port is no longer in the topology, no reference was grabbed
-
void
drm_dp_mst_topology_get_mstb
(struct drm_dp_mst_branch *mstb)¶ Increment the topology refcount of a branch device
Parameters
struct drm_dp_mst_branch *mstb
- The
struct drm_dp_mst_branch
to increment the topology refcount of
Description
Increments drm_dp_mst_branch.topology_refcount
without checking whether or
not it’s already reached 0. This is only valid to use in scenarios where
you are already guaranteed to have at least one active topology reference
to mstb. Otherwise, drm_dp_mst_topology_try_get_mstb()
must be used.
See also:
drm_dp_mst_topology_try_get_mstb()
drm_dp_mst_topology_put_mstb()
-
void
drm_dp_mst_topology_put_mstb
(struct drm_dp_mst_branch *mstb)¶ release a topology reference to a branch device
Parameters
struct drm_dp_mst_branch *mstb
- The
struct drm_dp_mst_branch
to release the topology reference from
Description
Releases a topology reference from mstb by decrementing
drm_dp_mst_branch.topology_kref
.
See also:
drm_dp_mst_topology_try_get_mstb()
drm_dp_mst_topology_get_mstb()
-
int
drm_dp_mst_topology_try_get_port
(struct drm_dp_mst_port *port)¶ Increment the topology refcount of a port unless it’s zero
Parameters
struct drm_dp_mst_port *port
struct drm_dp_mst_port
to increment the topology refcount of
Description
Attempts to grab a topology reference to port, if it hasn’t yet been
removed from the topology (e.g. drm_dp_mst_port.topology_kref
has reached
0). Holding a topology reference implies that a malloc reference will be
held to port as long as the user holds the topology reference.
Care should be taken to ensure that the user has at least one malloc
reference to port. If you already have a topology reference to port, you
should use drm_dp_mst_topology_get_port()
instead.
See also:
drm_dp_mst_topology_get_port()
drm_dp_mst_topology_put_port()
Return
- 1: A topology reference was grabbed successfully
- 0: port is no longer in the topology, no reference was grabbed
-
void
drm_dp_mst_topology_get_port
(struct drm_dp_mst_port *port)¶ Increment the topology refcount of a port
Parameters
struct drm_dp_mst_port *port
- The
struct drm_dp_mst_port
to increment the topology refcount of
Description
Increments drm_dp_mst_port.topology_refcount
without checking whether or
not it’s already reached 0. This is only valid to use in scenarios where
you are already guaranteed to have at least one active topology reference
to port. Otherwise, drm_dp_mst_topology_try_get_port()
must be used.
See also:
drm_dp_mst_topology_try_get_port()
drm_dp_mst_topology_put_port()
-
void
drm_dp_mst_topology_put_port
(struct drm_dp_mst_port *port)¶ release a topology reference to a port
Parameters
struct drm_dp_mst_port *port
- The
struct drm_dp_mst_port
to release the topology reference from
Description
Releases a topology reference from port by decrementing
drm_dp_mst_port.topology_kref
.
See also:
drm_dp_mst_topology_try_get_port()
drm_dp_mst_topology_get_port()
MIPI DBI Helper Functions Reference¶
This library provides helpers for MIPI Display Bus Interface (DBI) compatible display controllers.
Many controllers for tiny lcd displays are MIPI compliant and can use this library. If a controller uses registers 0x2A and 0x2B to set the area to update and uses register 0x2C to write to frame memory, it is most likely MIPI compliant.
Only MIPI Type 1 displays are supported since a full frame memory is needed.
There are 3 MIPI DBI implementation types:
- Motorola 6800 type parallel bus
- Intel 8080 type parallel bus
- SPI type with 3 options:
- 9-bit with the Data/Command signal as the ninth bit
- Same as above except it’s sent as 16 bits
- 8-bit with the Data/Command signal as a separate D/CX pin
Currently mipi_dbi only supports Type C options 1 and 3 with
mipi_dbi_spi_init()
.
-
struct
mipi_dbi
¶ MIPI DBI interface
Definition
struct mipi_dbi {
struct mutex cmdlock;
int (*command)(struct mipi_dbi *dbi, u8 *cmd, u8 *param, size_t num);
const u8 *read_commands;
bool swap_bytes;
struct gpio_desc *reset;
struct spi_device *spi;
struct gpio_desc *dc;
void *tx_buf9;
size_t tx_buf9_len;
};
Members
cmdlock
- Command lock
command
- Bus specific callback executing commands.
read_commands
- Array of read commands terminated by a zero entry.
- Reading is disabled if this is NULL.
swap_bytes
- Swap bytes in buffer before transfer
reset
- Optional reset gpio
spi
- SPI device
dc
- Optional D/C gpio.
tx_buf9
- Buffer used for Option 1 9-bit conversion
tx_buf9_len
- Size of tx_buf9.
-
struct
mipi_dbi_dev
¶ MIPI DBI device
Definition
struct mipi_dbi_dev {
struct drm_device drm;
struct drm_simple_display_pipe pipe;
struct drm_connector connector;
struct drm_display_mode mode;
u16 *tx_buf;
unsigned int rotation;
unsigned int left_offset;
unsigned int top_offset;
struct backlight_device *backlight;
struct regulator *regulator;
struct mipi_dbi dbi;
};
Members
drm
- DRM device
pipe
- Display pipe structure
connector
- Connector
mode
- Fixed display mode
tx_buf
- Buffer used for transfer (copy clip rect area)
rotation
- initial rotation in degrees Counter Clock Wise
left_offset
- Horizontal offset of the display relative to the
- controller’s driver array
top_offset
- Vertical offset of the display relative to the
- controller’s driver array
backlight
- backlight device (optional)
regulator
- power regulator (optional)
dbi
- MIPI DBI interface
-
mipi_dbi_command
(dbi, cmd, seq…)¶ MIPI DCS command with optional parameter(s)
Parameters
dbi
- MIPI DBI structure
cmd
- Command
seq...
- Optional parameter(s)
Description
Send MIPI DCS command to the controller. Use mipi_dbi_command_read()
for
get/read.
Return
Zero on success, negative error code on failure.
Parameters
struct mipi_dbi *dbi
- MIPI DBI structure
u8 cmd
- Command
u8 *val
- Value read
Description
Send MIPI DCS read command to the controller.
Return
Zero on success, negative error code on failure.
-
int
mipi_dbi_command_buf
(struct mipi_dbi *dbi, u8 cmd, u8 *data, size_t len)¶ MIPI DCS command with parameter(s) in an array
Parameters
struct mipi_dbi *dbi
- MIPI DBI structure
u8 cmd
- Command
u8 *data
- Parameter buffer
size_t len
- Buffer length
Return
Zero on success, negative error code on failure.
-
int
mipi_dbi_buf_copy
(void *dst, struct drm_framebuffer *fb, struct drm_rect *clip, bool swap)¶ Copy a framebuffer, transforming it if necessary
Parameters
void *dst
- The destination buffer
struct drm_framebuffer *fb
- The source framebuffer
struct drm_rect *clip
- Clipping rectangle of the area to be copied
bool swap
- When true, swap MSB/LSB of 16-bit values
Return
Zero on success, negative error code on failure.
-
void
mipi_dbi_pipe_update
(struct drm_simple_display_pipe *pipe, struct drm_plane_state *old_state)¶ Display pipe update helper
Parameters
struct drm_simple_display_pipe *pipe
- Simple display pipe
struct drm_plane_state *old_state
- Old plane state
Description
This function handles framebuffer flushing and vblank events. Drivers can use
this as their drm_simple_display_pipe_funcs->update
callback.
-
void
mipi_dbi_enable_flush
(struct mipi_dbi_dev *dbidev, struct drm_crtc_state *crtc_state, struct drm_plane_state *plane_state)¶ MIPI DBI enable helper
Parameters
struct mipi_dbi_dev *dbidev
- MIPI DBI device structure
struct drm_crtc_state *crtc_state
- CRTC state
struct drm_plane_state *plane_state
- Plane state
Description
Flushes the whole framebuffer and enables the backlight. Drivers can use this
in their drm_simple_display_pipe_funcs->enable
callback.
Note
Drivers which don’t use mipi_dbi_pipe_update()
because they have custom
framebuffer flushing, can’t use this function since they both use the same
flushing code.
-
void
mipi_dbi_pipe_disable
(struct drm_simple_display_pipe *pipe)¶ MIPI DBI pipe disable helper
Parameters
struct drm_simple_display_pipe *pipe
- Display pipe
Description
This function disables backlight if present, if not the display memory is
blanked. The regulator is disabled if in use. Drivers can use this as their
drm_simple_display_pipe_funcs->disable
callback.
-
int
mipi_dbi_dev_init_with_formats
(struct mipi_dbi_dev *dbidev, const struct drm_simple_display_pipe_funcs *funcs, const uint32_t *formats, unsigned int format_count, const struct drm_display_mode *mode, unsigned int rotation, size_t tx_buf_size)¶ MIPI DBI device initialization with custom formats
Parameters
struct mipi_dbi_dev *dbidev
- MIPI DBI device structure to initialize
const struct drm_simple_display_pipe_funcs *funcs
- Display pipe functions
const uint32_t *formats
- Array of supported formats (DRM_FORMAT_*).
unsigned int format_count
- Number of elements in formats
const struct drm_display_mode *mode
- Display mode
unsigned int rotation
- Initial rotation in degrees Counter Clock Wise
size_t tx_buf_size
- Allocate a transmit buffer of this size.
Description
This function sets up a drm_simple_display_pipe
with a drm_connector
that
has one fixed drm_display_mode
which is rotated according to rotation.
This mode is used to set the mode config min/max width/height properties.
Use mipi_dbi_dev_init()
if you don’t need custom formats.
Note
Some of the helper functions expects RGB565 to be the default format and the transmit buffer sized to fit that.
Return
Zero on success, negative error code on failure.
-
int
mipi_dbi_dev_init
(struct mipi_dbi_dev *dbidev, const struct drm_simple_display_pipe_funcs *funcs, const struct drm_display_mode *mode, unsigned int rotation)¶ MIPI DBI device initialization
Parameters
struct mipi_dbi_dev *dbidev
- MIPI DBI device structure to initialize
const struct drm_simple_display_pipe_funcs *funcs
- Display pipe functions
const struct drm_display_mode *mode
- Display mode
unsigned int rotation
- Initial rotation in degrees Counter Clock Wise
Description
This function sets up a drm_simple_display_pipe
with a drm_connector
that
has one fixed drm_display_mode
which is rotated according to rotation.
This mode is used to set the mode config min/max width/height properties.
Additionally mipi_dbi.tx_buf
is allocated.
Supported formats: Native RGB565 and emulated XRGB8888.
Return
Zero on success, negative error code on failure.
Parameters
struct mipi_dbi *dbi
- MIPI DBI structure
Description
Reset controller if the mipi_dbi->reset
gpio is set.
Parameters
struct mipi_dbi *dbi
- MIPI DBI structure
Description
This function checks the Power Mode register (if readable) to see if display output is turned on. This can be used to see if the bootloader has already turned on the display avoiding flicker when the pipeline is enabled.
Return
true if the display can be verified to be on, false otherwise.
-
int
mipi_dbi_poweron_reset
(struct mipi_dbi_dev *dbidev)¶ MIPI DBI poweron and reset
Parameters
struct mipi_dbi_dev *dbidev
- MIPI DBI device structure
Description
This function enables the regulator if used and does a hardware and software reset.
Return
Zero on success, or a negative error code.
-
int
mipi_dbi_poweron_conditional_reset
(struct mipi_dbi_dev *dbidev)¶ MIPI DBI poweron and conditional reset
Parameters
struct mipi_dbi_dev *dbidev
- MIPI DBI device structure
Description
This function enables the regulator if used and if the display is off, it
does a hardware and software reset. If mipi_dbi_display_is_on()
determines
that the display is on, no reset is performed.
Return
Zero if the controller was reset, 1 if the display was already on, or a negative error code.
-
u32
mipi_dbi_spi_cmd_max_speed
(struct spi_device *spi, size_t len)¶ get the maximum SPI bus speed
Parameters
struct spi_device *spi
- SPI device
size_t len
- The transfer buffer length.
Description
Many controllers have a max speed of 10MHz, but can be pushed way beyond that. Increase reliability by running pixel data at max speed and the rest at 10MHz, preventing transfer glitches from messing up the init settings.
-
int
mipi_dbi_spi_init
(struct spi_device *spi, struct mipi_dbi *dbi, struct gpio_desc *dc)¶ Initialize MIPI DBI SPI interface
Parameters
struct spi_device *spi
- SPI device
struct mipi_dbi *dbi
- MIPI DBI structure to initialize
struct gpio_desc *dc
- D/C gpio (optional)
Description
This function sets mipi_dbi->command
, enables mipi_dbi->read_commands
for the
usual read commands. It should be followed by a call to mipi_dbi_dev_init()
or
a driver-specific init.
If dc is set, a Type C Option 3 interface is assumed, if not Type C Option 1.
If the SPI master driver doesn’t support the necessary bits per word, the following transformation is used:
- 9-bit: reorder buffer as 9x 8-bit words, padded with no-op command.
- 16-bit: if big endian send as 8-bit, if little endian swap bytes
Return
Zero on success, negative error code on failure.
-
int
mipi_dbi_spi_transfer
(struct spi_device *spi, u32 speed_hz, u8 bpw, const void *buf, size_t len)¶ SPI transfer helper
Parameters
struct spi_device *spi
- SPI device
u32 speed_hz
- Override speed (optional)
u8 bpw
- Bits per word
const void *buf
- Buffer to transfer
size_t len
- Buffer length
Description
This SPI transfer helper breaks up the transfer of buf into chunks which the SPI controller driver can handle.
Return
Zero on success, negative error code on failure.
Parameters
struct drm_minor *minor
- DRM minor
Description
This function creates a ‘command’ debugfs file for sending commands to the
controller or getting the read command values.
Drivers can use this as their drm_driver->debugfs_init
callback.
MIPI DSI Helper Functions Reference¶
These functions contain some common logic and helpers to deal with MIPI DSI peripherals.
Helpers are provided for a number of standard MIPI DSI command as well as a subset of the MIPI DCS command set.
-
struct
mipi_dsi_msg
¶ read/write DSI buffer
Definition
struct mipi_dsi_msg {
u8 channel;
u8 type;
u16 flags;
size_t tx_len;
const void *tx_buf;
size_t rx_len;
void *rx_buf;
};
Members
channel
- virtual channel id
type
- payload data type
flags
- flags controlling this message transmission
tx_len
- length of tx_buf
tx_buf
- data to be written
rx_len
- length of rx_buf
rx_buf
- data to be read, or NULL
-
struct
mipi_dsi_packet
¶ represents a MIPI DSI packet in protocol format
Definition
struct mipi_dsi_packet {
size_t size;
u8 header[4];
size_t payload_length;
const u8 *payload;
};
Members
size
- size (in bytes) of the packet
header
- the four bytes that make up the header (Data ID, Word Count or Packet Data, and ECC)
payload_length
- number of bytes in the payload
payload
- a pointer to a buffer containing the payload, if any
-
struct
mipi_dsi_host_ops
¶ DSI bus operations
Definition
struct mipi_dsi_host_ops {
int (*attach)(struct mipi_dsi_host *host, struct mipi_dsi_device *dsi);
int (*detach)(struct mipi_dsi_host *host, struct mipi_dsi_device *dsi);
ssize_t (*transfer)(struct mipi_dsi_host *host, const struct mipi_dsi_msg *msg);
};
Members
attach
- attach DSI device to DSI host
detach
- detach DSI device from DSI host
transfer
- transmit a DSI packet
Description
DSI packets transmitted by .transfer() are passed in as mipi_dsi_msg structures. This structure contains information about the type of packet being transmitted as well as the transmit and receive buffers. When an error is encountered during transmission, this function will return a negative error code. On success it shall return the number of bytes transmitted for write packets or the number of bytes received for read packets.
Note that typically DSI packet transmission is atomic, so the .transfer() function will seldomly return anything other than the number of bytes contained in the transmit buffer on success.
-
struct
mipi_dsi_host
¶ DSI host device
Definition
struct mipi_dsi_host {
struct device *dev;
const struct mipi_dsi_host_ops *ops;
struct list_head list;
};
Members
dev
- driver model device node for this DSI host
ops
- DSI host operations
list
- list management
-
struct
mipi_dsi_device_info
¶ template for creating a mipi_dsi_device
Definition
struct mipi_dsi_device_info {
char type[DSI_DEV_NAME_SIZE];
u32 channel;
struct device_node *node;
};
Members
type
- DSI peripheral chip type
channel
- DSI virtual channel assigned to peripheral
node
- pointer to OF device node or NULL
Description
This is populated and passed to mipi_dsi_device_new to create a new DSI device
-
struct
mipi_dsi_device
¶ DSI peripheral device
Definition
struct mipi_dsi_device {
struct mipi_dsi_host *host;
struct device dev;
char name[DSI_DEV_NAME_SIZE];
unsigned int channel;
unsigned int lanes;
enum mipi_dsi_pixel_format format;
unsigned long mode_flags;
unsigned long hs_rate;
unsigned long lp_rate;
};
Members
host
- DSI host for this peripheral
dev
- driver model device node for this peripheral
name
- DSI peripheral chip type
channel
- virtual channel assigned to the peripheral
lanes
- number of active data lanes
format
- pixel format for video mode
mode_flags
- DSI operation mode related flags
hs_rate
- maximum lane frequency for high speed mode in hertz, this should be set to the real limits of the hardware, zero is only accepted for legacy drivers
lp_rate
- maximum lane frequency for low power mode in hertz, this should be set to the real limits of the hardware, zero is only accepted for legacy drivers
-
int
mipi_dsi_pixel_format_to_bpp
(enum mipi_dsi_pixel_format fmt)¶ obtain the number of bits per pixel for any given pixel format defined by the MIPI DSI specification
Parameters
enum mipi_dsi_pixel_format fmt
- MIPI DSI pixel format
Return
The number of bits per pixel of the given pixel format.
-
enum
mipi_dsi_dcs_tear_mode
¶ Tearing Effect Output Line mode
Constants
MIPI_DSI_DCS_TEAR_MODE_VBLANK
- the TE output line consists of V-Blanking information only
MIPI_DSI_DCS_TEAR_MODE_VHBLANK
- the TE output line consists of both V-Blanking and H-Blanking information
-
struct
mipi_dsi_driver
¶ DSI driver
Definition
struct mipi_dsi_driver {
struct device_driver driver;
int(*probe)(struct mipi_dsi_device *dsi);
int(*remove)(struct mipi_dsi_device *dsi);
void (*shutdown)(struct mipi_dsi_device *dsi);
};
Members
driver
- device driver model driver
probe
- callback for device binding
remove
- callback for device unbinding
shutdown
- called at shutdown time to quiesce the device
-
struct mipi_dsi_device *
of_find_mipi_dsi_device_by_node
(struct device_node *np)¶ find the MIPI DSI device matching a device tree node
Parameters
struct device_node *np
- device tree node
Return
- A pointer to the MIPI DSI device corresponding to np or NULL if no
- such device exists (or has not been registered yet).
-
struct mipi_dsi_device *
mipi_dsi_device_register_full
(struct mipi_dsi_host *host, const struct mipi_dsi_device_info *info)¶ create a MIPI DSI device
Parameters
struct mipi_dsi_host *host
- DSI host to which this device is connected
const struct mipi_dsi_device_info *info
- pointer to template containing DSI device information
Description
Create a MIPI DSI device by using the device information provided by mipi_dsi_device_info template
Return
A pointer to the newly created MIPI DSI device, or, a pointer encoded with an error
-
void
mipi_dsi_device_unregister
(struct mipi_dsi_device *dsi)¶ unregister MIPI DSI device
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
-
struct mipi_dsi_host *
of_find_mipi_dsi_host_by_node
(struct device_node *node)¶ find the MIPI DSI host matching a device tree node
Parameters
struct device_node *node
- device tree node
Return
A pointer to the MIPI DSI host corresponding to node or NULL if no such device exists (or has not been registered yet).
-
int
mipi_dsi_attach
(struct mipi_dsi_device *dsi)¶ attach a DSI device to its DSI host
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral
-
int
mipi_dsi_detach
(struct mipi_dsi_device *dsi)¶ detach a DSI device from its DSI host
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral
-
bool
mipi_dsi_packet_format_is_short
(u8 type)¶ check if a packet is of the short format
Parameters
u8 type
- MIPI DSI data type of the packet
Return
true if the packet for the given data type is a short packet, false otherwise.
-
bool
mipi_dsi_packet_format_is_long
(u8 type)¶ check if a packet is of the long format
Parameters
u8 type
- MIPI DSI data type of the packet
Return
true if the packet for the given data type is a long packet, false otherwise.
-
int
mipi_dsi_create_packet
(struct mipi_dsi_packet *packet, const struct mipi_dsi_msg *msg)¶ create a packet from a message according to the DSI protocol
Parameters
struct mipi_dsi_packet *packet
- pointer to a DSI packet structure
const struct mipi_dsi_msg *msg
- message to translate into a packet
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_shutdown_peripheral
(struct mipi_dsi_device *dsi)¶ sends a Shutdown Peripheral command
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_turn_on_peripheral
(struct mipi_dsi_device *dsi)¶ sends a Turn On Peripheral command
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
Return
0 on success or a negative error code on failure.
-
ssize_t
mipi_dsi_compression_mode
(struct mipi_dsi_device *dsi, bool enable)¶ enable/disable DSC on the peripheral
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
bool enable
- Whether to enable or disable the DSC
Description
Enable or disable Display Stream Compression on the peripheral using the default Picture Parameter Set and VESA DSC 1.1 algorithm.
Return
0 on success or a negative error code on failure.
-
ssize_t
mipi_dsi_picture_parameter_set
(struct mipi_dsi_device *dsi, const struct drm_dsc_picture_parameter_set *pps)¶ transmit the DSC PPS to the peripheral
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
const struct drm_dsc_picture_parameter_set *pps
- VESA DSC 1.1 Picture Parameter Set
Description
Transmit the VESA DSC 1.1 Picture Parameter Set to the peripheral.
Return
0 on success or a negative error code on failure.
-
ssize_t
mipi_dsi_generic_write
(struct mipi_dsi_device *dsi, const void *payload, size_t size)¶ transmit data using a generic write packet
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
const void *payload
- buffer containing the payload
size_t size
- size of payload buffer
Description
This function will automatically choose the right data type depending on the payload length.
Return
The number of bytes transmitted on success or a negative error code on failure.
-
ssize_t
mipi_dsi_generic_read
(struct mipi_dsi_device *dsi, const void *params, size_t num_params, void *data, size_t size)¶ receive data using a generic read packet
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
const void *params
- buffer containing the request parameters
size_t num_params
- number of request parameters
void *data
- buffer in which to return the received data
size_t size
- size of receive buffer
Description
This function will automatically choose the right data type depending on the number of parameters passed in.
Return
The number of bytes successfully read or a negative error code on failure.
-
ssize_t
mipi_dsi_dcs_write_buffer
(struct mipi_dsi_device *dsi, const void *data, size_t len)¶ transmit a DCS command with payload
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
const void *data
- buffer containing data to be transmitted
size_t len
- size of transmission buffer
Description
This function will automatically choose the right data type depending on the command payload length.
Return
The number of bytes successfully transmitted or a negative error code on failure.
-
ssize_t
mipi_dsi_dcs_write
(struct mipi_dsi_device *dsi, u8 cmd, const void *data, size_t len)¶ send DCS write command
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
u8 cmd
- DCS command
const void *data
- buffer containing the command payload
size_t len
- command payload length
Description
This function will automatically choose the right data type depending on the command payload length.
Return
The number of bytes successfully transmitted or a negative error code on failure.
-
ssize_t
mipi_dsi_dcs_read
(struct mipi_dsi_device *dsi, u8 cmd, void *data, size_t len)¶ send DCS read request command
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
u8 cmd
- DCS command
void *data
- buffer in which to receive data
size_t len
- size of receive buffer
Return
The number of bytes read or a negative error code on failure.
-
int
mipi_dsi_dcs_nop
(struct mipi_dsi_device *dsi)¶ send DCS nop packet
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_dcs_soft_reset
(struct mipi_dsi_device *dsi)¶ perform a software reset of the display module
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_dcs_get_power_mode
(struct mipi_dsi_device *dsi, u8 *mode)¶ query the display module’s current power mode
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
u8 *mode
- return location for the current power mode
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_dcs_get_pixel_format
(struct mipi_dsi_device *dsi, u8 *format)¶ gets the pixel format for the RGB image data used by the interface
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
u8 *format
- return location for the pixel format
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_dcs_enter_sleep_mode
(struct mipi_dsi_device *dsi)¶ disable all unnecessary blocks inside the display module except interface communication
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_dcs_exit_sleep_mode
(struct mipi_dsi_device *dsi)¶ enable all blocks inside the display module
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_dcs_set_display_off
(struct mipi_dsi_device *dsi)¶ stop displaying the image data on the display device
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_dcs_set_display_on
(struct mipi_dsi_device *dsi)¶ start displaying the image data on the display device
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
Return
0 on success or a negative error code on failure
-
int
mipi_dsi_dcs_set_column_address
(struct mipi_dsi_device *dsi, u16 start, u16 end)¶ define the column extent of the frame memory accessed by the host processor
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
u16 start
- first column of frame memory
u16 end
- last column of frame memory
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_dcs_set_page_address
(struct mipi_dsi_device *dsi, u16 start, u16 end)¶ define the page extent of the frame memory accessed by the host processor
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
u16 start
- first page of frame memory
u16 end
- last page of frame memory
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_dcs_set_tear_off
(struct mipi_dsi_device *dsi)¶ turn off the display module’s Tearing Effect output signal on the TE signal line
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
Return
0 on success or a negative error code on failure
-
int
mipi_dsi_dcs_set_tear_on
(struct mipi_dsi_device *dsi, enum mipi_dsi_dcs_tear_mode mode)¶ turn on the display module’s Tearing Effect output signal on the TE signal line.
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
enum mipi_dsi_dcs_tear_mode mode
- the Tearing Effect Output Line mode
Return
0 on success or a negative error code on failure
-
int
mipi_dsi_dcs_set_pixel_format
(struct mipi_dsi_device *dsi, u8 format)¶ sets the pixel format for the RGB image data used by the interface
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
u8 format
- pixel format
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_dcs_set_tear_scanline
(struct mipi_dsi_device *dsi, u16 scanline)¶ set the scanline to use as trigger for the Tearing Effect output signal of the display module
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
u16 scanline
- scanline to use as trigger
Return
0 on success or a negative error code on failure
-
int
mipi_dsi_dcs_set_display_brightness
(struct mipi_dsi_device *dsi, u16 brightness)¶ sets the brightness value of the display
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
u16 brightness
- brightness value
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_dcs_get_display_brightness
(struct mipi_dsi_device *dsi, u16 *brightness)¶ gets the current brightness value of the display
Parameters
struct mipi_dsi_device *dsi
- DSI peripheral device
u16 *brightness
- brightness value
Return
0 on success or a negative error code on failure.
-
int
mipi_dsi_driver_register_full
(struct mipi_dsi_driver *drv, struct module *owner)¶ register a driver for DSI devices
Parameters
struct mipi_dsi_driver *drv
- DSI driver structure
struct module *owner
- owner module
Return
0 on success or a negative error code on failure.
-
void
mipi_dsi_driver_unregister
(struct mipi_dsi_driver *drv)¶ unregister a driver for DSI devices
Parameters
struct mipi_dsi_driver *drv
- DSI driver structure
Return
0 on success or a negative error code on failure.
Display Stream Compression Helper Functions Reference¶
VESA specification for DP 1.4 adds a new feature called Display Stream Compression (DSC) used to compress the pixel bits before sending it on DP/eDP/MIPI DSI interface. DSC is required to be enabled so that the existing display interfaces can support high resolutions at higher frames rates uisng the maximum available link capacity of these interfaces.
These functions contain some common logic and helpers to deal with VESA Display Stream Compression standard required for DSC on Display Port/eDP or MIPI display interfaces.
-
struct
drm_dsc_rc_range_parameters
¶ DSC Rate Control range parameters
Definition
struct drm_dsc_rc_range_parameters {
u8 range_min_qp;
u8 range_max_qp;
u8 range_bpg_offset;
};
Members
range_min_qp
- Min Quantization Parameters allowed for this range
range_max_qp
- Max Quantization Parameters allowed for this range
range_bpg_offset
- Bits/group offset to apply to target for this group
Description
This defines different rate control parameters used by the DSC engine to compress the frame.
-
struct
drm_dsc_config
¶ Parameters required to configure DSC
Definition
struct drm_dsc_config {
u8 line_buf_depth;
u8 bits_per_component;
bool convert_rgb;
u8 slice_count;
u16 slice_width;
u16 slice_height;
bool simple_422;
u16 pic_width;
u16 pic_height;
u8 rc_tgt_offset_high;
u8 rc_tgt_offset_low;
u16 bits_per_pixel;
u8 rc_edge_factor;
u8 rc_quant_incr_limit1;
u8 rc_quant_incr_limit0;
u16 initial_xmit_delay;
u16 initial_dec_delay;
bool block_pred_enable;
u8 first_line_bpg_offset;
u16 initial_offset;
u16 rc_buf_thresh[DSC_NUM_BUF_RANGES - 1];
struct drm_dsc_rc_range_parameters rc_range_params[DSC_NUM_BUF_RANGES];
u16 rc_model_size;
u8 flatness_min_qp;
u8 flatness_max_qp;
u8 initial_scale_value;
u16 scale_decrement_interval;
u16 scale_increment_interval;
u16 nfl_bpg_offset;
u16 slice_bpg_offset;
u16 final_offset;
bool vbr_enable;
u8 mux_word_size;
u16 slice_chunk_size;
u16 rc_bits;
u8 dsc_version_minor;
u8 dsc_version_major;
bool native_422;
bool native_420;
u8 second_line_bpg_offset;
u16 nsl_bpg_offset;
u16 second_line_offset_adj;
};
Members
line_buf_depth
- Bits per component for previous reconstructed line buffer
bits_per_component
- Bits per component to code (8/10/12)
convert_rgb
- Flag to indicate if RGB - YCoCg conversion is needed True if RGB input, False if YCoCg input
slice_count
- Number fo slices per line used by the DSC encoder
slice_width
- Width of each slice in pixels
slice_height
- Slice height in pixels
simple_422
- True if simple 4_2_2 mode is enabled else False
pic_width
- Width of the input display frame in pixels
pic_height
- Vertical height of the input display frame
rc_tgt_offset_high
- Offset to bits/group used by RC to determine QP adjustment
rc_tgt_offset_low
- Offset to bits/group used by RC to determine QP adjustment
bits_per_pixel
- Target bits per pixel with 4 fractional bits, bits_per_pixel << 4
rc_edge_factor
- Factor to determine if an edge is present based on the bits produced
rc_quant_incr_limit1
- Slow down incrementing once the range reaches this value
rc_quant_incr_limit0
- Slow down incrementing once the range reaches this value
initial_xmit_delay
- Number of pixels to delay the initial transmission
initial_dec_delay
- Initial decoder delay, number of pixel times that the decoder accumulates data in its rate buffer before starting to decode and output pixels.
block_pred_enable
- True if block prediction is used to code any groups within the picture. False if BP not used
first_line_bpg_offset
- Number of additional bits allocated for each group on the first line of slice.
initial_offset
- Value to use for RC model offset at slice start
rc_buf_thresh
- Thresholds defining each of the buffer ranges
rc_range_params
- Parameters for each of the RC ranges defined in
struct drm_dsc_rc_range_parameters
rc_model_size
- Total size of RC model
flatness_min_qp
- Minimum QP where flatness information is sent
flatness_max_qp
- Maximum QP where flatness information is sent
initial_scale_value
- Initial value for the scale factor
scale_decrement_interval
- Specifies number of group times between decrementing the scale factor at beginning of a slice.
scale_increment_interval
- Number of group times between incrementing the scale factor value used at the beginning of a slice.
nfl_bpg_offset
- Non first line BPG offset to be used
slice_bpg_offset
- BPG offset used to enforce slice bit
final_offset
- Final RC linear transformation offset value
vbr_enable
- True if VBR mode is enabled, false if disabled
mux_word_size
- Mux word size (in bits) for SSM mode
slice_chunk_size
- The (max) size in bytes of the “chunks” that are used in slice multiplexing.
rc_bits
- Rate control buffer size in bits
dsc_version_minor
- DSC minor version
dsc_version_major
- DSC major version
native_422
- True if Native 4:2:2 supported, else false
native_420
- True if Native 4:2:0 supported else false.
second_line_bpg_offset
- Additional bits/grp for seconnd line of slice for native 4:2:0
nsl_bpg_offset
- Num of bits deallocated for each grp that is not in second line of slice
second_line_offset_adj
- Offset adjustment for second line in Native 4:2:0 mode
Description
Driver populates this structure with all the parameters required to configure the display stream compression on the source.
-
struct
drm_dsc_picture_parameter_set
¶ Represents 128 bytes of Picture Parameter Set
Definition
struct drm_dsc_picture_parameter_set {
u8 dsc_version;
u8 pps_identifier;
u8 pps_reserved;
u8 pps_3;
u8 pps_4;
u8 bits_per_pixel_low;
__be16 pic_height;
__be16 pic_width;
__be16 slice_height;
__be16 slice_width;
__be16 chunk_size;
u8 initial_xmit_delay_high;
u8 initial_xmit_delay_low;
__be16 initial_dec_delay;
u8 pps20_reserved;
u8 initial_scale_value;
__be16 scale_increment_interval;
u8 scale_decrement_interval_high;
u8 scale_decrement_interval_low;
u8 pps26_reserved;
u8 first_line_bpg_offset;
__be16 nfl_bpg_offset;
__be16 slice_bpg_offset;
__be16 initial_offset;
__be16 final_offset;
u8 flatness_min_qp;
u8 flatness_max_qp;
__be16 rc_model_size;
u8 rc_edge_factor;
u8 rc_quant_incr_limit0;
u8 rc_quant_incr_limit1;
u8 rc_tgt_offset;
u8 rc_buf_thresh[DSC_NUM_BUF_RANGES - 1];
__be16 rc_range_parameters[DSC_NUM_BUF_RANGES];
u8 native_422_420;
u8 second_line_bpg_offset;
__be16 nsl_bpg_offset;
__be16 second_line_offset_adj;
u32 pps_long_94_reserved;
u32 pps_long_98_reserved;
u32 pps_long_102_reserved;
u32 pps_long_106_reserved;
u32 pps_long_110_reserved;
u32 pps_long_114_reserved;
u32 pps_long_118_reserved;
u32 pps_long_122_reserved;
__be16 pps_short_126_reserved;
};
Members
dsc_version
- PPS0[3:0] - dsc_version_minor: Contains Minor version of DSC PPS0[7:4] - dsc_version_major: Contains major version of DSC
pps_identifier
- PPS1[7:0] - Application specific identifier that can be used to differentiate between different PPS tables.
pps_reserved
- PPS2[7:0]- RESERVED Byte
pps_3
- PPS3[3:0] - linebuf_depth: Contains linebuffer bit depth used to generate the bitstream. (0x0 - 16 bits for DSC 1.2, 0x8 - 8 bits, 0xA - 10 bits, 0xB - 11 bits, 0xC - 12 bits, 0xD - 13 bits, 0xE - 14 bits for DSC1.2, 0xF - 14 bits for DSC 1.2. PPS3[7:4] - bits_per_component: Bits per component for the original pixels of the encoded picture. 0x0 = 16bpc (allowed only when dsc_version_minor = 0x2) 0x8 = 8bpc, 0xA = 10bpc, 0xC = 12bpc, 0xE = 14bpc (also allowed only when dsc_minor_version = 0x2)
pps_4
- PPS4[1:0] -These are the most significant 2 bits of compressed BPP bits_per_pixel[9:0] syntax element. PPS4[2] - vbr_enable: 0 = VBR disabled, 1 = VBR enabled PPS4[3] - simple_422: Indicates if decoder drops samples to reconstruct the 4:2:2 picture. PPS4[4] - Convert_rgb: Indicates if DSC color space conversion is active. PPS4[5] - blobk_pred_enable: Indicates if BP is used to code any groups in picture PPS4[7:6] - Reseved bits
bits_per_pixel_low
- PPS5[7:0] - This indicates the lower significant 8 bits of the compressed BPP bits_per_pixel[9:0] element.
pic_height
- PPS6[7:0], PPS7[7:0] -pic_height: Specifies the number of pixel rows within the raster.
pic_width
- PPS8[7:0], PPS9[7:0] - pic_width: Number of pixel columns within the raster.
slice_height
- PPS10[7:0], PPS11[7:0] - Slice height in units of pixels.
slice_width
- PPS12[7:0], PPS13[7:0] - Slice width in terms of pixels.
chunk_size
- PPS14[7:0], PPS15[7:0] - Size in units of bytes of the chunks that are used for slice multiplexing.
initial_xmit_delay_high
- PPS16[1:0] - Most Significant two bits of initial transmission delay. It specifies the number of pixel times that the encoder waits before transmitting data from its rate buffer. PPS16[7:2] - Reserved
initial_xmit_delay_low
- PPS17[7:0] - Least significant 8 bits of initial transmission delay.
initial_dec_delay
- PPS18[7:0], PPS19[7:0] - Initial decoding delay which is the number of pixel times that the decoder accumulates data in its rate buffer before starting to decode and output pixels.
pps20_reserved
- PPS20[7:0] - Reserved
initial_scale_value
- PPS21[5:0] - Initial rcXformScale factor used at beginning of a slice. PPS21[7:6] - Reserved
scale_increment_interval
- PPS22[7:0], PPS23[7:0] - Number of group times between incrementing the rcXformScale factor at end of a slice.
scale_decrement_interval_high
- PPS24[3:0] - Higher 4 bits indicating number of group times between decrementing the rcXformScale factor at beginning of a slice. PPS24[7:4] - Reserved
scale_decrement_interval_low
- PPS25[7:0] - Lower 8 bits of scale decrement interval
pps26_reserved
- PPS26[7:0]
first_line_bpg_offset
- PPS27[4:0] - Number of additional bits that are allocated for each group on first line of a slice. PPS27[7:5] - Reserved
nfl_bpg_offset
- PPS28[7:0], PPS29[7:0] - Number of bits including frac bits deallocated for each group for groups after the first line of slice.
slice_bpg_offset
- PPS30, PPS31[7:0] - Number of bits that are deallocated for each group to enforce the slice constraint.
initial_offset
- PPS32,33[7:0] - Initial value for rcXformOffset
final_offset
- PPS34,35[7:0] - Maximum end-of-slice value for rcXformOffset
flatness_min_qp
- PPS36[4:0] - Minimum QP at which flatness is signaled and flatness QP adjustment is made. PPS36[7:5] - Reserved
flatness_max_qp
- PPS37[4:0] - Max QP at which flatness is signalled and the flatness adjustment is made. PPS37[7:5] - Reserved
rc_model_size
- PPS38,39[7:0] - Number of bits within RC Model.
rc_edge_factor
- PPS40[3:0] - Ratio of current activity vs, previous activity to determine presence of edge. PPS40[7:4] - Reserved
rc_quant_incr_limit0
- PPS41[4:0] - QP threshold used in short term RC PPS41[7:5] - Reserved
rc_quant_incr_limit1
- PPS42[4:0] - QP threshold used in short term RC PPS42[7:5] - Reserved
rc_tgt_offset
- PPS43[3:0] - Lower end of the variability range around the target bits per group that is allowed by short term RC. PPS43[7:4]- Upper end of the variability range around the target bits per group that i allowed by short term rc.
rc_buf_thresh
- PPS44[7:0] - PPS57[7:0] - Specifies the thresholds in RC model for the 15 ranges defined by 14 thresholds.
rc_range_parameters
- PPS58[7:0] - PPS87[7:0] Parameters that correspond to each of the 15 ranges.
native_422_420
- PPS88[0] - 0 = Native 4:2:2 not used 1 = Native 4:2:2 used PPS88[1] - 0 = Native 4:2:0 not use 1 = Native 4:2:0 used PPS88[7:2] - Reserved 6 bits
second_line_bpg_offset
- PPS89[4:0] - Additional bits/group budget for the second line of a slice in Native 4:2:0 mode. Set to 0 if DSC minor version is 1 or native420 is 0. PPS89[7:5] - Reserved
nsl_bpg_offset
- PPS90[7:0], PPS91[7:0] - Number of bits that are deallocated for each group that is not in the second line of a slice.
second_line_offset_adj
- PPS92[7:0], PPS93[7:0] - Used as offset adjustment for the second line in Native 4:2:0 mode.
pps_long_94_reserved
- PPS 94, 95, 96, 97 - Reserved
pps_long_98_reserved
- PPS 98, 99, 100, 101 - Reserved
pps_long_102_reserved
- PPS 102, 103, 104, 105 - Reserved
pps_long_106_reserved
- PPS 106, 107, 108, 109 - reserved
pps_long_110_reserved
- PPS 110, 111, 112, 113 - reserved
pps_long_114_reserved
- PPS 114 - 117 - reserved
pps_long_118_reserved
- PPS 118 - 121 - reserved
pps_long_122_reserved
- PPS 122- 125 - reserved
pps_short_126_reserved
- PPS 126, 127 - reserved
Description
The VESA DSC standard defines picture parameter set (PPS) which display stream compression encoders must communicate to decoders. The PPS is encapsulated in 128 bytes (PPS 0 through PPS 127). The fields in this structure are as per Table 4.1 in Vesa DSC specification v1.1/v1.2. The PPS fields that span over more than a byte should be stored in Big Endian format.
-
struct
drm_dsc_pps_infoframe
¶ DSC infoframe carrying the Picture Parameter Set Metadata
Definition
struct drm_dsc_pps_infoframe {
struct dp_sdp_header pps_header;
struct drm_dsc_picture_parameter_set pps_payload;
};
Members
pps_header
- Header for PPS as per DP SDP header format of type
struct dp_sdp_header
pps_payload
- PPS payload fields as per DSC specification Table 4-1
as represented in
struct drm_dsc_picture_parameter_set
Description
This structure represents the DSC PPS infoframe required to send the Picture
Parameter Set metadata required before enabling VESA Display Stream
Compression. This is based on the DP Secondary Data Packet structure and
comprises of SDP Header as defined struct dp_sdp_header
in drm_dp_helper.h
and PPS payload defined in struct drm_dsc_picture_parameter_set
.
-
void
drm_dsc_dp_pps_header_init
(struct dp_sdp_header *pps_header)¶ Initializes the PPS Header for DisplayPort as per the DP 1.4 spec.
Parameters
struct dp_sdp_header *pps_header
- Secondary data packet header for DSC Picture
Parameter Set as defined in
struct dp_sdp_header
Description
DP 1.4 spec defines the secondary data packet for sending the
picture parameter infoframes from the source to the sink.
This function populates the SDP header defined in
struct dp_sdp_header
.
-
void
drm_dsc_pps_payload_pack
(struct drm_dsc_picture_parameter_set *pps_payload, const struct drm_dsc_config *dsc_cfg)¶ Populates the DSC PPS
Parameters
struct drm_dsc_picture_parameter_set *pps_payload
- Bitwise struct for DSC Picture Parameter Set. This is defined
by
struct drm_dsc_picture_parameter_set
const struct drm_dsc_config *dsc_cfg
- DSC Configuration data filled by driver as defined by
struct drm_dsc_config
Description
DSC source device sends a picture parameter set (PPS) containing the information required by the sink to decode the compressed frame. Driver populates the DSC PPS struct using the DSC configuration parameters in the order expected by the DSC Display Sink device. For the DSC, the sink device expects the PPS payload in big endian format for fields that span more than 1 byte.
-
int
drm_dsc_compute_rc_parameters
(struct drm_dsc_config *vdsc_cfg)¶ Write rate control parameters to the dsc configuration defined in
struct drm_dsc_config
in accordance with the DSC 1.2 specification. Some configuration fields must be present beforehand.
Parameters
struct drm_dsc_config *vdsc_cfg
- DSC Configuration data partially filled by driver
Output Probing Helper Functions Reference¶
This library provides some helper code for output probing. It provides an
implementation of the core drm_connector_funcs.fill_modes
interface with
drm_helper_probe_single_connector_modes()
.
It also provides support for polling connectors with a work item and for generic hotplug interrupt handling where the driver doesn’t or cannot keep track of a per-connector hpd interrupt.
This helper library can be used independently of the modeset helper library. Drivers can also overwrite different parts e.g. use their own hotplug handling code to avoid probing unrelated outputs.
The probe helpers share the function table structures with other display
helper libraries. See struct drm_connector_helper_funcs
for the details.
-
void
drm_kms_helper_poll_enable
(struct drm_device *dev)¶ re-enable output polling.
Parameters
struct drm_device *dev
- drm_device
Description
This function re-enables the output polling work, after it has been
temporarily disabled using drm_kms_helper_poll_disable()
, for example over
suspend/resume.
Drivers can call this helper from their device resume implementation. It is not an error to call this even when output polling isn’t enabled.
Note that calls to enable and disable polling must be strictly ordered, which is automatically the case when they’re only call from suspend/resume callbacks.
-
int
drm_helper_probe_detect
(struct drm_connector *connector, struct drm_modeset_acquire_ctx *ctx, bool force)¶ probe connector status
Parameters
struct drm_connector *connector
- connector to probe
struct drm_modeset_acquire_ctx *ctx
- acquire_ctx, or NULL to let this function handle locking.
bool force
- Whether destructive probe operations should be performed.
Description
This function calls the detect callbacks of the connector.
This function returns drm_connector_status
, or
if ctx is set, it might also return -EDEADLK.
-
int
drm_helper_probe_single_connector_modes
(struct drm_connector *connector, uint32_t maxX, uint32_t maxY)¶ get complete set of display modes
Parameters
struct drm_connector *connector
- connector to probe
uint32_t maxX
- max width for modes
uint32_t maxY
- max height for modes
Description
Based on the helper callbacks implemented by connector in struct
drm_connector_helper_funcs
try to detect all valid modes. Modes will first
be added to the connector’s probed_modes list, then culled (based on validity
and the maxX, maxY parameters) and put into the normal modes list.
Intended to be used as a generic implementation of the
drm_connector_funcs.fill_modes()
vfunc for drivers that use the CRTC helpers
for output mode filtering and detection.
The basic procedure is as follows
All modes currently on the connector’s modes list are marked as stale
New modes are added to the connector’s probed_modes list with
drm_mode_probed_add()
. New modes start their life with status as OK. Modes are added from a single source using the following priority order.drm_connector_helper_funcs.get_modes
vfunc- if the connector status is connector_status_connected, standard
VESA DMT modes up to 1024x768 are automatically added
(
drm_add_modes_noedid()
)
Finally modes specified via the kernel command line (video=…) are added in addition to what the earlier probes produced (drm_helper_probe_add_cmdline_mode()). These modes are generated using the VESA GTF/CVT formulas.
Modes are moved from the probed_modes list to the modes list. Potential duplicates are merged together (see
drm_connector_list_update()
). After this step the probed_modes list will be empty again.Any non-stale mode on the modes list then undergoes validation
- drm_mode_validate_basic() performs basic sanity checks
drm_mode_validate_size()
filters out modes larger than maxX and maxY (if specified)- drm_mode_validate_flag() checks the modes against basic connector capabilities (interlace_allowed,doublescan_allowed,stereo_allowed)
- the optional
drm_connector_helper_funcs.mode_valid
ordrm_connector_helper_funcs.mode_valid_ctx
helpers can perform driver and/or sink specific checks - the optional
drm_crtc_helper_funcs.mode_valid
,drm_bridge_funcs.mode_valid
anddrm_encoder_helper_funcs.mode_valid
helpers can perform driver and/or source specific checks which are also enforced by the modeset/atomic helpers
Any mode whose status is not OK is pruned from the connector’s modes list, accompanied by a debug message indicating the reason for the mode’s rejection (see
drm_mode_prune_invalid()
).
Return
The number of modes found on connector.
-
void
drm_kms_helper_hotplug_event
(struct drm_device *dev)¶ fire off KMS hotplug events
Parameters
struct drm_device *dev
- drm_device whose connector state changed
Description
This function fires off the uevent for userspace and also calls the output_poll_changed function, which is most commonly used to inform the fbdev emulation code and allow it to update the fbcon output configuration.
Drivers should call this from their hotplug handling code when a change is
detected. Note that this function does not do any output detection of its
own, like drm_helper_hpd_irq_event()
does - this is assumed to be done by the
driver already.
This function must be called from process context with no mode setting locks held.
-
bool
drm_kms_helper_is_poll_worker
(void)¶ is
current
task an output poll worker?
Parameters
void
- no arguments
Description
Determine if current
task is an output poll worker. This can be used
to select distinct code paths for output polling versus other contexts.
One use case is to avoid a deadlock between the output poll worker and
the autosuspend worker wherein the latter waits for polling to finish
upon calling drm_kms_helper_poll_disable()
, while the former waits for
runtime suspend to finish upon calling pm_runtime_get_sync() in a
connector ->detect hook.
-
void
drm_kms_helper_poll_disable
(struct drm_device *dev)¶ disable output polling
Parameters
struct drm_device *dev
- drm_device
Description
This function disables the output polling work.
Drivers can call this helper from their device suspend implementation. It is
not an error to call this even when output polling isn’t enabled or already
disabled. Polling is re-enabled by calling drm_kms_helper_poll_enable()
.
Note that calls to enable and disable polling must be strictly ordered, which is automatically the case when they’re only call from suspend/resume callbacks.
-
void
drm_kms_helper_poll_init
(struct drm_device *dev)¶ initialize and enable output polling
Parameters
struct drm_device *dev
- drm_device
Description
This function intializes and then also enables output polling support for dev. Drivers which do not have reliable hotplug support in hardware can use this helper infrastructure to regularly poll such connectors for changes in their connection state.
Drivers can control which connectors are polled by setting the DRM_CONNECTOR_POLL_CONNECT and DRM_CONNECTOR_POLL_DISCONNECT flags. On connectors where probing live outputs can result in visual distortion drivers should not set the DRM_CONNECTOR_POLL_DISCONNECT flag to avoid this. Connectors which have no flag or only DRM_CONNECTOR_POLL_HPD set are completely ignored by the polling logic.
Note that a connector can be both polled and probed from the hotplug handler, in case the hotplug interrupt is known to be unreliable.
-
void
drm_kms_helper_poll_fini
(struct drm_device *dev)¶ disable output polling and clean it up
Parameters
struct drm_device *dev
- drm_device
-
bool
drm_helper_hpd_irq_event
(struct drm_device *dev)¶ hotplug processing
Parameters
struct drm_device *dev
- drm_device
Description
Drivers can use this helper function to run a detect cycle on all connectors
which have the DRM_CONNECTOR_POLL_HPD flag set in their polled
member. All
other connectors are ignored, which is useful to avoid reprobing fixed
panels.
This helper function is useful for drivers which can’t or don’t track hotplug interrupts for each connector.
Drivers which support hotplug interrupts for each connector individually and
which have a more fine-grained detect logic should bypass this code and
directly call drm_kms_helper_hotplug_event()
in case the connector state
changed.
This function must be called from process context with no mode setting locks held.
Note that a connector can be both polled and probed from the hotplug handler, in case the hotplug interrupt is known to be unreliable.
EDID Helper Functions Reference¶
-
int
drm_eld_mnl
(const uint8_t *eld)¶ Get ELD monitor name length in bytes.
Parameters
const uint8_t *eld
- pointer to an eld memory structure with mnl set
-
const uint8_t *
drm_eld_sad
(const uint8_t *eld)¶ Get ELD SAD structures.
Parameters
const uint8_t *eld
- pointer to an eld memory structure with sad_count set
-
int
drm_eld_sad_count
(const uint8_t *eld)¶ Get ELD SAD count.
Parameters
const uint8_t *eld
- pointer to an eld memory structure with sad_count set
-
int
drm_eld_calc_baseline_block_size
(const uint8_t *eld)¶ Calculate baseline block size in bytes
Parameters
const uint8_t *eld
- pointer to an eld memory structure with mnl and sad_count set
Description
This is a helper for determining the payload size of the baseline block, in bytes, for e.g. setting the Baseline_ELD_Len field in the ELD header block.
-
int
drm_eld_size
(const uint8_t *eld)¶ Get ELD size in bytes
Parameters
const uint8_t *eld
- pointer to a complete eld memory structure
Description
The returned value does not include the vendor block. It’s vendor specific,
and comprises of the remaining bytes in the ELD memory buffer after
drm_eld_size()
bytes of header and baseline block.
The returned value is guaranteed to be a multiple of 4.
-
u8
drm_eld_get_spk_alloc
(const uint8_t *eld)¶ Get speaker allocation
Parameters
const uint8_t *eld
- pointer to an ELD memory structure
Description
The returned value is the speakers mask. User has to use DRM_ELD_SPEAKER
field definitions to identify speakers.
-
u8
drm_eld_get_conn_type
(const uint8_t *eld)¶ Get device type hdmi/dp connected
Parameters
const uint8_t *eld
- pointer to an ELD memory structure
Description
The caller need to use DRM_ELD_CONN_TYPE_HDMI
or DRM_ELD_CONN_TYPE_DP
to
identify the display type connected.
-
int
drm_edid_header_is_valid
(const u8 *raw_edid)¶ sanity check the header of the base EDID block
Parameters
const u8 *raw_edid
- pointer to raw base EDID block
Description
Sanity check the header of the base EDID block.
Return
8 if the header is perfect, down to 0 if it’s totally wrong.
-
bool
drm_edid_are_equal
(const struct edid *edid1, const struct edid *edid2)¶ compare two edid blobs.
Parameters
const struct edid *edid1
- pointer to first blob
const struct edid *edid2
- pointer to second blob This helper can be used during probing to determine if edid had changed.
-
bool
drm_edid_block_valid
(u8 *raw_edid, int block, bool print_bad_edid, bool *edid_corrupt)¶ Sanity check the EDID block (base or extension)
Parameters
u8 *raw_edid
- pointer to raw EDID block
int block
- type of block to validate (0 for base, extension otherwise)
bool print_bad_edid
- if true, dump bad EDID blocks to the console
bool *edid_corrupt
- if true, the header or checksum is invalid
Description
Validate a base or extension EDID block and optionally dump bad blocks to the console.
Return
True if the block is valid, false otherwise.
-
bool
drm_edid_is_valid
(struct edid *edid)¶ sanity check EDID data
Parameters
struct edid *edid
- EDID data
Description
Sanity-check an entire EDID record (including extensions)
Return
True if the EDID data is valid, false otherwise.
-
int
drm_add_override_edid_modes
(struct drm_connector *connector)¶ add modes from override/firmware EDID
Parameters
struct drm_connector *connector
- connector we’re probing
Description
Add modes from the override/firmware EDID, if available. Only to be used from
drm_helper_probe_single_connector_modes()
as a fallback for when DDC probe
failed during drm_get_edid()
and caused the override/firmware EDID to be
skipped.
Return
The number of modes added or 0 if we couldn’t find any.
-
struct edid *
drm_do_get_edid
(struct drm_connector *connector, int (*get_edid_block)(void *data, u8 *buf, unsigned int block, size_t len), void *data)¶ get EDID data using a custom EDID block read function
Parameters
struct drm_connector *connector
- connector we’re probing
int (*get_edid_block)(void *data, u8 *buf, unsigned int block, size_t len)
- EDID block read function
void *data
- private data passed to the block read function
Description
When the I2C adapter connected to the DDC bus is hidden behind a device that exposes a different interface to read EDID blocks this function can be used to get EDID data using a custom block read function.
As in the general case the DDC bus is accessible by the kernel at the I2C
level, drivers must make all reasonable efforts to expose it as an I2C
adapter and use drm_get_edid()
instead of abusing this function.
The EDID may be overridden using debugfs override_edid or firmare EDID (drm_load_edid_firmware() and drm.edid_firmware parameter), in this priority order. Having either of them bypasses actual EDID reads.
Return
Pointer to valid EDID or NULL if we couldn’t find any.
-
bool
drm_probe_ddc
(struct i2c_adapter *adapter)¶ probe DDC presence
Parameters
struct i2c_adapter *adapter
- I2C adapter to probe
Return
True on success, false on failure.
-
struct edid *
drm_get_edid
(struct drm_connector *connector, struct i2c_adapter *adapter)¶ get EDID data, if available
Parameters
struct drm_connector *connector
- connector we’re probing
struct i2c_adapter *adapter
- I2C adapter to use for DDC
Description
Poke the given I2C channel to grab EDID data if possible. If found, attach it to the connector.
Return
Pointer to valid EDID or NULL if we couldn’t find any.
-
struct edid *
drm_get_edid_switcheroo
(struct drm_connector *connector, struct i2c_adapter *adapter)¶ get EDID data for a vga_switcheroo output
Parameters
struct drm_connector *connector
- connector we’re probing
struct i2c_adapter *adapter
- I2C adapter to use for DDC
Description
Wrapper around drm_get_edid()
for laptops with dual GPUs using one set of
outputs. The wrapper adds the requisite vga_switcheroo calls to temporarily
switch DDC to the GPU which is retrieving EDID.
Return
Pointer to valid EDID or NULL
if we couldn’t find any.
-
struct edid *
drm_edid_duplicate
(const struct edid *edid)¶ duplicate an EDID and the extensions
Parameters
const struct edid *edid
- EDID to duplicate
Return
Pointer to duplicated EDID or NULL on allocation failure.
-
u8
drm_match_cea_mode
(const struct drm_display_mode *to_match)¶ look for a CEA mode matching given mode
Parameters
const struct drm_display_mode *to_match
- display mode
Return
The CEA Video ID (VIC) of the mode or 0 if it isn’t a CEA-861 mode.
-
struct drm_display_mode *
drm_display_mode_from_cea_vic
(struct drm_device *dev, u8 video_code)¶ return a mode for CEA VIC
Parameters
struct drm_device *dev
- DRM device
u8 video_code
- CEA VIC of the mode
Description
Creates a new mode matching the specified CEA VIC.
Return
A new drm_display_mode on success or NULL on failure
-
void
drm_edid_get_monitor_name
(struct edid *edid, char *name, int bufsize)¶ fetch the monitor name from the edid
Parameters
struct edid *edid
- monitor EDID information
char *name
- pointer to a character array to hold the name of the monitor
int bufsize
- The size of the name buffer (should be at least 14 chars.)
-
int
drm_edid_to_sad
(struct edid *edid, struct cea_sad **sads)¶ extracts SADs from EDID
Parameters
struct edid *edid
- EDID to parse
struct cea_sad **sads
- pointer that will be set to the extracted SADs
Description
Looks for CEA EDID block and extracts SADs (Short Audio Descriptors) from it.
Note
The returned pointer needs to be freed using kfree()
.
Return
The number of found SADs or negative number on error.
-
int
drm_edid_to_speaker_allocation
(struct edid *edid, u8 **sadb)¶ extracts Speaker Allocation Data Blocks from EDID
Parameters
struct edid *edid
- EDID to parse
u8 **sadb
- pointer to the speaker block
Description
Looks for CEA EDID block and extracts the Speaker Allocation Data Block from it.
Note
The returned pointer needs to be freed using kfree()
.
Return
The number of found Speaker Allocation Blocks or negative number on error.
-
int
drm_av_sync_delay
(struct drm_connector *connector, const struct drm_display_mode *mode)¶ compute the HDMI/DP sink audio-video sync delay
Parameters
struct drm_connector *connector
- connector associated with the HDMI/DP sink
const struct drm_display_mode *mode
- the display mode
Return
The HDMI/DP sink’s audio-video sync delay in milliseconds or 0 if the sink doesn’t support audio or video.
-
bool
drm_detect_hdmi_monitor
(struct edid *edid)¶ detect whether monitor is HDMI
Parameters
struct edid *edid
- monitor EDID information
Description
Parse the CEA extension according to CEA-861-B.
Drivers that have added the modes parsed from EDID to drm_display_info
should use drm_display_info.is_hdmi
instead of calling this function.
Return
True if the monitor is HDMI, false if not or unknown.
-
bool
drm_detect_monitor_audio
(struct edid *edid)¶ check monitor audio capability
Parameters
struct edid *edid
- EDID block to scan
Description
Monitor should have CEA extension block. If monitor has ‘basic audio’, but no CEA audio blocks, it’s ‘basic audio’ only. If there is any audio extension block and supported audio format, assume at least ‘basic audio’ support, even if ‘basic audio’ is not defined in EDID.
Return
True if the monitor supports audio, false otherwise.
-
enum hdmi_quantization_range
drm_default_rgb_quant_range
(const struct drm_display_mode *mode)¶ default RGB quantization range
Parameters
const struct drm_display_mode *mode
- display mode
Description
Determine the default RGB quantization range for the mode, as specified in CEA-861.
Return
The default RGB quantization range for the mode
-
int
drm_add_edid_modes
(struct drm_connector *connector, struct edid *edid)¶ add modes from EDID data, if available
Parameters
struct drm_connector *connector
- connector we’re probing
struct edid *edid
- EDID data
Description
Add the specified modes to the connector’s mode list. Also fills out the
drm_display_info
structure and ELD in connector with any information which
can be derived from the edid.
Return
The number of modes added or 0 if we couldn’t find any.
-
int
drm_add_modes_noedid
(struct drm_connector *connector, int hdisplay, int vdisplay)¶ add modes for the connectors without EDID
Parameters
struct drm_connector *connector
- connector we’re probing
int hdisplay
- the horizontal display limit
int vdisplay
- the vertical display limit
Description
Add the specified modes to the connector’s mode list. Only when the hdisplay/vdisplay is not beyond the given limit, it will be added.
Return
The number of modes added or 0 if we couldn’t find any.
-
void
drm_set_preferred_mode
(struct drm_connector *connector, int hpref, int vpref)¶ Sets the preferred mode of a connector
Parameters
struct drm_connector *connector
- connector whose mode list should be processed
int hpref
- horizontal resolution of preferred mode
int vpref
- vertical resolution of preferred mode
Description
Marks a mode as preferred if it matches the resolution specified by hpref and vpref.
-
int
drm_hdmi_infoframe_set_hdr_metadata
(struct hdmi_drm_infoframe *frame, const struct drm_connector_state *conn_state)¶ fill an HDMI DRM infoframe with HDR metadata from userspace
Parameters
struct hdmi_drm_infoframe *frame
- HDMI DRM infoframe
const struct drm_connector_state *conn_state
- Connector state containing HDR metadata
Return
0 on success or a negative error code on failure.
-
int
drm_hdmi_avi_infoframe_from_display_mode
(struct hdmi_avi_infoframe *frame, const struct drm_connector *connector, const struct drm_display_mode *mode)¶ fill an HDMI AVI infoframe with data from a DRM display mode
Parameters
struct hdmi_avi_infoframe *frame
- HDMI AVI infoframe
const struct drm_connector *connector
- the connector
const struct drm_display_mode *mode
- DRM display mode
Return
0 on success or a negative error code on failure.
-
void
drm_hdmi_avi_infoframe_colorspace
(struct hdmi_avi_infoframe *frame, const struct drm_connector_state *conn_state)¶ fill the HDMI AVI infoframe colorspace information
Parameters
struct hdmi_avi_infoframe *frame
- HDMI AVI infoframe
const struct drm_connector_state *conn_state
- connector state
-
void
drm_hdmi_avi_infoframe_quant_range
(struct hdmi_avi_infoframe *frame, const struct drm_connector *connector, const struct drm_display_mode *mode, enum hdmi_quantization_range rgb_quant_range)¶ fill the HDMI AVI infoframe quantization range information
Parameters
struct hdmi_avi_infoframe *frame
- HDMI AVI infoframe
const struct drm_connector *connector
- the connector
const struct drm_display_mode *mode
- DRM display mode
enum hdmi_quantization_range rgb_quant_range
- RGB quantization range (Q)
-
void
drm_hdmi_avi_infoframe_bars
(struct hdmi_avi_infoframe *frame, const struct drm_connector_state *conn_state)¶ fill the HDMI AVI infoframe bar information
Parameters
struct hdmi_avi_infoframe *frame
- HDMI AVI infoframe
const struct drm_connector_state *conn_state
- connector state
-
int
drm_hdmi_vendor_infoframe_from_display_mode
(struct hdmi_vendor_infoframe *frame, const struct drm_connector *connector, const struct drm_display_mode *mode)¶ fill an HDMI infoframe with data from a DRM display mode
Parameters
struct hdmi_vendor_infoframe *frame
- HDMI vendor infoframe
const struct drm_connector *connector
- the connector
const struct drm_display_mode *mode
- DRM display mode
Description
Note that there’s is a need to send HDMI vendor infoframes only when using a 4k or stereoscopic 3D mode. So when giving any other mode as input this function will return -EINVAL, error that can be safely ignored.
Return
0 on success or a negative error code on failure.
SCDC Helper Functions Reference¶
Status and Control Data Channel (SCDC) is a mechanism introduced by the HDMI 2.0 specification. It is a point-to-point protocol that allows the HDMI source and HDMI sink to exchange data. The same I2C interface that is used to access EDID serves as the transport mechanism for SCDC.
-
int
drm_scdc_readb
(struct i2c_adapter *adapter, u8 offset, u8 *value)¶ read a single byte from SCDC
Parameters
struct i2c_adapter *adapter
- I2C adapter
u8 offset
- offset of register to read
u8 *value
- return location for the register value
Description
Reads a single byte from SCDC. This is a convenience wrapper around the
drm_scdc_read()
function.
Return
0 on success or a negative error code on failure.
-
int
drm_scdc_writeb
(struct i2c_adapter *adapter, u8 offset, u8 value)¶ write a single byte to SCDC
Parameters
struct i2c_adapter *adapter
- I2C adapter
u8 offset
- offset of register to read
u8 value
- return location for the register value
Description
Writes a single byte to SCDC. This is a convenience wrapper around the
drm_scdc_write()
function.
Return
0 on success or a negative error code on failure.
-
ssize_t
drm_scdc_read
(struct i2c_adapter *adapter, u8 offset, void *buffer, size_t size)¶ read a block of data from SCDC
Parameters
struct i2c_adapter *adapter
- I2C controller
u8 offset
- start offset of block to read
void *buffer
- return location for the block to read
size_t size
- size of the block to read
Description
Reads a block of data from SCDC, starting at a given offset.
Return
0 on success, negative error code on failure.
-
ssize_t
drm_scdc_write
(struct i2c_adapter *adapter, u8 offset, const void *buffer, size_t size)¶ write a block of data to SCDC
Parameters
struct i2c_adapter *adapter
- I2C controller
u8 offset
- start offset of block to write
const void *buffer
- block of data to write
size_t size
- size of the block to write
Description
Writes a block of data to SCDC, starting at a given offset.
Return
0 on success, negative error code on failure.
-
bool
drm_scdc_get_scrambling_status
(struct i2c_adapter *adapter)¶ what is status of scrambling?
Parameters
struct i2c_adapter *adapter
- I2C adapter for DDC channel
Description
Reads the scrambler status over SCDC, and checks the scrambling status.
Return
True if the scrambling is enabled, false otherwise.
-
bool
drm_scdc_set_scrambling
(struct i2c_adapter *adapter, bool enable)¶ enable scrambling
Parameters
struct i2c_adapter *adapter
- I2C adapter for DDC channel
bool enable
- bool to indicate if scrambling is to be enabled/disabled
Description
Writes the TMDS config register over SCDC channel, and: enables scrambling when enable = 1 disables scrambling when enable = 0
Return
True if scrambling is set/reset successfully, false otherwise.
-
bool
drm_scdc_set_high_tmds_clock_ratio
(struct i2c_adapter *adapter, bool set)¶ set TMDS clock ratio
Parameters
struct i2c_adapter *adapter
- I2C adapter for DDC channel
bool set
ret or reset the high clock ratio
- TMDS clock ratio calculations go like this:
TMDS character = 10 bit TMDS encoded value
TMDS character rate = The rate at which TMDS characters are transmitted (Mcsc)
TMDS bit rate = 10x TMDS character rate
- As per the spec:
TMDS clock rate for pixel clock < 340 MHz = 1x the character rate = 1/10 pixel clock rate
TMDS clock rate for pixel clock > 340 MHz = 0.25x the character rate = 1/40 pixel clock rate
- Writes to the TMDS config register over SCDC channel, and:
sets TMDS clock ratio to 1/40 when set = 1
sets TMDS clock ratio to 1/10 when set = 0
Return
True if write is successful, false otherwise.
HDMI Infoframes Helper Reference¶
Strictly speaking this is not a DRM helper library but generally useable by any driver interfacing with HDMI outputs like v4l or alsa drivers. But it nicely fits into the overall topic of mode setting helper libraries and hence is also included here.
-
struct
hdr_sink_metadata
¶ HDR sink metadata
Definition
struct hdr_sink_metadata {
__u32 metadata_type;
union {
struct hdr_static_metadata hdmi_type1;
};
};
Members
metadata_type
- Static_Metadata_Descriptor_ID.
{unnamed_union}
- anonymous
hdmi_type1
- HDR Metadata Infoframe.
Description
Metadata Information read from Sink’s EDID
-
union
hdmi_infoframe
¶ overall union of all abstract infoframe representations
Definition
union hdmi_infoframe {
struct hdmi_any_infoframe any;
struct hdmi_avi_infoframe avi;
struct hdmi_spd_infoframe spd;
union hdmi_vendor_any_infoframe vendor;
struct hdmi_audio_infoframe audio;
struct hdmi_drm_infoframe drm;
};
Members
any
- generic infoframe
avi
- avi infoframe
spd
- spd infoframe
vendor
- union of all vendor infoframes
audio
- audio infoframe
drm
- Dynamic Range and Mastering infoframe
Description
This is used by the generic pack function. This works since all infoframes have the same header which also indicates which type of infoframe should be packed.
-
void
hdmi_avi_infoframe_init
(struct hdmi_avi_infoframe *frame)¶ initialize an HDMI AVI infoframe
Parameters
struct hdmi_avi_infoframe *frame
- HDMI AVI infoframe
-
int
hdmi_avi_infoframe_check
(struct hdmi_avi_infoframe *frame)¶ check a HDMI AVI infoframe
Parameters
struct hdmi_avi_infoframe *frame
- HDMI AVI infoframe
Description
Validates that the infoframe is consistent and updates derived fields (eg. length) based on other fields.
Returns 0 on success or a negative error code on failure.
-
ssize_t
hdmi_avi_infoframe_pack_only
(const struct hdmi_avi_infoframe *frame, void *buffer, size_t size)¶ write HDMI AVI infoframe to binary buffer
Parameters
const struct hdmi_avi_infoframe *frame
- HDMI AVI infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. Also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
ssize_t
hdmi_avi_infoframe_pack
(struct hdmi_avi_infoframe *frame, void *buffer, size_t size)¶ check a HDMI AVI infoframe, and write it to binary buffer
Parameters
struct hdmi_avi_infoframe *frame
- HDMI AVI infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Validates that the infoframe is consistent and updates derived fields (eg. length) based on other fields, after which it packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. This function also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
int
hdmi_spd_infoframe_init
(struct hdmi_spd_infoframe *frame, const char *vendor, const char *product)¶ initialize an HDMI SPD infoframe
Parameters
struct hdmi_spd_infoframe *frame
- HDMI SPD infoframe
const char *vendor
- vendor string
const char *product
- product string
Description
Returns 0 on success or a negative error code on failure.
-
int
hdmi_spd_infoframe_check
(struct hdmi_spd_infoframe *frame)¶ check a HDMI SPD infoframe
Parameters
struct hdmi_spd_infoframe *frame
- HDMI SPD infoframe
Description
Validates that the infoframe is consistent and updates derived fields (eg. length) based on other fields.
Returns 0 on success or a negative error code on failure.
-
ssize_t
hdmi_spd_infoframe_pack_only
(const struct hdmi_spd_infoframe *frame, void *buffer, size_t size)¶ write HDMI SPD infoframe to binary buffer
Parameters
const struct hdmi_spd_infoframe *frame
- HDMI SPD infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. Also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
ssize_t
hdmi_spd_infoframe_pack
(struct hdmi_spd_infoframe *frame, void *buffer, size_t size)¶ check a HDMI SPD infoframe, and write it to binary buffer
Parameters
struct hdmi_spd_infoframe *frame
- HDMI SPD infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Validates that the infoframe is consistent and updates derived fields (eg. length) based on other fields, after which it packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. This function also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
int
hdmi_audio_infoframe_init
(struct hdmi_audio_infoframe *frame)¶ initialize an HDMI audio infoframe
Parameters
struct hdmi_audio_infoframe *frame
- HDMI audio infoframe
Description
Returns 0 on success or a negative error code on failure.
-
int
hdmi_audio_infoframe_check
(struct hdmi_audio_infoframe *frame)¶ check a HDMI audio infoframe
Parameters
struct hdmi_audio_infoframe *frame
- HDMI audio infoframe
Description
Validates that the infoframe is consistent and updates derived fields (eg. length) based on other fields.
Returns 0 on success or a negative error code on failure.
-
ssize_t
hdmi_audio_infoframe_pack_only
(const struct hdmi_audio_infoframe *frame, void *buffer, size_t size)¶ write HDMI audio infoframe to binary buffer
Parameters
const struct hdmi_audio_infoframe *frame
- HDMI audio infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. Also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
ssize_t
hdmi_audio_infoframe_pack
(struct hdmi_audio_infoframe *frame, void *buffer, size_t size)¶ check a HDMI Audio infoframe, and write it to binary buffer
Parameters
struct hdmi_audio_infoframe *frame
- HDMI Audio infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Validates that the infoframe is consistent and updates derived fields (eg. length) based on other fields, after which it packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. This function also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
int
hdmi_vendor_infoframe_init
(struct hdmi_vendor_infoframe *frame)¶ initialize an HDMI vendor infoframe
Parameters
struct hdmi_vendor_infoframe *frame
- HDMI vendor infoframe
Description
Returns 0 on success or a negative error code on failure.
-
int
hdmi_vendor_infoframe_check
(struct hdmi_vendor_infoframe *frame)¶ check a HDMI vendor infoframe
Parameters
struct hdmi_vendor_infoframe *frame
- HDMI infoframe
Description
Validates that the infoframe is consistent and updates derived fields (eg. length) based on other fields.
Returns 0 on success or a negative error code on failure.
-
ssize_t
hdmi_vendor_infoframe_pack_only
(const struct hdmi_vendor_infoframe *frame, void *buffer, size_t size)¶ write a HDMI vendor infoframe to binary buffer
Parameters
const struct hdmi_vendor_infoframe *frame
- HDMI infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. Also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
ssize_t
hdmi_vendor_infoframe_pack
(struct hdmi_vendor_infoframe *frame, void *buffer, size_t size)¶ check a HDMI Vendor infoframe, and write it to binary buffer
Parameters
struct hdmi_vendor_infoframe *frame
- HDMI Vendor infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Validates that the infoframe is consistent and updates derived fields (eg. length) based on other fields, after which it packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. This function also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
int
hdmi_drm_infoframe_init
(struct hdmi_drm_infoframe *frame)¶ initialize an HDMI Dynaminc Range and mastering infoframe
Parameters
struct hdmi_drm_infoframe *frame
- HDMI DRM infoframe
Description
Returns 0 on success or a negative error code on failure.
-
int
hdmi_drm_infoframe_check
(struct hdmi_drm_infoframe *frame)¶ check a HDMI DRM infoframe
Parameters
struct hdmi_drm_infoframe *frame
- HDMI DRM infoframe
Description
Validates that the infoframe is consistent. Returns 0 on success or a negative error code on failure.
-
ssize_t
hdmi_drm_infoframe_pack_only
(const struct hdmi_drm_infoframe *frame, void *buffer, size_t size)¶ write HDMI DRM infoframe to binary buffer
Parameters
const struct hdmi_drm_infoframe *frame
- HDMI DRM infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. Also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
ssize_t
hdmi_drm_infoframe_pack
(struct hdmi_drm_infoframe *frame, void *buffer, size_t size)¶ check a HDMI DRM infoframe, and write it to binary buffer
Parameters
struct hdmi_drm_infoframe *frame
- HDMI DRM infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Validates that the infoframe is consistent and updates derived fields (eg. length) based on other fields, after which it packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. This function also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
int
hdmi_infoframe_check
(union hdmi_infoframe *frame)¶ check a HDMI infoframe
Parameters
union hdmi_infoframe *frame
- HDMI infoframe
Description
Validates that the infoframe is consistent and updates derived fields (eg. length) based on other fields.
Returns 0 on success or a negative error code on failure.
-
ssize_t
hdmi_infoframe_pack_only
(const union hdmi_infoframe *frame, void *buffer, size_t size)¶ write a HDMI infoframe to binary buffer
Parameters
const union hdmi_infoframe *frame
- HDMI infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. Also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
ssize_t
hdmi_infoframe_pack
(union hdmi_infoframe *frame, void *buffer, size_t size)¶ check a HDMI infoframe, and write it to binary buffer
Parameters
union hdmi_infoframe *frame
- HDMI infoframe
void *buffer
- destination buffer
size_t size
- size of buffer
Description
Validates that the infoframe is consistent and updates derived fields (eg. length) based on other fields, after which it packs the information contained in the frame structure into a binary representation that can be written into the corresponding controller registers. This function also computes the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns the number of bytes packed into the binary buffer or a negative error code on failure.
-
void
hdmi_infoframe_log
(const char *level, struct device *dev, const union hdmi_infoframe *frame)¶ log info of HDMI infoframe
Parameters
const char *level
- logging level
struct device *dev
- device
const union hdmi_infoframe *frame
- HDMI infoframe
-
int
hdmi_drm_infoframe_unpack_only
(struct hdmi_drm_infoframe *frame, const void *buffer, size_t size)¶ unpack binary buffer of CTA-861-G DRM infoframe DataBytes to a HDMI DRM infoframe
Parameters
struct hdmi_drm_infoframe *frame
- HDMI DRM infoframe
const void *buffer
- source buffer
size_t size
- size of buffer
Description
Unpacks CTA-861-G DRM infoframe DataBytes contained in the binary buffer into a structured frame of the HDMI Dynamic Range and Mastering (DRM) infoframe.
Returns 0 on success or a negative error code on failure.
-
int
hdmi_infoframe_unpack
(union hdmi_infoframe *frame, const void *buffer, size_t size)¶ unpack binary buffer to a HDMI infoframe
Parameters
union hdmi_infoframe *frame
- HDMI infoframe
const void *buffer
- source buffer
size_t size
- size of buffer
Description
Unpacks the information contained in binary buffer buffer into a structured frame of a HDMI infoframe. Also verifies the checksum as required by section 5.3.5 of the HDMI 1.4 specification.
Returns 0 on success or a negative error code on failure.
Rectangle Utilities Reference¶
Utility functions to help manage rectangular areas for clipping, scaling, etc. calculations.
-
struct
drm_rect
¶ two dimensional rectangle
Definition
struct drm_rect {
int x1, y1, x2, y2;
};
Members
x1
- horizontal starting coordinate (inclusive)
y1
- vertical starting coordinate (inclusive)
x2
- horizontal ending coordinate (exclusive)
y2
- vertical ending coordinate (exclusive)
-
DRM_RECT_FMT
()¶ printf string for
struct drm_rect
Parameters
-
DRM_RECT_ARG
(r)¶ printf arguments for
struct drm_rect
Parameters
r
- rectangle struct
-
DRM_RECT_FP_FMT
()¶ printf string for
struct drm_rect
in 16.16 fixed point
Parameters
-
DRM_RECT_FP_ARG
(r)¶ printf arguments for
struct drm_rect
in 16.16 fixed point
Parameters
r
- rectangle struct
Description
This is useful for e.g. printing plane source rectangles, which are in 16.16 fixed point.
-
void
drm_rect_init
(struct drm_rect *r, int x, int y, int width, int height)¶ initialize the rectangle from x/y/w/h
Parameters
struct drm_rect *r
- rectangle
int x
- x coordinate
int y
- y coordinate
int width
- width
int height
- height
Parameters
struct drm_rect *r
- rectangle to be adjusted
int dw
- horizontal adjustment
int dh
- vertical adjustment
Description
Change the size of rectangle r by dw in the horizontal direction, and by dh in the vertical direction, while keeping the center of r stationary.
Positive dw and dh increase the size, negative values decrease it.
Parameters
struct drm_rect *r
- rectangle to be tranlated
int dx
- horizontal translation
int dy
- vertical translation
Description
Move rectangle r by dx in the horizontal direction, and by dy in the vertical direction.
-
void
drm_rect_translate_to
(struct drm_rect *r, int x, int y)¶ translate the rectangle to an absolute position
Parameters
struct drm_rect *r
- rectangle to be tranlated
int x
- horizontal position
int y
- vertical position
Description
Move rectangle r to x in the horizontal direction, and to y in the vertical direction.
Parameters
struct drm_rect *r
- rectangle to be downscaled
int horz
- horizontal downscale factor
int vert
- vertical downscale factor
Description
Divide the coordinates of rectangle r by horz and vert.
Parameters
const struct drm_rect *r
- rectangle whose width is returned
Return
The width of the rectangle.
Parameters
const struct drm_rect *r
- rectangle whose height is returned
Return
The height of the rectangle.
Parameters
const struct drm_rect *r
- rectangle whose visibility is returned
Return
true
if the rectangle is visible, false
otherwise.
-
bool
drm_rect_equals
(const struct drm_rect *r1, const struct drm_rect *r2)¶ determine if two rectangles are equal
Parameters
const struct drm_rect *r1
- first rectangle
const struct drm_rect *r2
- second rectangle
Return
true
if the rectangles are equal, false
otherwise.
Parameters
struct drm_rect *r1
- first rectangle
const struct drm_rect *r2
- second rectangle
Description
Calculate the intersection of rectangles r1 and r2. r1 will be overwritten with the intersection.
Return
true
if rectangle r1 is still visible after the operation,
false
otherwise.
-
bool
drm_rect_clip_scaled
(struct drm_rect *src, struct drm_rect *dst, const struct drm_rect *clip)¶ perform a scaled clip operation
Parameters
struct drm_rect *src
- source window rectangle
struct drm_rect *dst
- destination window rectangle
const struct drm_rect *clip
- clip rectangle
Description
Clip rectangle dst by rectangle clip. Clip rectangle src by the the corresponding amounts, retaining the vertical and horizontal scaling factors from src to dst.
true
if rectangle dst is still visible after being clipped,
false
otherwise.
Return
-
int
drm_rect_calc_hscale
(const struct drm_rect *src, const struct drm_rect *dst, int min_hscale, int max_hscale)¶ calculate the horizontal scaling factor
Parameters
const struct drm_rect *src
- source window rectangle
const struct drm_rect *dst
- destination window rectangle
int min_hscale
- minimum allowed horizontal scaling factor
int max_hscale
- maximum allowed horizontal scaling factor
Description
Calculate the horizontal scaling factor as (src width) / (dst width).
If the scale is below 1 << 16, round down. If the scale is above 1 << 16, round up. This will calculate the scale with the most pessimistic limit calculation.
Return
The horizontal scaling factor, or errno of out of limits.
-
int
drm_rect_calc_vscale
(const struct drm_rect *src, const struct drm_rect *dst, int min_vscale, int max_vscale)¶ calculate the vertical scaling factor
Parameters
const struct drm_rect *src
- source window rectangle
const struct drm_rect *dst
- destination window rectangle
int min_vscale
- minimum allowed vertical scaling factor
int max_vscale
- maximum allowed vertical scaling factor
Description
Calculate the vertical scaling factor as (src height) / (dst height).
If the scale is below 1 << 16, round down. If the scale is above 1 << 16, round up. This will calculate the scale with the most pessimistic limit calculation.
Return
The vertical scaling factor, or errno of out of limits.
-
void
drm_rect_debug_print
(const char *prefix, const struct drm_rect *r, bool fixed_point)¶ print the rectangle information
Parameters
const char *prefix
- prefix string
const struct drm_rect *r
- rectangle to print
bool fixed_point
- rectangle is in 16.16 fixed point format
-
void
drm_rect_rotate
(struct drm_rect *r, int width, int height, unsigned int rotation)¶ Rotate the rectangle
Parameters
struct drm_rect *r
- rectangle to be rotated
int width
- Width of the coordinate space
int height
- Height of the coordinate space
unsigned int rotation
- Transformation to be applied
Description
Apply rotation to the coordinates of rectangle r.
width and height combined with rotation define the location of the new origin.
width correcsponds to the horizontal and height to the vertical axis of the untransformed coordinate space.
-
void
drm_rect_rotate_inv
(struct drm_rect *r, int width, int height, unsigned int rotation)¶ Inverse rotate the rectangle
Parameters
struct drm_rect *r
- rectangle to be rotated
int width
- Width of the coordinate space
int height
- Height of the coordinate space
unsigned int rotation
- Transformation whose inverse is to be applied
Description
Apply the inverse of rotation to the coordinates of rectangle r.
width and height combined with rotation define the location of the new origin.
width correcsponds to the horizontal and height to the vertical axis of the original untransformed coordinate space, so that you never have to flip them when doing a rotatation and its inverse. That is, if you do
drm_rect_rotate(&r, width, height, rotation);
drm_rect_rotate_inv(&r, width, height, rotation);
you will always get back the original rectangle.
Flip-work Helper Reference¶
Util to queue up work to run from work-queue context after flip/vblank. Typically this can be used to defer unref of framebuffer’s, cursor bo’s, etc until after vblank. The APIs are all thread-safe. Moreover, drm_flip_work_queue_task and drm_flip_work_queue can be called in atomic context.
-
struct
drm_flip_task
¶ flip work task
Definition
struct drm_flip_task {
struct list_head node;
void *data;
};
Members
node
- list entry element
data
- data to pass to
drm_flip_work.func
-
struct
drm_flip_work
¶ flip work queue
Definition
struct drm_flip_work {
const char *name;
drm_flip_func_t func;
struct work_struct worker;
struct list_head queued;
struct list_head commited;
spinlock_t lock;
};
Members
name
- debug name
func
- callback fxn called for each committed item
worker
- worker which calls func
queued
- queued tasks
commited
- commited tasks
lock
- lock to access queued and commited lists
-
struct drm_flip_task *
drm_flip_work_allocate_task
(void *data, gfp_t flags)¶ allocate a flip-work task
Parameters
void *data
- data associated to the task
gfp_t flags
- allocator flags
Description
Allocate a drm_flip_task object and attach private data to it.
-
void
drm_flip_work_queue_task
(struct drm_flip_work *work, struct drm_flip_task *task)¶ queue a specific task
Parameters
struct drm_flip_work *work
- the flip-work
struct drm_flip_task *task
- the task to handle
Description
Queues task, that will later be run (passed back to drm_flip_func_t
func) on a work queue after drm_flip_work_commit()
is called.
-
void
drm_flip_work_queue
(struct drm_flip_work *work, void *val)¶ queue work
Parameters
struct drm_flip_work *work
- the flip-work
void *val
- the value to queue
Description
Queues work, that will later be run (passed back to drm_flip_func_t
func) on a work queue after drm_flip_work_commit()
is called.
-
void
drm_flip_work_commit
(struct drm_flip_work *work, struct workqueue_struct *wq)¶ commit queued work
Parameters
struct drm_flip_work *work
- the flip-work
struct workqueue_struct *wq
- the work-queue to run the queued work on
Description
Trigger work previously queued by drm_flip_work_queue()
to run
on a workqueue. The typical usage would be to queue work (via
drm_flip_work_queue()
) at any point (from vblank irq and/or
prior), and then from vblank irq commit the queued work.
-
void
drm_flip_work_init
(struct drm_flip_work *work, const char *name, drm_flip_func_t func)¶ initialize flip-work
Parameters
struct drm_flip_work *work
- the flip-work to initialize
const char *name
- debug name
drm_flip_func_t func
- the callback work function
Description
Initializes/allocates resources for the flip-work
-
void
drm_flip_work_cleanup
(struct drm_flip_work *work)¶ cleans up flip-work
Parameters
struct drm_flip_work *work
- the flip-work to cleanup
Description
Destroy resources allocated for the flip-work
Auxiliary Modeset Helpers¶
This helper library contains various one-off functions which don’t really fit anywhere else in the DRM modeset helper library.
-
void
drm_helper_move_panel_connectors_to_head
(struct drm_device *dev)¶ move panels to the front in the connector list
Parameters
struct drm_device *dev
- drm device to operate on
Description
Some userspace presumes that the first connected connector is the main display, where it’s supposed to display e.g. the login screen. For laptops, this should be the main panel. Use this function to sort all (eDP/LVDS/DSI) panels to the front of the connector list, instead of painstakingly trying to initialize them in the right order.
-
void
drm_helper_mode_fill_fb_struct
(struct drm_device *dev, struct drm_framebuffer *fb, const struct drm_mode_fb_cmd2 *mode_cmd)¶ fill out framebuffer metadata
Parameters
struct drm_device *dev
- DRM device
struct drm_framebuffer *fb
- drm_framebuffer object to fill out
const struct drm_mode_fb_cmd2 *mode_cmd
- metadata from the userspace fb creation request
Description
This helper can be used in a drivers fb_create callback to pre-fill the fb’s metadata fields.
-
int
drm_crtc_init
(struct drm_device *dev, struct drm_crtc *crtc, const struct drm_crtc_funcs *funcs)¶ Legacy CRTC initialization function
Parameters
struct drm_device *dev
- DRM device
struct drm_crtc *crtc
- CRTC object to init
const struct drm_crtc_funcs *funcs
- callbacks for the new CRTC
Description
Initialize a CRTC object with a default helper-provided primary plane and no cursor plane.
Note that we make some assumptions about hardware limitations that may not be true for all hardware:
- Primary plane cannot be repositioned.
- Primary plane cannot be scaled.
- Primary plane must cover the entire CRTC.
- Subpixel positioning is not supported.
- The primary plane must always be on if the CRTC is enabled.
This is purely a backwards compatibility helper for old drivers. Drivers
should instead implement their own primary plane. Atomic drivers must do so.
Drivers with the above hardware restriction can look into using struct
drm_simple_display_pipe
, which encapsulates the above limitations into a nice
interface.
Return
Zero on success, error code on failure.
-
int
drm_mode_config_helper_suspend
(struct drm_device *dev)¶ Modeset suspend helper
Parameters
struct drm_device *dev
- DRM device
Description
This helper function takes care of suspending the modeset side. It disables
output polling if initialized, suspends fbdev if used and finally calls
drm_atomic_helper_suspend()
.
If suspending fails, fbdev and polling is re-enabled.
See also:
drm_kms_helper_poll_disable()
and drm_fb_helper_set_suspend_unlocked()
.
Return
Zero on success, negative error code on error.
-
int
drm_mode_config_helper_resume
(struct drm_device *dev)¶ Modeset resume helper
Parameters
struct drm_device *dev
- DRM device
Description
This helper function takes care of resuming the modeset side. It calls
drm_atomic_helper_resume()
, resumes fbdev if used and enables output polling
if initiaized.
See also:
drm_fb_helper_set_suspend_unlocked()
and drm_kms_helper_poll_enable()
.
Return
Zero on success, negative error code on error.
OF/DT Helpers¶
A set of helper functions to aid DRM drivers in parsing standard DT properties.
-
uint32_t
drm_of_crtc_port_mask
(struct drm_device *dev, struct device_node *port)¶ find the mask of a registered CRTC by port OF node
Parameters
struct drm_device *dev
- DRM device
struct device_node *port
- port OF node
Description
Given a port OF node, return the possible mask of the corresponding CRTC within a device’s list of CRTCs. Returns zero if not found.
-
uint32_t
drm_of_find_possible_crtcs
(struct drm_device *dev, struct device_node *port)¶ find the possible CRTCs for an encoder port
Parameters
struct drm_device *dev
- DRM device
struct device_node *port
- encoder port to scan for endpoints
Description
Scan all endpoints attached to a port, locate their attached CRTCs, and generate the DRM mask of CRTCs which may be attached to this encoder.
See Documentation/devicetree/bindings/graph.txt for the bindings.
-
void
drm_of_component_match_add
(struct device *master, struct component_match **matchptr, int (*compare)(struct device *, void *), struct device_node *node)¶ Add a component helper OF node match rule
Parameters
struct device *master
- master device
struct component_match **matchptr
- component match pointer
int (*compare)(struct device *, void *)
- compare function used for matching component
struct device_node *node
- of_node
-
int
drm_of_component_probe
(struct device *dev, int (*compare_of)(struct device *, void *), const struct component_master_ops *m_ops)¶ Generic probe function for a component based master
Parameters
struct device *dev
- master device containing the OF node
int (*compare_of)(struct device *, void *)
- compare function used for matching components
const struct component_master_ops *m_ops
- component master ops to be used
Description
Parse the platform device OF node and bind all the components associated with the master. Interface ports are added before the encoders in order to satisfy their .bind requirements See Documentation/devicetree/bindings/graph.txt for the bindings.
Returns zero if successful, or one of the standard error codes if it fails.
-
int
drm_of_find_panel_or_bridge
(const struct device_node *np, int port, int endpoint, struct drm_panel **panel, struct drm_bridge **bridge)¶ return connected panel or bridge device
Parameters
const struct device_node *np
- device tree node containing encoder output ports
int port
- port in the device tree node
int endpoint
- endpoint in the device tree node
struct drm_panel **panel
- pointer to hold returned drm_panel
struct drm_bridge **bridge
- pointer to hold returned drm_bridge
Description
Given a DT node’s port and endpoint number, find the connected node and
return either the associated struct drm_panel
or drm_bridge device. Either
panel or bridge must not be NULL.
Returns zero if successful, or one of the standard error codes if it fails.
-
int
drm_of_lvds_get_dual_link_pixel_order
(const struct device_node *port1, const struct device_node *port2)¶ Get LVDS dual-link pixel order
Parameters
const struct device_node *port1
- First DT port node of the Dual-link LVDS source
const struct device_node *port2
- Second DT port node of the Dual-link LVDS source
Description
An LVDS dual-link connection is made of two links, with even pixels transitting on one link, and odd pixels on the other link. This function returns, for two ports of an LVDS dual-link source, which port shall transmit the even and odd pixels, based on the requirements of the connected sink.
The pixel order is determined from the dual-lvds-even-pixels and dual-lvds-odd-pixels properties in the sink’s DT port nodes. If those properties are not present, or if their usage is not valid, this function returns -EINVAL.
If either port is not connected, this function returns -EPIPE.
port1 and port2 are typically DT sibling nodes, but may have different parents when, for instance, two separate LVDS encoders carry the even and odd pixels.
Return
- DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS - port1 carries even pixels and port2 carries odd pixels
- DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS - port1 carries odd pixels and port2 carries even pixels
- -EINVAL - port1 and port2 are not connected to a dual-link LVDS sink, or the sink configuration is invalid
- -EPIPE - when port1 or port2 are not connected
Legacy Plane Helper Reference¶
This helper library has two parts. The first part has support to implement
primary plane support on top of the normal CRTC configuration interface.
Since the legacy drm_mode_config_funcs.set_config
interface ties the primary
plane together with the CRTC state this does not allow userspace to disable
the primary plane itself. The default primary plane only expose XRBG8888 and
ARGB8888 as valid pixel formats for the attached framebuffer.
Drivers are highly recommended to implement proper support for primary planes, and newly merged drivers must not rely upon these transitional helpers.
The second part also implements transitional helpers which allow drivers to gradually switch to the atomic helper infrastructure for plane updates. Once that switch is complete drivers shouldn’t use these any longer, instead using the proper legacy implementations for update and disable plane hooks provided by the atomic helpers.
Again drivers are strongly urged to switch to the new interfaces.
The plane helpers share the function table structures with other helpers,
specifically also the atomic helpers. See struct drm_plane_helper_funcs
for
the details.
Parameters
struct drm_plane *plane
- plane to destroy
Description
Provides a default plane destroy handler for primary planes. This handler is called during CRTC destruction. We disable the primary plane, remove it from the DRM plane list, and deallocate the plane structure.
Legacy CRTC/Modeset Helper Functions Reference¶
The CRTC modeset helper library provides a default set_config implementation
in drm_crtc_helper_set_config()
. Plus a few other convenience functions using
the same callbacks which drivers can use to e.g. restore the modeset
configuration on resume with drm_helper_resume_force_mode()
.
Note that this helper library doesn’t track the current power state of CRTCs
and encoders. It can call callbacks like drm_encoder_helper_funcs.dpms
even
though the hardware is already in the desired state. This deficiency has been
fixed in the atomic helpers.
The driver callbacks are mostly compatible with the atomic modeset helpers, except for the handling of the primary plane: Atomic helpers require that the primary plane is implemented as a real standalone plane and not directly tied to the CRTC state. For easier transition this library provides functions to implement the old semantics required by the CRTC helpers using the new plane and atomic helper callbacks.
Drivers are strongly urged to convert to the atomic helpers (by way of first converting to the plane helpers). New drivers must not use these functions but need to implement the atomic interface instead, potentially using the atomic helpers for that.
These legacy modeset helpers use the same function table structures as
all other modesetting helpers. See the documentation for struct
drm_crtc_helper_funcs
, struct drm_encoder_helper_funcs
and struct
drm_connector_helper_funcs
.
-
bool
drm_helper_encoder_in_use
(struct drm_encoder *encoder)¶ check if a given encoder is in use
Parameters
struct drm_encoder *encoder
- encoder to check
Description
Checks whether encoder is with the current mode setting output configuration in use by any connector. This doesn’t mean that it is actually enabled since the DPMS state is tracked separately.
Return
True if encoder is used, false otherwise.
Parameters
struct drm_crtc *crtc
- CRTC to check
Description
Checks whether crtc is with the current mode setting output configuration in use by any connector. This doesn’t mean that it is actually enabled since the DPMS state is tracked separately.
Return
True if crtc is used, false otherwise.
-
void
drm_helper_disable_unused_functions
(struct drm_device *dev)¶ disable unused objects
Parameters
struct drm_device *dev
- DRM device
Description
This function walks through the entire mode setting configuration of dev. It will remove any CRTC links of unused encoders and encoder links of disconnected connectors. Then it will disable all unused encoders and CRTCs either by calling their disable callback if available or by calling their dpms callback with DRM_MODE_DPMS_OFF.
This function is part of the legacy modeset helper library and will cause
major confusion with atomic drivers. This is because atomic helpers guarantee
to never call ->disable() hooks on a disabled function, or ->enable() hooks
on an enabled functions. drm_helper_disable_unused_functions()
on the other
hand throws such guarantees into the wind and calls disable hooks
unconditionally on unused functions.
NOTE
-
bool
drm_crtc_helper_set_mode
(struct drm_crtc *crtc, struct drm_display_mode *mode, int x, int y, struct drm_framebuffer *old_fb)¶ internal helper to set a mode
Parameters
struct drm_crtc *crtc
- CRTC to program
struct drm_display_mode *mode
- mode to use
int x
- horizontal offset into the surface
int y
- vertical offset into the surface
struct drm_framebuffer *old_fb
- old framebuffer, for cleanup
Description
Try to set mode on crtc. Give crtc and its associated connectors a chance
to fixup or reject the mode prior to trying to set it. This is an internal
helper that drivers could e.g. use to update properties that require the
entire output pipe to be disabled and re-enabled in a new configuration. For
example for changing whether audio is enabled on a hdmi link or for changing
panel fitter or dither attributes. It is also called by the
drm_crtc_helper_set_config()
helper function to drive the mode setting
sequence.
Return
True if the mode was set successfully, false otherwise.
-
int
drm_crtc_helper_set_config
(struct drm_mode_set *set, struct drm_modeset_acquire_ctx *ctx)¶ set a new config from userspace
Parameters
struct drm_mode_set *set
- mode set configuration
struct drm_modeset_acquire_ctx *ctx
- lock acquire context, not used here
Description
The drm_crtc_helper_set_config()
helper function implements the of
drm_crtc_funcs.set_config
callback for drivers using the legacy CRTC
helpers.
It first tries to locate the best encoder for each connector by calling the connector drm_connector_helper_funcs.best_encoder helper operation.
After locating the appropriate encoders, the helper function will call the mode_fixup encoder and CRTC helper operations to adjust the requested mode, or reject it completely in which case an error will be returned to the application. If the new configuration after mode adjustment is identical to the current configuration the helper function will return without performing any other operation.
If the adjusted mode is identical to the current mode but changes to the
frame buffer need to be applied, the drm_crtc_helper_set_config()
function
will call the CRTC drm_crtc_helper_funcs.mode_set_base
helper operation.
If the adjusted mode differs from the current mode, or if the
->mode_set_base() helper operation is not provided, the helper function
performs a full mode set sequence by calling the ->prepare(), ->mode_set()
and ->commit() CRTC and encoder helper operations, in that order.
Alternatively it can also use the dpms and disable helper operations. For
details see struct drm_crtc_helper_funcs
and struct
drm_encoder_helper_funcs
.
This function is deprecated. New drivers must implement atomic modeset support, fo