diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2024-03-13 11:14:55 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2024-03-13 11:14:55 -0700 |
| commit | 69afef4af453c913e31640f3b31103847b97fe2f (patch) | |
| tree | 5d81e6d8ec6abfed91f173050f6d7987d869ed65 /Documentation | |
| parent | 6cdebf62a159f31351946685b02941c968b96e49 (diff) | |
| parent | 8636f19c2d1f8199b27b4559d9caa115b3011f06 (diff) | |
| download | linux-69afef4af453c913e31640f3b31103847b97fe2f.tar.gz | |
Merge tag 'gpio-updates-for-v6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux
Pull gpio updates from Bartosz Golaszewski:
"The biggest feature is the locking overhaul. Up until now the
synchronization in the GPIO subsystem was broken. There was a single
spinlock "protecting" multiple data structures but doing it wrong (as
evidenced by several places where it would be released when a sleeping
function was called and then reacquired without checking the protected
state).
We tried to use an RW semaphore before but the main issue with GPIO is
that we have drivers implementing the interfaces in both sleeping and
non-sleeping ways as well as user-facing interfaces that can be called
both from process as well as atomic contexts. Both ends converge in
the same code paths that can use neither spinlocks nor mutexes. The
only reasonable way out is to use SRCU and go mostly lockless. To that
end: we add several SRCU structs in relevant places and use them to
assure consistency between API calls together with atomic reads and
writes of GPIO descriptor flags where it makes sense.
This code has spent several weeks in next and has received several
fixes in the first week or two after which it stabilized nicely. The
GPIO subsystem is now resilient to providers being suddenly unbound.
We managed to also remove the existing character device RW semaphore
and the obsolete global spinlock.
Other than the locking rework we have one new driver (for Chromebook
EC), much appreciated documentation improvements from Kent and the
regular driver improvements, DT-bindings updates and GPIOLIB core
tweaks.
Serialization rework:
- use SRCU to serialize access to the global GPIO device list, to
GPIO device structs themselves and to GPIO descriptors
- make the GPIO subsystem resilient to the GPIO providers being
unbound while the API calls are in progress
- don't dereference the SRCU-protected chip pointer if the
information we need can be obtained from the GPIO device structure
- move some of the information contained in struct gpio_chip to
struct gpio_device to further reduce the need to dereference the
former
- pass the GPIO device struct instead of the GPIO chip to sysfs
callback to, again, reduce the need for accessing the latter
- get GPIO descriptors from the GPIO device, not from the chip for
the same reason
- allow for mostly lockless operation of the GPIO driver API: assure
consistency with SRCU and atomic operations
- remove the global GPIO spinlock
- remove the character device RW semaphore
Core GPIOLIB:
- constify pointers in GPIO API where applicable
- unify the GPIO counting APIs for ACPI and OF
- provide a macro for iterating over all GPIOs, not only the ones
that are requested
- remove leftover typedefs
- pass the consumer device to GPIO core in
devm_fwnode_gpiod_get_index() for improved logging
- constify the GPIO bus type
- don't warn about removing GPIO chips with descriptors still held by
users as we can now handle this situation gracefully
- remove unused logging helpers
- unexport functions that are only used internally in the GPIO
subsystem
- set the device type (assign the relevant struct device_type) for
GPIO devices
New drivers:
- add the ChromeOS EC GPIO driver
Driver improvements:
- allow building gpio-vf610 with COMPILE_TEST as well as disabling it
in menuconfig (before it was always built for i.MX cofigs)
- count the number of EICs using the device properties instead of
hard-coding it in gpio-eic-sprd
- improve the device naming, extend the debugfs output and add
lockdep asserts to gpio-sim
DT bindings:
- document the 'label' property for gpio-pca9570
- convert aspeed,ast2400-gpio bindings to DT schema
- disallow unevaluated properties for gpio-mvebu
- document a new model in renesas,rcar-gpio
Documentation:
- improve the character device kerneldocs in user-space headers
- add proper documentation for the character device uAPI (both v1 and v2)
- move the sysfs and gpio-mockup docs into the "obsolete" section
- improve naming consistency for GPIO terms
- clarify the line values description for sysfs
- minor docs improvements
- improve the driver API contract for setting GPIO direction
- mark unsafe APIs as deprecated in kerneldocs and suggest
replacements
Other:
- remove an obsolete test from selftests"
* tag 'gpio-updates-for-v6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux: (79 commits)
gpio: sysfs: repair export returning -EPERM on 1st attempt
selftest: gpio: remove obsolete gpio-mockup test
gpiolib: Deduplicate cleanup for-loop in gpiochip_add_data_with_key()
dt-bindings: gpio: aspeed,ast2400-gpio: Convert to DT schema
gpio: acpi: Make acpi_gpio_count() take firmware node as a parameter
gpio: of: Make of_gpio_get_count() take firmware node as a parameter
gpiolib: Pass consumer device through to core in devm_fwnode_gpiod_get_index()
gpio: sim: use for_each_hwgpio()
gpio: provide for_each_hwgpio()
gpio: don't warn about removing GPIO chips with active users anymore
gpio: sim: delimit the fwnode name with a ":" when generating labels
gpio: sim: add lockdep asserts
gpio: Add ChromeOS EC GPIO driver
gpio: constify of_phandle_args in of_find_gpio_device_by_xlate()
gpio: fix memory leak in gpiod_request_commit()
gpio: constify opaque pointer "data" in gpio_device_find()
gpio: cdev: fix a NULL-pointer dereference with DEBUG enabled
gpio: uapi: clarify default_values being logical
gpio: sysfs: fix inverted pointer logic
gpio: don't let lockdep complain about inherently dangerous RCU usage
...
Diffstat (limited to 'Documentation')
37 files changed, 1916 insertions, 68 deletions
diff --git a/Documentation/ABI/obsolete/sysfs-gpio b/Documentation/ABI/obsolete/sysfs-gpio index b8b0fd341c1797..da1345d854b4ad 100644 --- a/Documentation/ABI/obsolete/sysfs-gpio +++ b/Documentation/ABI/obsolete/sysfs-gpio @@ -28,5 +28,5 @@ Description: /label ... (r/o) descriptive, not necessarily unique /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1) - This ABI is deprecated and will be removed after 2020. It is - replaced with the GPIO character device. + This ABI is obsoleted by Documentation/ABI/testing/gpio-cdev and will be + removed after 2020. diff --git a/Documentation/ABI/testing/gpio-cdev b/Documentation/ABI/testing/gpio-cdev index 66bdcd188b6c98..c9689b2a6fed21 100644 --- a/Documentation/ABI/testing/gpio-cdev +++ b/Documentation/ABI/testing/gpio-cdev @@ -6,8 +6,9 @@ Description: The character device files /dev/gpiochip* are the interface between GPIO chips and userspace. - The ioctl(2)-based ABI is defined and documented in - [include/uapi]<linux/gpio.h>. + The ioctl(2)-based ABI is defined in + [include/uapi]<linux/gpio.h> and documented in + Documentation/userspace-api/gpio/chardev.rst. The following file operations are supported: @@ -17,8 +18,8 @@ Description: ioctl(2) Initiate various actions. - See the inline documentation in [include/uapi]<linux/gpio.h> - for descriptions of all ioctls. + See Documentation/userspace-api/gpio/chardev.rst + for a description of all ioctls. close(2) Stops and free up the I/O contexts that was associated diff --git a/Documentation/admin-guide/gpio/gpio-mockup.rst b/Documentation/admin-guide/gpio/gpio-mockup.rst index 493071da1738c7..d6e7438a7550a9 100644 --- a/Documentation/admin-guide/gpio/gpio-mockup.rst +++ b/Documentation/admin-guide/gpio/gpio-mockup.rst @@ -3,6 +3,14 @@ GPIO Testing Driver =================== +.. note:: + + This module has been obsoleted by the more flexible gpio-sim.rst. + New developments should use that API and existing developments are + encouraged to migrate as soon as possible. + This module will continue to be maintained but no new features will be + added. + The GPIO Testing Driver (gpio-mockup) provides a way to create simulated GPIO chips for testing purposes. The lines exposed by these chips can be accessed using the standard GPIO character device interface as well as manipulated diff --git a/Documentation/admin-guide/gpio/index.rst b/Documentation/admin-guide/gpio/index.rst index f6861ca16ffe6b..460afd29617e0d 100644 --- a/Documentation/admin-guide/gpio/index.rst +++ b/Documentation/admin-guide/gpio/index.rst @@ -1,16 +1,16 @@ .. SPDX-License-Identifier: GPL-2.0 ==== -gpio +GPIO ==== .. toctree:: :maxdepth: 1 + Character Device Userspace API <../../userspace-api/gpio/chardev> gpio-aggregator - sysfs - gpio-mockup gpio-sim + Obsolete APIs <obsolete> .. only:: subproject and html diff --git a/Documentation/admin-guide/gpio/obsolete.rst b/Documentation/admin-guide/gpio/obsolete.rst new file mode 100644 index 00000000000000..5adbff02d61f43 --- /dev/null +++ b/Documentation/admin-guide/gpio/obsolete.rst @@ -0,0 +1,13 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================== +Obsolete GPIO APIs +================== + +.. toctree:: + :maxdepth: 1 + + Character Device Userspace API (v1) <../../userspace-api/gpio/chardev_v1> + Sysfs Interface <../../userspace-api/gpio/sysfs> + Mockup Testing Module <gpio-mockup> + diff --git a/Documentation/devicetree/bindings/gpio/aspeed,ast2400-gpio.yaml b/Documentation/devicetree/bindings/gpio/aspeed,ast2400-gpio.yaml new file mode 100644 index 00000000000000..cf11aa7ec8c7be --- /dev/null +++ b/Documentation/devicetree/bindings/gpio/aspeed,ast2400-gpio.yaml @@ -0,0 +1,148 @@ +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/gpio/aspeed,ast2400-gpio.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Aspeed GPIO controller + +maintainers: + - Andrew Jeffery <andrew@codeconstruct.com.au> + +properties: + compatible: + enum: + - aspeed,ast2400-gpio + - aspeed,ast2500-gpio + - aspeed,ast2600-gpio + + reg: + maxItems: 1 + + clocks: + maxItems: 1 + description: The clock to use for debounce timings + + gpio-controller: true + gpio-line-names: + minItems: 36 + maxItems: 232 + + gpio-ranges: true + + "#gpio-cells": + const: 2 + + interrupts: + maxItems: 1 + + interrupt-controller: true + + "#interrupt-cells": + const: 2 + + ngpios: + minimum: 36 + maximum: 232 + +required: + - compatible + - reg + - interrupts + - interrupt-controller + - "#interrupt-cells" + - gpio-controller + - "#gpio-cells" + +allOf: + - if: + properties: + compatible: + contains: + const: aspeed,ast2400-gpio + then: + properties: + gpio-line-names: + minItems: 220 + maxItems: 220 + ngpios: + const: 220 + - if: + properties: + compatible: + contains: + const: aspeed,ast2500-gpio + then: + properties: + gpio-line-names: + minItems: 232 + maxItems: 232 + ngpios: + const: 232 + - if: + properties: + compatible: + contains: + const: aspeed,ast2600-gpio + then: + properties: + gpio-line-names: + minItems: 36 + maxItems: 208 + ngpios: + enum: [ 36, 208 ] + required: + - ngpios + +additionalProperties: false + +examples: + - | + gpio@1e780000 { + compatible = "aspeed,ast2400-gpio"; + reg = <0x1e780000 0x1000>; + interrupts = <20>; + interrupt-controller; + #interrupt-cells = <2>; + gpio-controller; + #gpio-cells = <2>; + }; + - | + gpio: gpio@1e780000 { + compatible = "aspeed,ast2500-gpio"; + reg = <0x1e780000 0x200>; + interrupts = <20>; + interrupt-controller; + #interrupt-cells = <2>; + gpio-controller; + #gpio-cells = <2>; + gpio-ranges = <&pinctrl 0 0 232>; + }; + - | + #include <dt-bindings/clock/ast2600-clock.h> + #include <dt-bindings/interrupt-controller/arm-gic.h> + #include <dt-bindings/interrupt-controller/irq.h> + gpio0: gpio@1e780000 { + compatible = "aspeed,ast2600-gpio"; + reg = <0x1e780000 0x400>; + clocks = <&syscon ASPEED_CLK_APB2>; + interrupts = <GIC_SPI 40 IRQ_TYPE_LEVEL_HIGH>; + interrupt-controller; + #interrupt-cells = <2>; + #gpio-cells = <2>; + gpio-controller; + gpio-ranges = <&pinctrl 0 0 208>; + ngpios = <208>; + }; + gpio1: gpio@1e780800 { + compatible = "aspeed,ast2600-gpio"; + reg = <0x1e780800 0x800>; + clocks = <&syscon ASPEED_CLK_APB1>; + interrupts = <GIC_SPI 11 IRQ_TYPE_LEVEL_HIGH>; + interrupt-controller; + #interrupt-cells = <2>; + gpio-controller; + #gpio-cells = <2>; + gpio-ranges = <&pinctrl 0 208 36>; + ngpios = <36>; + }; diff --git a/Documentation/devicetree/bindings/gpio/gpio-aspeed.txt b/Documentation/devicetree/bindings/gpio/gpio-aspeed.txt deleted file mode 100644 index b2033fc3a71a6e..00000000000000 --- a/Documentation/devicetree/bindings/gpio/gpio-aspeed.txt +++ /dev/null @@ -1,39 +0,0 @@ -Aspeed GPIO controller Device Tree Bindings -------------------------------------------- - -Required properties: -- compatible : Either "aspeed,ast2400-gpio", "aspeed,ast2500-gpio", - or "aspeed,ast2600-gpio". - -- #gpio-cells : Should be two - - First cell is the GPIO line number - - Second cell is used to specify optional - parameters (unused) - -- reg : Address and length of the register set for the device -- gpio-controller : Marks the device node as a GPIO controller. -- interrupts : Interrupt specifier (see interrupt bindings for - details) -- interrupt-controller : Mark the GPIO controller as an interrupt-controller - -Optional properties: - -- clocks : A phandle to the clock to use for debounce timings -- ngpios : Number of GPIOs controlled by this controller. Should be set - when there are multiple GPIO controllers on a SoC (ast2600). - -The gpio and interrupt properties are further described in their respective -bindings documentation: - -- Documentation/devicetree/bindings/gpio/gpio.txt -- Documentation/devicetree/bindings/interrupt-controller/interrupts.txt - - Example: - gpio@1e780000 { - #gpio-cells = <2>; - compatible = "aspeed,ast2400-gpio"; - gpio-controller; - interrupts = <20>; - reg = <0x1e780000 0x1000>; - interrupt-controller; - }; diff --git a/Documentation/devicetree/bindings/gpio/gpio-mvebu.yaml b/Documentation/devicetree/bindings/gpio/gpio-mvebu.yaml index f1bd1e6b2e1f8d..33d4e4716516d5 100644 --- a/Documentation/devicetree/bindings/gpio/gpio-mvebu.yaml +++ b/Documentation/devicetree/bindings/gpio/gpio-mvebu.yaml @@ -115,7 +115,7 @@ allOf: required: - reg -unevaluatedProperties: true +unevaluatedProperties: false examples: - | diff --git a/Documentation/devicetree/bindings/gpio/gpio-pca9570.yaml b/Documentation/devicetree/bindings/gpio/gpio-pca9570.yaml index 452f8972a96590..6f73961001b75e 100644 --- a/Documentation/devicetree/bindings/gpio/gpio-pca9570.yaml +++ b/Documentation/devicetree/bindings/gpio/gpio-pca9570.yaml @@ -28,6 +28,9 @@ properties: minItems: 4 maxItems: 8 + label: + description: A descriptive name for this device. + required: - compatible - reg diff --git a/Documentation/devicetree/bindings/gpio/renesas,rcar-gpio.yaml b/Documentation/devicetree/bindings/gpio/renesas,rcar-gpio.yaml index aa424e2b95f87a..cc7a950a603099 100644 --- a/Documentation/devicetree/bindings/gpio/renesas,rcar-gpio.yaml +++ b/Documentation/devicetree/bindings/gpio/renesas,rcar-gpio.yaml @@ -53,6 +53,7 @@ properties: - renesas,gpio-r8a779a0 # R-Car V3U - renesas,gpio-r8a779f0 # R-Car S4-8 - renesas,gpio-r8a779g0 # R-Car V4H + - renesas,gpio-r8a779h0 # R-Car V4M - const: renesas,rcar-gen4-gpio # R-Car Gen4 reg: diff --git a/Documentation/driver-api/gpio/consumer.rst b/Documentation/driver-api/gpio/consumer.rst index 3e588b9d678cf9..ab56ab0dd7a693 100644 --- a/Documentation/driver-api/gpio/consumer.rst +++ b/Documentation/driver-api/gpio/consumer.rst @@ -222,9 +222,9 @@ Use the following calls to access GPIOs from an atomic context:: int gpiod_get_value(const struct gpio_desc *desc); void gpiod_set_value(struct gpio_desc *desc, int value); -The values are boolean, zero for low, nonzero for high. When reading the value -of an output pin, the value returned should be what's seen on the pin. That -won't always match the specified output value, because of issues including +The values are boolean, zero for inactive, nonzero for active. When reading the +value of an output pin, the value returned should be what's seen on the pin. +That won't always match the specified output value, because of issues including open-drain signaling and output latencies. The get/set calls do not return errors because "invalid GPIO" should have been @@ -277,11 +277,11 @@ switch their output to a high impedance value. The consumer should not need to care. (For details read about open drain in driver.rst.) With this, all the gpiod_set_(array)_value_xxx() functions interpret the -parameter "value" as "asserted" ("1") or "de-asserted" ("0"). The physical line +parameter "value" as "active" ("1") or "inactive" ("0"). The physical line level will be driven accordingly. As an example, if the active low property for a dedicated GPIO is set, and the -gpiod_set_(array)_value_xxx() passes "asserted" ("1"), the physical line level +gpiod_set_(array)_value_xxx() passes "active" ("1"), the physical line level will be driven low. To summarize:: diff --git a/Documentation/userspace-api/gpio/chardev.rst b/Documentation/userspace-api/gpio/chardev.rst new file mode 100644 index 00000000000000..c58dd9771ac9c0 --- /dev/null +++ b/Documentation/userspace-api/gpio/chardev.rst @@ -0,0 +1,116 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=================================== +GPIO Character Device Userspace API +=================================== + +This is latest version (v2) of the character device API, as defined in +``include/uapi/linux/gpio.h.`` + +First added in 5.10. + +.. note:: + Do NOT abuse userspace APIs to control hardware that has proper kernel + drivers. There may already be a driver for your use case, and an existing + kernel driver is sure to provide a superior solution to bitbashing + from userspace. + + Read Documentation/driver-api/gpio/drivers-on-gpio.rst to avoid reinventing + kernel wheels in userspace. + + Similarly, for multi-function lines there may be other subsystems, such as + Documentation/spi/index.rst, Documentation/i2c/index.rst, + Documentation/driver-api/pwm.rst, Documentation/w1/index.rst etc, that + provide suitable drivers and APIs for your hardware. + +Basic examples using the character device API can be found in ``tools/gpio/*``. + +The API is based around two major objects, the :ref:`gpio-v2-chip` and the +:ref:`gpio-v2-line-request`. + +.. _gpio-v2-chip: + +Chip +==== + +The Chip represents a single GPIO chip and is exposed to userspace using device +files of the form ``/dev/gpiochipX``. + +Each chip supports a number of GPIO lines, +:c:type:`chip.lines<gpiochip_info>`. Lines on the chip are identified by an +``offset`` in the range from 0 to ``chip.lines - 1``, i.e. `[0,chip.lines)`. + +Lines are requested from the chip using gpio-v2-get-line-ioctl.rst +and the resulting line request is used to access the GPIO chip's lines or +monitor the lines for edge events. + +Within this documentation, the file descriptor returned by calling `open()` +on the GPIO device file is referred to as ``chip_fd``. + +Operations +---------- + +The following operations may be performed on the chip: + +.. toctree:: + :titlesonly: + + Get Line <gpio-v2-get-line-ioctl> + Get Chip Info <gpio-get-chipinfo-ioctl> + Get Line Info <gpio-v2-get-lineinfo-ioctl> + Watch Line Info <gpio-v2-get-lineinfo-watch-ioctl> + Unwatch Line Info <gpio-get-lineinfo-unwatch-ioctl> + Read Line Info Changed Events <gpio-v2-lineinfo-changed-read> + +.. _gpio-v2-line-request: + +Line Request +============ + +Line requests are created by gpio-v2-get-line-ioctl.rst and provide +access to a set of requested lines. The line request is exposed to userspace +via the anonymous file descriptor returned in +:c:type:`request.fd<gpio_v2_line_request>` by gpio-v2-get-line-ioctl.rst. + +Within this documentation, the line request file descriptor is referred to +as ``req_fd``. + +Operations +---------- + +The following operations may be performed on the line request: + +.. toctree:: + :titlesonly: + + Get Line Values <gpio-v2-line-get-values-ioctl> + Set Line Values <gpio-v2-line-set-values-ioctl> + Read Line Edge Events <gpio-v2-line-event-read> + Reconfigure Lines <gpio-v2-line-set-config-ioctl> + +Types +===== + +This section contains the structs and enums that are referenced by the API v2, +as defined in ``include/uapi/linux/gpio.h``. + +.. kernel-doc:: include/uapi/linux/gpio.h + :identifiers: + gpio_v2_line_attr_id + gpio_v2_line_attribute + gpio_v2_line_changed_type + gpio_v2_line_config + gpio_v2_line_config_attribute + gpio_v2_line_event + gpio_v2_line_event_id + gpio_v2_line_flag + gpio_v2_line_info + gpio_v2_line_info_changed + gpio_v2_line_request + gpio_v2_line_values + gpiochip_info + +.. toctree:: + :hidden: + + error-codes diff --git a/Documentation/userspace-api/gpio/chardev_v1.rst b/Documentation/userspace-api/gpio/chardev_v1.rst new file mode 100644 index 00000000000000..67124b1d048794 --- /dev/null +++ b/Documentation/userspace-api/gpio/chardev_v1.rst @@ -0,0 +1,131 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================================== +GPIO Character Device Userspace API (v1) +======================================== + +.. warning:: + This API is obsoleted by chardev.rst (v2). + + New developments should use the v2 API, and existing developments are + encouraged to migrate as soon as possible, as this API will be removed + in the future. The v2 API is a functional superset of the v1 API so any + v1 call can be directly translated to a v2 equivalent. + + This interface will continue to be maintained for the migration period, + but new features will only be added to the new API. + +First added in 4.8. + +The API is based around three major objects, the :ref:`gpio-v1-chip`, the +:ref:`gpio-v1-line-handle`, and the :ref:`gpio-v1-line-event`. + +Where "line event" is used in this document it refers to the request that can +monitor a line for edge events, not the edge events themselves. + +.. _gpio-v1-chip: + +Chip +==== + +The Chip represents a single GPIO chip and is exposed to userspace using device +files of the form ``/dev/gpiochipX``. + +Each chip supports a number of GPIO lines, +:c:type:`chip.lines<gpiochip_info>`. Lines on the chip are identified by an +``offset`` in the range from 0 to ``chip.lines - 1``, i.e. `[0,chip.lines)`. + +Lines are requested from the chip using either gpio-get-linehandle-ioctl.rst +and the resulting line handle is used to access the GPIO chip's lines, or +gpio-get-lineevent-ioctl.rst and the resulting line event is used to monitor +a GPIO line for edge events. + +Within this documentation, the file descriptor returned by calling `open()` +on the GPIO device file is referred to as ``chip_fd``. + +Operations +---------- + +The following operations may be performed on the chip: + +.. toctree:: + :titlesonly: + + Get Line Handle <gpio-get-linehandle-ioctl> + Get Line Event <gpio-get-lineevent-ioctl> + Get Chip Info <gpio-get-chipinfo-ioctl> + Get Line Info <gpio-get-lineinfo-ioctl> + Watch Line Info <gpio-get-lineinfo-watch-ioctl> + Unwatch Line Info <gpio-get-lineinfo-unwatch-ioctl> + Read Line Info Changed Events <gpio-lineinfo-changed-read> + +.. _gpio-v1-line-handle: + +Line Handle +=========== + +Line handles are created by gpio-get-linehandle-ioctl.rst and provide +access to a set of requested lines. The line handle is exposed to userspace +via the anonymous file descriptor returned in +:c:type:`request.fd<gpiohandle_request>` by gpio-get-linehandle-ioctl.rst. + +Within this documentation, the line handle file descriptor is referred to +as ``handle_fd``. + +Operations +---------- + +The following operations may be performed on the line handle: + +.. toctree:: + :titlesonly: + + Get Line Values <gpio-handle-get-line-values-ioctl> + Set Line Values <gpio-handle-set-line-values-ioctl> + Reconfigure Lines <gpio-handle-set-config-ioctl> + +.. _gpio-v1-line-event: + +Line Event +========== + +Line events are created by gpio-get-lineevent-ioctl.rst and provide +access to a requested line. The line event is exposed to userspace +via the anonymous file descriptor returned in +:c:type:`request.fd<gpioevent_request>` by gpio-get-lineevent-ioctl.rst. + +Within this documentation, the line event file descriptor is referred to +as ``event_fd``. + +Operations +---------- + +The following operations may be performed on the line event: + +.. toctree:: + :titlesonly: + + Get Line Value <gpio-handle-get-line-values-ioctl> + Read Line Edge Events <gpio-lineevent-data-read> + +Types +===== + +This section contains the structs that are referenced by the ABI v1. + +The :c:type:`struct gpiochip_info<gpiochip_info>` is common to ABI v1 and v2. + +.. kernel-doc:: include/uapi/linux/gpio.h + :identifiers: + gpioevent_data + gpioevent_request + gpiohandle_config + gpiohandle_data + gpiohandle_request + gpioline_info + gpioline_info_changed + +.. toctree:: + :hidden: + + error-codes diff --git a/Documentation/userspace-api/gpio/error-codes.rst b/Documentation/userspace-api/gpio/error-codes.rst new file mode 100644 index 00000000000000..6bf2948990cdcc --- /dev/null +++ b/Documentation/userspace-api/gpio/error-codes.rst @@ -0,0 +1,79 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _gpio_errors: + +******************* +GPIO Error Codes +******************* + +.. _gpio-errors: + +.. tabularcolumns:: |p{2.5cm}|p{15.0cm}| + +.. flat-table:: Common GPIO error codes + :header-rows: 0 + :stub-columns: 0 + :widths: 1 16 + + - - ``EAGAIN`` (aka ``EWOULDBLOCK``) + + - The device was opened in non-blocking mode and a read can't + be performed as there is no data available. + + - - ``EBADF`` + + - The file descriptor is not valid. + + - - ``EBUSY`` + + - The ioctl can't be handled because the device is busy. Typically + returned when an ioctl attempts something that would require the + usage of a resource that was already allocated. The ioctl must not + be retried without performing another action to fix the problem + first. + + - - ``EFAULT`` + + - There was a failure while copying data from/to userspace, probably + caused by an invalid pointer reference. + + - - ``EINVAL`` + + - One or more of the ioctl parameters are invalid or out of the + allowed range. This is a widely used error code. + + - - ``ENODEV`` + + - Device not found or was removed. + + - - ``ENOMEM`` + + - There's not enough memory to handle the desired operation. + + - - ``EPERM`` + + - Permission denied. Typically returned in response to an attempt + to perform an action incompatible with the current line + configuration. + + - - ``EIO`` + + - I/O error. Typically returned when there are problems communicating + with a hardware device or requesting features that hardware does not + support. This could indicate broken or flaky hardware. + It's a 'Something is wrong, I give up!' type of error. + + - - ``ENXIO`` + + - Typically returned when a feature requiring interrupt support was + requested, but the line does not support interrupts. + +.. note:: + + #. This list is not exhaustive; ioctls may return other error codes. + Since errors may have side effects such as a driver reset, + applications should abort on unexpected errors, or otherwise + assume that the device is in a bad state. + + #. Request-specific error codes are listed in the individual + requests descriptions. diff --git a/Documentation/userspace-api/gpio/gpio-get-chipinfo-ioctl.rst b/Documentation/userspace-api/gpio/gpio-get-chipinfo-ioctl.rst new file mode 100644 index 00000000000000..05f07fdefe2f64 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-get-chipinfo-ioctl.rst @@ -0,0 +1,41 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_GET_CHIPINFO_IOCTL: + +*********************** +GPIO_GET_CHIPINFO_IOCTL +*********************** + +Name +==== + +GPIO_GET_CHIPINFO_IOCTL - Get the publicly available information for a chip. + +Synopsis +======== + +.. c:macro:: GPIO_GET_CHIPINFO_IOCTL + +``int ioctl(int chip_fd, GPIO_GET_CHIPINFO_IOCTL, struct gpiochip_info *info)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``info`` + The :c:type:`chip_info<gpiochip_info>` to be populated. + +Description +=========== + +Gets the publicly available information for a particular GPIO chip. + +Return Value +============ + +On success 0 and ``info`` is populated with the chip info. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-get-lineevent-ioctl.rst b/Documentation/userspace-api/gpio/gpio-get-lineevent-ioctl.rst new file mode 100644 index 00000000000000..09a9254f38cffd --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-get-lineevent-ioctl.rst @@ -0,0 +1,84 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_GET_LINEEVENT_IOCTL: + +************************ +GPIO_GET_LINEEVENT_IOCTL +************************ + +.. warning:: + This ioctl is part of chardev_v1.rst and is obsoleted by + gpio-v2-get-line-ioctl.rst. + +Name +==== + +GPIO_GET_LINEEVENT_IOCTL - Request a line with edge detection from the kernel. + +Synopsis +======== + +.. c:macro:: GPIO_GET_LINEEVENT_IOCTL + +``int ioctl(int chip_fd, GPIO_GET_LINEEVENT_IOCTL, struct gpioevent_request *request)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``request`` + The :c:type:`event_request<gpioevent_request>` specifying the line + to request and its configuration. + +Description +=========== + +Request a line with edge detection from the kernel. + +On success, the requesting process is granted exclusive access to the line +value and may receive events when edges are detected on the line, as +described in gpio-lineevent-data-read.rst. + +The state of a line is guaranteed to remain as requested until the returned +file descriptor is closed. Once the file descriptor is closed, the state of +the line becomes uncontrolled from the userspace perspective, and may revert +to its default state. + +Requesting a line already in use is an error (**EBUSY**). + +Requesting edge detection on a line that does not support interrupts is an +error (**ENXIO**). + +As with the :ref:`line handle<gpio-get-linehandle-config-support>`, the +bias configuration is best effort. + +Closing the ``chip_fd`` has no effect on existing line events. + +Configuration Rules +------------------- + +The following configuration rules apply: + +The line event is requested as an input, so no flags specific to output lines, +``GPIOHANDLE_REQUEST_OUTPUT``, ``GPIOHANDLE_REQUEST_OPEN_DRAIN``, or +``GPIOHANDLE_REQUEST_OPEN_SOURCE``, may be set. + +Only one bias flag, ``GPIOHANDLE_REQUEST_BIAS_xxx``, may be set. +If no bias flags are set then the bias configuration is not changed. + +The edge flags, ``GPIOEVENT_REQUEST_RISING_EDGE`` and +``GPIOEVENT_REQUEST_FALLING_EDGE``, may be combined to detect both rising +and falling edges. + +Requesting an invalid configuration is an error (**EINVAL**). + +Return Value +============ + +On success 0 and the :c:type:`request.fd<gpioevent_request>` contains the file +descriptor for the request. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-get-linehandle-ioctl.rst b/Documentation/userspace-api/gpio/gpio-get-linehandle-ioctl.rst new file mode 100644 index 00000000000000..9112a9d31174f7 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-get-linehandle-ioctl.rst @@ -0,0 +1,125 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_GET_LINEHANDLE_IOCTL: + +************************* +GPIO_GET_LINEHANDLE_IOCTL +************************* + +.. warning:: + This ioctl is part of chardev_v1.rst and is obsoleted by + gpio-v2-get-line-ioctl.rst. + +Name +==== + +GPIO_GET_LINEHANDLE_IOCTL - Request a line or lines from the kernel. + +Synopsis +======== + +.. c:macro:: GPIO_GET_LINEHANDLE_IOCTL + +``int ioctl(int chip_fd, GPIO_GET_LINEHANDLE_IOCTL, struct gpiohandle_request *request)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``request`` + The :c:type:`handle_request<gpiohandle_request>` specifying the lines to + request and their configuration. + +Description +=========== + +Request a line or lines from the kernel. + +While multiple lines may be requested, the same configuration applies to all +lines in the request. + +On success, the requesting process is granted exclusive access to the line +value and write access to the line configuration. + +The state of a line, including the value of output lines, is guaranteed to +remain as requested until the returned file descriptor is closed. Once the +file descriptor is closed, the state of the line becomes uncontrolled from +the userspace perspective, and may revert to its default state. + +Requesting a line already in use is an error (**EBUSY**). + +Closing the ``chip_fd`` has no effect on existing line handles. + +.. _gpio-get-linehandle-config-rules: + +Configuration Rules +------------------- + +The following configuration rules apply: + +The direction flags, ``GPIOHANDLE_REQUEST_INPUT`` and +``GPIOHANDLE_REQUEST_OUTPUT``, cannot be combined. If neither are set then the +only other flag that may be set is ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` and the +line is requested "as-is" to allow reading of the line value without altering +the electrical configuration. + +The drive flags, ``GPIOHANDLE_REQUEST_OPEN_xxx``, require the +``GPIOHANDLE_REQUEST_OUTPUT`` to be set. +Only one drive flag may be set. +If none are set then the line is assumed push-pull. + +Only one bias flag, ``GPIOHANDLE_REQUEST_BIAS_xxx``, may be set, and +it requires a direction flag to also be set. +If no bias flags are set then the bias configuration is not changed. + +Requesting an invalid configuration is an error (**EINVAL**). + + +.. _gpio-get-linehandle-config-support: + +Configuration Support +--------------------- + +Where the requested configuration is not directly supported by the underlying +hardware and driver, the kernel applies one of these approaches: + + - reject the request + - emulate the feature in software + - treat the feature as best effort + +The approach applied depends on whether the feature can reasonably be emulated +in software, and the impact on the hardware and userspace if the feature is not +supported. +The approach applied for each feature is as follows: + +============== =========== +Feature Approach +============== =========== +Bias best effort +Direction reject +Drive emulate +============== =========== + +Bias is treated as best effort to allow userspace to apply the same +configuration for platforms that support internal bias as those that require +external bias. +Worst case the line floats rather than being biased as expected. + +Drive is emulated by switching the line to an input when the line should not +be driven. + +In all cases, the configuration reported by gpio-get-lineinfo-ioctl.rst +is the requested configuration, not the resulting hardware configuration. +Userspace cannot determine if a feature is supported in hardware, is +emulated, or is best effort. + +Return Value +============ + +On success 0 and the :c:type:`request.fd<gpiohandle_request>` contains the +file descriptor for the request. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-get-lineinfo-ioctl.rst b/Documentation/userspace-api/gpio/gpio-get-lineinfo-ioctl.rst new file mode 100644 index 00000000000000..c895b8910b252a --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-get-lineinfo-ioctl.rst @@ -0,0 +1,54 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_GET_LINEINFO_IOCTL: + +*********************** +GPIO_GET_LINEINFO_IOCTL +*********************** + +.. warning:: + This ioctl is part of chardev_v1.rst and is obsoleted by + gpio-v2-get-lineinfo-ioctl.rst. + +Name +==== + +GPIO_GET_LINEINFO_IOCTL - Get the publicly available information for a line. + +Synopsis +======== + +.. c:macro:: GPIO_GET_LINEINFO_IOCTL + +``int ioctl(int chip_fd, GPIO_GET_LINEINFO_IOCTL, struct gpioline_info *info)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``info`` + The :c:type:`line_info<gpioline_info>` to be populated, with the + ``offset`` field set to indicate the line to be collected. + +Description +=========== + +Get the publicly available information for a line. + +This information is available independent of whether the line is in use. + +.. note:: + The line info does not include the line value. + + The line must be requested using gpio-get-linehandle-ioctl.rst or + gpio-get-lineevent-ioctl.rst to access its value. + +Return Value +============ + +On success 0 and ``info`` is populated with the chip info. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-get-lineinfo-unwatch-ioctl.rst b/Documentation/userspace-api/gpio/gpio-get-lineinfo-unwatch-ioctl.rst new file mode 100644 index 00000000000000..a82d0161daf871 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-get-lineinfo-unwatch-ioctl.rst @@ -0,0 +1,49 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_GET_LINEINFO_UNWATCH_IOCTL: + +******************************* +GPIO_GET_LINEINFO_UNWATCH_IOCTL +******************************* + +Name +==== + +GPIO_GET_LINEINFO_UNWATCH_IOCTL - Disable watching a line for changes to its +requested state and configuration information. + +Synopsis +======== + +.. c:macro:: GPIO_GET_LINEINFO_UNWATCH_IOCTL + +``int ioctl(int chip_fd, GPIO_GET_LINEINFO_UNWATCH_IOCTL, u32 *offset)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``offset`` + The offset of the line to no longer watch. + +Description +=========== + +Remove the line from the list of lines being watched on this ``chip_fd``. + +This is the reverse of gpio-v2-get-lineinfo-watch-ioctl.rst (v2) and +gpio-get-lineinfo-watch-ioctl.rst (v1). + +Unwatching a line that is not watched is an error (**EBUSY**). + +First added in 5.7. + +Return Value +============ + +On success 0. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-get-lineinfo-watch-ioctl.rst b/Documentation/userspace-api/gpio/gpio-get-lineinfo-watch-ioctl.rst new file mode 100644 index 00000000000000..f5c92b69a4961b --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-get-lineinfo-watch-ioctl.rst @@ -0,0 +1,74 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_GET_LINEINFO_WATCH_IOCTL: + +***************************** +GPIO_GET_LINEINFO_WATCH_IOCTL +***************************** + +.. warning:: + This ioctl is part of chardev_v1.rst and is obsoleted by + gpio-v2-get-lineinfo-watch-ioctl.rst. + +Name +==== + +GPIO_GET_LINEINFO_WATCH_IOCTL - Enable watching a line for changes to its +request state and configuration information. + +Synopsis +======== + +.. c:macro:: GPIO_GET_LINEINFO_WATCH_IOCTL + +``int ioctl(int chip_fd, GPIO_GET_LINEINFO_WATCH_IOCTL, struct gpioline_info *info)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``info`` + The :c:type:`line_info<gpioline_info>` struct to be populated, with + the ``offset`` set to indicate the line to watch + +Description +=========== + +Enable watching a line for changes to its request state and configuration +information. Changes to line info include a line being requested, released +or reconfigured. + +.. note:: + Watching line info is not generally required, and would typically only be + used by a system monitoring component. + + The line info does NOT include the line value. + + The line must be requested using gpio-get-linehandle-ioctl.rst or + gpio-get-lineevent-ioctl.rst to access its value, and the line event can + monitor a line for events using gpio-lineevent-data-read.rst. + +By default all lines are unwatched when the GPIO chip is opened. + +Multiple lines may be watched simultaneously by adding a watch for each. + +Once a watch is set, any changes to line info will generate events which can be +read from the ``chip_fd`` as described in +gpio-lineinfo-changed-read.rst. + +Adding a watch to a line that is already watched is an error (**EBUSY**). + +Watches are specific to the ``chip_fd`` and are independent of watches +on the same GPIO chip opened with a separate call to `open()`. + +First added in 5.7. + +Return Value +============ + +On success 0 and ``info`` is populated with the current line info. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-handle-get-line-values-ioctl.rst b/Documentation/userspace-api/gpio/gpio-handle-get-line-values-ioctl.rst new file mode 100644 index 00000000000000..25263b8f058885 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-handle-get-line-values-ioctl.rst @@ -0,0 +1,56 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIOHANDLE_GET_LINE_VALUES_IOCTL: + +******************************** +GPIOHANDLE_GET_LINE_VALUES_IOCTL +******************************** +.. warning:: + This ioctl is part of chardev_v1.rst and is obsoleted by + gpio-v2-line-get-values-ioctl.rst. + +Name +==== + +GPIOHANDLE_GET_LINE_VALUES_IOCTL - Get the values of all requested lines. + +Synopsis +======== + +.. c:macro:: GPIOHANDLE_GET_LINE_VALUES_IOCTL + +``int ioctl(int handle_fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, struct gpiohandle_data *values)`` + +Arguments +========= + +``handle_fd`` + The file descriptor of the GPIO character device, as returned in the + :c:type:`request.fd<gpiohandle_request>` by gpio-get-linehandle-ioctl.rst. + +``values`` + The :c:type:`line_values<gpiohandle_data>` to be populated. + +Description +=========== + +Get the values of all requested lines. + +The values of both input and output lines may be read. + +For output lines, the value returned is driver and configuration dependent and +may be either the output buffer (the last requested value set) or the input +buffer (the actual level of the line), and depending on the hardware and +configuration these may differ. + +This ioctl can also be used to read the line value for line events, +substituting the ``event_fd`` for the ``handle_fd``. As there is only +one line requested in that case, only the one value is returned in ``values``. + +Return Value +============ + +On success 0 and ``values`` populated with the values read. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-handle-set-config-ioctl.rst b/Documentation/userspace-api/gpio/gpio-handle-set-config-ioctl.rst new file mode 100644 index 00000000000000..d002a84681acf9 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-handle-set-config-ioctl.rst @@ -0,0 +1,63 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIOHANDLE_SET_CONFIG_IOCTL: + +*************************** +GPIOHANDLE_SET_CONFIG_IOCTL +*************************** + +.. warning:: + This ioctl is part of chardev_v1.rst and is obsoleted by + gpio-v2-line-set-config-ioctl.rst. + +Name +==== + +GPIOHANDLE_SET_CONFIG_IOCTL - Update the configuration of previously requested lines. + +Synopsis +======== + +.. c:macro:: GPIOHANDLE_SET_CONFIG_IOCTL + +``int ioctl(int handle_fd, GPIOHANDLE_SET_CONFIG_IOCTL, struct gpiohandle_config *config)`` + +Arguments +========= + +``handle_fd`` + The file descriptor of the GPIO character device, as returned in the + :c:type:`request.fd<gpiohandle_request>` by gpio-get-linehandle-ioctl.rst. + +``config`` + The new :c:type:`configuration<gpiohandle_config>` to apply to the + requested lines. + +Description +=========== + +Update the configuration of previously requested lines, without releasing the +line or introducing potential glitches. + +The configuration applies to all requested lines. + +The same :ref:`gpio-get-linehandle-config-rules` and +:ref:`gpio-get-linehandle-config-support` that apply when requesting the +lines also apply when updating the line configuration. + +The motivating use case for this command is changing direction of +bi-directional lines between input and output, but it may be used more +generally to move lines seamlessly from one configuration state to another. + +To only change the value of output lines, use +gpio-handle-set-line-values-ioctl.rst. + +First added in 5.5. + +Return Value +============ + +On success 0. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-handle-set-line-values-ioctl.rst b/Documentation/userspace-api/gpio/gpio-handle-set-line-values-ioctl.rst new file mode 100644 index 00000000000000..0aa05e623a6c80 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-handle-set-line-values-ioctl.rst @@ -0,0 +1,48 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_HANDLE_SET_LINE_VALUES_IOCTL: + +********************************* +GPIO_HANDLE_SET_LINE_VALUES_IOCTL +********************************* +.. warning:: + This ioctl is part of chardev_v1.rst and is obsoleted by + gpio-v2-line-set-values-ioctl.rst. + +Name +==== + +GPIO_HANDLE_SET_LINE_VALUES_IOCTL - Set the values of all requested output lines. + +Synopsis +======== + +.. c:macro:: GPIO_HANDLE_SET_LINE_VALUES_IOCTL + +``int ioctl(int handle_fd, GPIO_HANDLE_SET_LINE_VALUES_IOCTL, struct gpiohandle_data *values)`` + +Arguments +========= + +``handle_fd`` + The file descriptor of the GPIO character device, as returned in the + :c:type:`request.fd<gpiohandle_request>` by gpio-get-linehandle-ioctl.rst. + +``values`` + The :c:type:`line_values<gpiohandle_data>` to set. + +Description +=========== + +Set the values of all requested output lines. + +Only the values of output lines may be set. +Attempting to set the value of input lines is an error (**EPERM**). + +Return Value +============ + +On success 0. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-lineevent-data-read.rst b/Documentation/userspace-api/gpio/gpio-lineevent-data-read.rst new file mode 100644 index 00000000000000..68b8d4f9f604c4 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-lineevent-data-read.rst @@ -0,0 +1,84 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_LINEEVENT_DATA_READ: + +************************ +GPIO_LINEEVENT_DATA_READ +************************ + +.. warning:: + This ioctl is part of chardev_v1.rst and is obsoleted by + gpio-v2-line-event-read.rst. + +Name +==== + +GPIO_LINEEVENT_DATA_READ - Read edge detection events from a line event. + +Synopsis +======== + +``int read(int event_fd, void *buf, size_t count)`` + +Arguments +========= + +``event_fd`` + The file descriptor of the GPIO character device, as returned in the + :c:type:`request.fd<gpioevent_request>` by gpio-get-lineevent-ioctl.rst. + +``buf`` + The buffer to contain the :c:type:`events<gpioevent_data>`. + +``count`` + The number of bytes available in ``buf``, which must be at + least the size of a :c:type:`gpioevent_data`. + +Description +=========== + +Read edge detection events for a line from a line event. + +Edge detection must be enabled for the input line using either +``GPIOEVENT_REQUEST_RISING_EDGE`` or ``GPIOEVENT_REQUEST_FALLING_EDGE``, or +both. Edge events are then generated whenever edge interrupts are detected on +the input line. + +The kernel captures and timestamps edge events as close as possible to their +occurrence and stores them in a buffer from where they can be read by +userspace at its convenience using `read()`. + +The source of the clock for :c:type:`event.timestamp<gpioevent_data>` is +``CLOCK_MONOTONIC``, except for kernels earlier than Linux 5.7 when it was +``CLOCK_REALTIME``. There is no indication in the :c:type:`gpioevent_data` +as to which clock source is used, it must be determined from either the kernel +version or sanity checks on the timestamp itself. + +Events read from the buffer are always in the same order that they were +detected by the kernel. + +The size of the kernel event buffer is fixed at 16 events. + +The buffer may overflow if bursts of events occur quicker than they are read +by userspace. If an overflow occurs then the most recent event is discarded. +Overflow cannot be detected from userspace. + +To minimize the number of calls required to copy events from the kernel to +userspace, `read()` supports copying multiple events. The number of events +copied is the lower of the number available in the kernel buffer and the +number that will fit in the userspace buffer (``buf``). + +The `read()` will block if no event is available and the ``event_fd`` has not +been set **O_NONBLOCK**. + +The presence of an event can be tested for by checking that the ``event_fd`` is +readable using `poll()` or an equivalent. + +Return Value +============ + +On success the number of bytes read, which will be a multiple of the size of +a :c:type:`gpio_lineevent_data` event. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-lineinfo-changed-read.rst b/Documentation/userspace-api/gpio/gpio-lineinfo-changed-read.rst new file mode 100644 index 00000000000000..c4f5e1787a9df5 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-lineinfo-changed-read.rst @@ -0,0 +1,87 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_LINEINFO_CHANGED_READ: + +************************** +GPIO_LINEINFO_CHANGED_READ +************************** + +.. warning:: + This ioctl is part of chardev_v1.rst and is obsoleted by + gpio-v2-lineinfo-changed-read.rst. + +Name +==== + +GPIO_LINEINFO_CHANGED_READ - Read line info change events for watched lines +from the chip. + +Synopsis +======== + +``int read(int chip_fd, void *buf, size_t count)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``buf`` + The buffer to contain the :c:type:`events<gpioline_info_changed>`. + +``count`` + The number of bytes available in ``buf``, which must be at least the size + of a :c:type:`gpioline_info_changed` event. + +Description +=========== + +Read line info change events for watched lines from the chip. + +.. note:: + Monitoring line info changes is not generally required, and would typically + only be performed by a system monitoring component. + + These events relate to changes in a line's request state or configuration, + not its value. Use gpio-lineevent-data-read.rst to receive events when a + line changes value. + +A line must be watched using gpio-get-lineinfo-watch-ioctl.rst to generate +info changed events. Subsequently, a request, release, or reconfiguration +of the line will generate an info changed event. + +The kernel timestamps events when they occur and stores them in a buffer +from where they can be read by userspace at its convenience using `read()`. + +The size of the kernel event buffer is fixed at 32 events per ``chip_fd``. + +The buffer may overflow if bursts of events occur quicker than they are read +by userspace. If an overflow occurs then the most recent event is discarded. +Overflow cannot be detected from userspace. + +Events read from the buffer are always in the same order that they were +detected by the kernel, including when multiple lines are being monitored by +the one ``chip_fd``. + +To minimize the number of calls required to copy events from the kernel to +userspace, `read()` supports copying multiple events. The number of events +copied is the lower of the number available in the kernel buffer and the +number that will fit in the userspace buffer (``buf``). + +A `read()` will block if no event is available and the ``chip_fd`` has not +been set **O_NONBLOCK**. + +The presence of an event can be tested for by checking that the ``chip_fd`` is +readable using `poll()` or an equivalent. + +First added in 5.7. + +Return Value +============ + +On success the number of bytes read, which will be a multiple of the size of +a :c:type:`gpioline_info_changed` event. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-v2-get-line-ioctl.rst b/Documentation/userspace-api/gpio/gpio-v2-get-line-ioctl.rst new file mode 100644 index 00000000000000..56b975801b6af0 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-v2-get-line-ioctl.rst @@ -0,0 +1,152 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_V2_GET_LINE_IOCTL: + +********************** +GPIO_V2_GET_LINE_IOCTL +********************** + +Name +==== + +GPIO_V2_GET_LINE_IOCTL - Request a line or lines from the kernel. + +Synopsis +======== + +.. c:macro:: GPIO_V2_GET_LINE_IOCTL + +``int ioctl(int chip_fd, GPIO_V2_GET_LINE_IOCTL, struct gpio_v2_line_request *request)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``request`` + The :c:type:`line_request<gpio_v2_line_request>` specifying the lines + to request and their configuration. + +Description +=========== + +On success, the requesting process is granted exclusive access to the line +value, write access to the line configuration, and may receive events when +edges are detected on the line, all of which are described in more detail in +:ref:`gpio-v2-line-request`. + +A number of lines may be requested in the one line request, and request +operations are performed on the requested lines by the kernel as atomically +as possible. e.g. gpio-v2-line-get-values-ioctl.rst will read all the +requested lines at once. + +The state of a line, including the value of output lines, is guaranteed to +remain as requested until the returned file descriptor is closed. Once the +file descriptor is closed, the state of the line becomes uncontrolled from +the userspace perspective, and may revert to its default state. + +Requesting a line already in use is an error (**EBUSY**). + +Closing the ``chip_fd`` has no effect on existing line requests. + +.. _gpio-v2-get-line-config-rules: + +Configuration Rules +------------------- + +For any given requested line, the following configuration rules apply: + +The direction flags, ``GPIO_V2_LINE_FLAG_INPUT`` and +``GPIO_V2_LINE_FLAG_OUTPUT``, cannot be combined. If neither are set then +the only other flag that may be set is ``GPIO_V2_LINE_FLAG_ACTIVE_LOW`` +and the line is requested "as-is" to allow reading of the line value +without altering the electrical configuration. + +The drive flags, ``GPIO_V2_LINE_FLAG_OPEN_xxx``, require the +``GPIO_V2_LINE_FLAG_OUTPUT`` to be set. +Only one drive flag may be set. +If none are set then the line is assumed push-pull. + +Only one bias flag, ``GPIO_V2_LINE_FLAG_BIAS_xxx``, may be set, and it +requires a direction flag to also be set. +If no bias flags are set then the bias configuration is not changed. + +The edge flags, ``GPIO_V2_LINE_FLAG_EDGE_xxx``, require +``GPIO_V2_LINE_FLAG_INPUT`` to be set and may be combined to detect both rising +and falling edges. Requesting edge detection from a line that does not support +it is an error (**ENXIO**). + +Only one event clock flag, ``GPIO_V2_LINE_FLAG_EVENT_CLOCK_xxx``, may be set. +If none are set then the event clock defaults to ``CLOCK_MONOTONIC``. +The ``GPIO_V2_LINE_FLAG_EVENT_CLOCK_HTE`` flag requires supporting hardware +and a kernel with ``CONFIG_HTE`` set. Requesting HTE from a device that +doesn't support it is an error (**EOPNOTSUP**). + +The :c:type:`debounce_period_us<gpio_v2_line_attribute>` attribute may only +be applied to lines with ``GPIO_V2_LINE_FLAG_INPUT`` set. When set, debounce +applies to both the values returned by gpio-v2-line-get-values-ioctl.rst and +the edges returned by gpio-v2-line-event-read.rst. If not +supported directly by hardware, debouncing is emulated in software by the +kernel. Requesting debounce on a line that supports neither debounce in +hardware nor interrupts, as required for software emulation, is an error +(**ENXIO**). + +Requesting an invalid configuration is an error (**EINVAL**). + +.. _gpio-v2-get-line-config-support: + +Configuration Support +--------------------- + +Where the requested configuration is not directly supported by the underlying +hardware and driver, the kernel applies one of these approaches: + + - reject the request + - emulate the feature in software + - treat the feature as best effort + +The approach applied depends on whether the feature can reasonably be emulated +in software, and the impact on the hardware and userspace if the feature is not +supported. +The approach applied for each feature is as follows: + +============== =========== +Feature Approach +============== =========== +Bias best effort +Debounce emulate +Direction reject +Drive emulate +Edge Detection reject +============== =========== + +Bias is treated as best effort to allow userspace to apply the same +configuration for platforms that support internal bias as those that require +external bias. +Worst case the line floats rather than being biased as expected. + +Debounce is emulated by applying a filter to hardware interrupts on the line. +An edge event is generated after an edge is detected and the line remains +stable for the debounce period. +The event timestamp corresponds to the end of the debounce period. + +Drive is emulated by switching the line to an input when the line should not +be actively driven. + +Edge detection requires interrupt support, and is rejected if that is not +supported. Emulation by polling can still be performed from userspace. + +In all cases, the configuration reported by gpio-v2-get-lineinfo-ioctl.rst +is the requested configuration, not the resulting hardware configuration. +Userspace cannot determine if a feature is supported in hardware, is +emulated, or is best effort. + +Return Value +============ + +On success 0 and the :c:type:`request.fd<gpio_v2_line_request>` contains the +file descriptor for the request. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-v2-get-lineinfo-ioctl.rst b/Documentation/userspace-api/gpio/gpio-v2-get-lineinfo-ioctl.rst new file mode 100644 index 00000000000000..bc4d8df887d40f --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-v2-get-lineinfo-ioctl.rst @@ -0,0 +1,50 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_V2_GET_LINEINFO_IOCTL: + +************************** +GPIO_V2_GET_LINEINFO_IOCTL +************************** + +Name +==== + +GPIO_V2_GET_LINEINFO_IOCTL - Get the publicly available information for a line. + +Synopsis +======== + +.. c:macro:: GPIO_V2_GET_LINEINFO_IOCTL + +``int ioctl(int chip_fd, GPIO_V2_GET_LINEINFO_IOCTL, struct gpio_v2_line_info *info)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``info`` + The :c:type:`line_info<gpio_v2_line_info>` to be populated, with the + ``offset`` field set to indicate the line to be collected. + +Description +=========== + +Get the publicly available information for a line. + +This information is available independent of whether the line is in use. + +.. note:: + The line info does not include the line value. + + The line must be requested using gpio-v2-get-line-ioctl.rst to access its + value. + +Return Value +============ + +On success 0 and ``info`` is populated with the chip info. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-v2-get-lineinfo-watch-ioctl.rst b/Documentation/userspace-api/gpio/gpio-v2-get-lineinfo-watch-ioctl.rst new file mode 100644 index 00000000000000..938ff85a93226f --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-v2-get-lineinfo-watch-ioctl.rst @@ -0,0 +1,67 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_V2_GET_LINEINFO_WATCH_IOCTL: + +******************************** +GPIO_V2_GET_LINEINFO_WATCH_IOCTL +******************************** + +Name +==== + +GPIO_V2_GET_LINEINFO_WATCH_IOCTL - Enable watching a line for changes to its +request state and configuration information. + +Synopsis +======== + +.. c:macro:: GPIO_V2_GET_LINEINFO_WATCH_IOCTL + +``int ioctl(int chip_fd, GPIO_V2_GET_LINEINFO_WATCH_IOCTL, struct gpio_v2_line_info *info)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``info`` + The :c:type:`line_info<gpio_v2_line_info>` struct to be populated, with + the ``offset`` set to indicate the line to watch + +Description +=========== + +Enable watching a line for changes to its request state and configuration +information. Changes to line info include a line being requested, released +or reconfigured. + +.. note:: + Watching line info is not generally required, and would typically only be + used by a system monitoring component. + + The line info does NOT include the line value. + The line must be requested using gpio-v2-get-line-ioctl.rst to access + its value, and the line request can monitor a line for events using + gpio-v2-line-event-read.rst. + +By default all lines are unwatched when the GPIO chip is opened. + +Multiple lines may be watched simultaneously by adding a watch for each. + +Once a watch is set, any changes to line info will generate events which can be +read from the ``chip_fd`` as described in +gpio-v2-lineinfo-changed-read.rst. + +Adding a watch to a line that is already watched is an error (**EBUSY**). + +Watches are specific to the ``chip_fd`` and are independent of watches +on the same GPIO chip opened with a separate call to `open()`. + +Return Value +============ + +On success 0 and ``info`` is populated with the current line info. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-v2-line-event-read.rst b/Documentation/userspace-api/gpio/gpio-v2-line-event-read.rst new file mode 100644 index 00000000000000..6513c23fb7cada --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-v2-line-event-read.rst @@ -0,0 +1,83 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_V2_LINE_EVENT_READ: + +*********************** +GPIO_V2_LINE_EVENT_READ +*********************** + +Name +==== + +GPIO_V2_LINE_EVENT_READ - Read edge detection events for lines from a request. + +Synopsis +======== + +``int read(int req_fd, void *buf, size_t count)`` + +Arguments +========= + +``req_fd`` + The file descriptor of the GPIO character device, as returned in the + :c:type:`request.fd<gpio_v2_line_request>` by gpio-v2-get-line-ioctl.rst. + +``buf`` + The buffer to contain the :c:type:`events<gpio_v2_line_event>`. + +``count`` + The number of bytes available in ``buf``, which must be at + least the size of a :c:type:`gpio_v2_line_event`. + +Description +=========== + +Read edge detection events for lines from a request. + +Edge detection must be enabled for the input line using either +``GPIO_V2_LINE_FLAG_EDGE_RISING`` or ``GPIO_V2_LINE_FLAG_EDGE_FALLING``, or +both. Edge events are then generated whenever edge interrupts are detected on +the input line. + +The kernel captures and timestamps edge events as close as possible to their +occurrence and stores them in a buffer from where they can be read by +userspace at its convenience using `read()`. + +Events read from the buffer are always in the same order that they were +detected by the kernel, including when multiple lines are being monitored by +the one request. + +The size of the kernel event buffer is fixed at the time of line request +creation, and can be influenced by the +:c:type:`request.event_buffer_size<gpio_v2_line_request>`. +The default size is 16 times the number of lines requested. + +The buffer may overflow if bursts of events occur quicker than they are read +by userspace. If an overflow occurs then the oldest buffered event is +discarded. Overflow can be detected from userspace by monitoring the event +sequence numbers. + +To minimize the number of calls required to copy events from the kernel to +userspace, `read()` supports copying multiple events. The number of events +copied is the lower of the number available in the kernel buffer and the +number that will fit in the userspace buffer (``buf``). + +Changing the edge detection flags using gpio-v2-line-set-config-ioctl.rst +does not remove or modify the events already contained in the kernel event +buffer. + +The `read()` will block if no event is available and the ``req_fd`` has not +been set **O_NONBLOCK**. + +The presence of an event can be tested for by checking that the ``req_fd`` is +readable using `poll()` or an equivalent. + +Return Value +============ + +On success the number of bytes read, which will be a multiple of the size of a +:c:type:`gpio_v2_line_event` event. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-v2-line-get-values-ioctl.rst b/Documentation/userspace-api/gpio/gpio-v2-line-get-values-ioctl.rst new file mode 100644 index 00000000000000..e4e74a1926d823 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-v2-line-get-values-ioctl.rst @@ -0,0 +1,51 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_V2_LINE_GET_VALUES_IOCTL: + +***************************** +GPIO_V2_LINE_GET_VALUES_IOCTL +***************************** + +Name +==== + +GPIO_V2_LINE_GET_VALUES_IOCTL - Get the values of requested lines. + +Synopsis +======== + +.. c:macro:: GPIO_V2_LINE_GET_VALUES_IOCTL + +``int ioctl(int req_fd, GPIO_V2_LINE_GET_VALUES_IOCTL, struct gpio_v2_line_values *values)`` + +Arguments +========= + +``req_fd`` + The file descriptor of the GPIO character device, as returned in the + :c:type:`request.fd<gpio_v2_line_request>` by gpio-v2-get-line-ioctl.rst. + +``values`` + The :c:type:`line_values<gpio_v2_line_values>` to get with the ``mask`` set + to indicate the subset of requested lines to get. + +Description +=========== + +Get the values of requested lines. + +The values of both input and output lines may be read. + +For output lines, the value returned is driver and configuration dependent and +may be either the output buffer (the last requested value set) or the input +buffer (the actual level of the line), and depending on the hardware and +configuration these may differ. + +Return Value +============ + +On success 0 and the corresponding :c:type:`values.bits<gpio_v2_line_values>` +contain the value read. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-v2-line-set-config-ioctl.rst b/Documentation/userspace-api/gpio/gpio-v2-line-set-config-ioctl.rst new file mode 100644 index 00000000000000..9b942a8a53ca9a --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-v2-line-set-config-ioctl.rst @@ -0,0 +1,58 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_V2_LINE_SET_CONFIG_IOCTL: + +***************************** +GPIO_V2_LINE_SET_CONFIG_IOCTL +***************************** + +Name +==== + +GPIO_V2_LINE_SET_CONFIG_IOCTL - Update the configuration of previously requested lines. + +Synopsis +======== + +.. c:macro:: GPIO_V2_LINE_SET_CONFIG_IOCTL + +``int ioctl(int req_fd, GPIO_V2_LINE_SET_CONFIG_IOCTL, struct gpio_v2_line_config *config)`` + +Arguments +========= + +``req_fd`` + The file descriptor of the GPIO character device, as returned in the + :c:type:`request.fd<gpio_v2_line_request>` by gpio-v2-get-line-ioctl.rst. + +``config`` + The new :c:type:`configuration<gpio_v2_line_config>` to apply to the + requested lines. + +Description +=========== + +Update the configuration of previously requested lines, without releasing the +line or introducing potential glitches. + +The new configuration must specify the configuration of all requested lines. + +The same :ref:`gpio-v2-get-line-config-rules` and +:ref:`gpio-v2-get-line-config-support` that apply when requesting the lines +also apply when updating the line configuration. + +The motivating use case for this command is changing direction of +bi-directional lines between input and output, but it may also be used to +dynamically control edge detection, or more generally move lines seamlessly +from one configuration state to another. + +To only change the value of output lines, use +gpio-v2-line-set-values-ioctl.rst. + +Return Value +============ + +On success 0. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-v2-line-set-values-ioctl.rst b/Documentation/userspace-api/gpio/gpio-v2-line-set-values-ioctl.rst new file mode 100644 index 00000000000000..6d2d1886950b6b --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-v2-line-set-values-ioctl.rst @@ -0,0 +1,47 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_V2_LINE_SET_VALUES_IOCTL: + +***************************** +GPIO_V2_LINE_SET_VALUES_IOCTL +***************************** + +Name +==== + +GPIO_V2_LINE_SET_VALUES_IOCTL - Set the values of requested output lines. + +Synopsis +======== + +.. c:macro:: GPIO_V2_LINE_SET_VALUES_IOCTL + +``int ioctl(int req_fd, GPIO_V2_LINE_SET_VALUES_IOCTL, struct gpio_v2_line_values *values)`` + +Arguments +========= + +``req_fd`` + The file descriptor of the GPIO character device, as returned in the + :c:type:`request.fd<gpio_v2_line_request>` by gpio-v2-get-line-ioctl.rst. + +``values`` + The :c:type:`line_values<gpio_v2_line_values>` to set with the ``mask`` set + to indicate the subset of requested lines to set and ``bits`` set to + indicate the new value. + +Description +=========== + +Set the values of requested output lines. + +Only the values of output lines may be set. +Attempting to set the value of an input line is an error (**EPERM**). + +Return Value +============ + +On success 0. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/gpio-v2-lineinfo-changed-read.rst b/Documentation/userspace-api/gpio/gpio-v2-lineinfo-changed-read.rst new file mode 100644 index 00000000000000..24ad325e725353 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-v2-lineinfo-changed-read.rst @@ -0,0 +1,81 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_V2_LINEINFO_CHANGED_READ: + +***************************** +GPIO_V2_LINEINFO_CHANGED_READ +***************************** + +Name +==== + +GPIO_V2_LINEINFO_CHANGED_READ - Read line info changed events for watched +lines from the chip. + +Synopsis +======== + +``int read(int chip_fd, void *buf, size_t count)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``buf`` + The buffer to contain the :c:type:`events<gpio_v2_line_info_changed>`. + +``count`` + The number of bytes available in ``buf``, which must be at least the size + of a :c:type:`gpio_v2_line_info_changed` event. + +Description +=========== + +Read line info changed events for watched lines from the chip. + +.. note:: + Monitoring line info changes is not generally required, and would typically + only be performed by a system monitoring component. + + These events relate to changes in a line's request state or configuration, + not its value. Use gpio-v2-line-event-read.rst to receive events when a + line changes value. + +A line must be watched using gpio-v2-get-lineinfo-watch-ioctl.rst to generate +info changed events. Subsequently, a request, release, or reconfiguration +of the line will generate an info changed event. + +The kernel timestamps events when they occur and stores them in a buffer +from where they can be read by userspace at its convenience using `read()`. + +The size of the kernel event buffer is fixed at 32 events per ``chip_fd``. + +The buffer may overflow if bursts of events occur quicker than they are read +by userspace. If an overflow occurs then the most recent event is discarded. +Overflow cannot be detected from userspace. + +Events read from the buffer are always in the same order that they were +detected by the kernel, including when multiple lines are being monitored by +the one ``chip_fd``. + +To minimize the number of calls required to copy events from the kernel to +userspace, `read()` supports copying multiple events. The number of events +copied is the lower of the number available in the kernel buffer and the +number that will fit in the userspace buffer (``buf``). + +A `read()` will block if no event is available and the ``chip_fd`` has not +been set **O_NONBLOCK**. + +The presence of an event can be tested for by checking that the ``chip_fd`` is +readable using `poll()` or an equivalent. + +Return Value +============ + +On success the number of bytes read, which will be a multiple of the size +of a :c:type:`gpio_v2_line_info_changed` event. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. diff --git a/Documentation/userspace-api/gpio/index.rst b/Documentation/userspace-api/gpio/index.rst new file mode 100644 index 00000000000000..f258de4ef370f7 --- /dev/null +++ b/Documentation/userspace-api/gpio/index.rst @@ -0,0 +1,18 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==== +GPIO +==== + +.. toctree:: + :maxdepth: 1 + + Character Device Userspace API <chardev> + Obsolete Userspace APIs <obsolete> + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/userspace-api/gpio/obsolete.rst b/Documentation/userspace-api/gpio/obsolete.rst new file mode 100644 index 00000000000000..c42538b44ec8cc --- /dev/null +++ b/Documentation/userspace-api/gpio/obsolete.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================ +Obsolete GPIO Userspace APIs +============================ + +.. toctree:: + :maxdepth: 1 + + Character Device Userspace API (v1) <chardev_v1> + Sysfs Interface <sysfs> diff --git a/Documentation/admin-guide/gpio/sysfs.rst b/Documentation/userspace-api/gpio/sysfs.rst index 35171d15f78d46..116921048b18e9 100644 --- a/Documentation/admin-guide/gpio/sysfs.rst +++ b/Documentation/userspace-api/gpio/sysfs.rst @@ -2,18 +2,18 @@ GPIO Sysfs Interface for Userspace ================================== .. warning:: + This API is obsoleted by the chardev.rst and the ABI documentation has + been moved to Documentation/ABI/obsolete/sysfs-gpio. - THIS ABI IS DEPRECATED, THE ABI DOCUMENTATION HAS BEEN MOVED TO - Documentation/ABI/obsolete/sysfs-gpio AND NEW USERSPACE CONSUMERS - ARE SUPPOSED TO USE THE CHARACTER DEVICE ABI. THIS OLD SYSFS ABI WILL - NOT BE DEVELOPED (NO NEW FEATURES), IT WILL JUST BE MAINTAINED. + New developments should use the chardev.rst, and existing developments are + encouraged to migrate as soon as possible, as this API will be removed + in the future. -Refer to the examples in tools/gpio/* for an introduction to the new -character device ABI. Also see the userspace header in -include/uapi/linux/gpio.h + This interface will continue to be maintained for the migration period, + but new features will only be added to the new API. -The deprecated sysfs ABI ------------------------- +The obsolete sysfs ABI +---------------------- Platforms which use the "gpiolib" implementors framework may choose to configure a sysfs user interface to GPIOs. This is different from the debugfs interface, since it provides control over GPIO direction and @@ -33,9 +33,12 @@ userspace GPIO can be used to determine system configuration data that standard kernels won't know about. And for some tasks, simple userspace GPIO drivers could be all that the system really needs. -DO NOT ABUSE SYSFS TO CONTROL HARDWARE THAT HAS PROPER KERNEL DRIVERS. -PLEASE READ THE DOCUMENT AT Documentation/driver-api/gpio/drivers-on-gpio.rst -TO AVOID REINVENTING KERNEL WHEELS IN USERSPACE. I MEAN IT. REALLY. +.. note:: + Do NOT abuse sysfs to control hardware that has proper kernel drivers. + Please read Documentation/driver-api/gpio/drivers-on-gpio.rst + to avoid reinventing kernel wheels in userspace. + + I MEAN IT. REALLY. Paths in Sysfs -------------- @@ -84,9 +87,9 @@ and have the following read/write attributes: allow userspace to reconfigure this GPIO's direction. "value" ... - reads as either 0 (low) or 1 (high). If the GPIO + reads as either 0 (inactive) or 1 (active). If the GPIO is configured as an output, this value may be written; - any nonzero value is treated as high. + any nonzero value is treated as active. If the pin can be configured as interrupt-generating interrupt and if it has been configured to generate interrupts (see the diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst index 67d663cf2ff263..afecfe3cc4a86b 100644 --- a/Documentation/userspace-api/index.rst +++ b/Documentation/userspace-api/index.rst @@ -42,6 +42,7 @@ Devices and I/O accelerators/ocxl dma-buf-alloc-exchange + gpio/index iommu iommufd media/index |