1sphinx.addnodesdocument)}( rawsourcechildren]( translations LanguagesNode)}(hhh](h pending_xref)}(hhh]docutils.nodesTextChinese (Simplified)}(hhparenthuba attributes}(ids]classes]names]dupnames]backrefs] refdomainstdreftypedoc reftarget%/translations/zh_CN/hid/hid-transportmodnameN classnameN refexplicitutagnamehhh ubh)}(hhh]hChinese (Traditional)}(hhhh2ubah}(h]h ]h"]h$]h&] refdomainh)reftypeh+ reftarget%/translations/zh_TW/hid/hid-transportmodnameN classnameN refexplicituh1hhh ubh)}(hhh]hItalian}(hhhhFubah}(h]h ]h"]h$]h&] refdomainh)reftypeh+ reftarget%/translations/it_IT/hid/hid-transportmodnameN classnameN refexplicituh1hhh ubh)}(hhh]hJapanese}(hhhhZubah}(h]h ]h"]h$]h&] refdomainh)reftypeh+ reftarget%/translations/ja_JP/hid/hid-transportmodnameN classnameN refexplicituh1hhh ubh)}(hhh]hKorean}(hhhhnubah}(h]h ]h"]h$]h&] refdomainh)reftypeh+ reftarget%/translations/ko_KR/hid/hid-transportmodnameN classnameN refexplicituh1hhh ubh)}(hhh]hSpanish}(hhhhubah}(h]h ]h"]h$]h&] refdomainh)reftypeh+ reftarget%/translations/sp_SP/hid/hid-transportmodnameN classnameN refexplicituh1hhh ubeh}(h]h ]h"]h$]h&]current_languageEnglishuh1h hh _documenthsourceNlineNubhsection)}(hhh](htitle)}(hHID I/O Transport Driversh]hHID I/O Transport Drivers}(hhhhhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhhh?/var/lib/git/docbuild/linux/Documentation/hid/hid-transport.rsthKubh paragraph)}(hXThe HID subsystem is independent of the underlying transport driver. Initially, only USB was supported, but other specifications adopted the HID design and provided new transport drivers. The kernel includes at least support for USB, Bluetooth, I2C and user-space I/O drivers.h]hXThe HID subsystem is independent of the underlying transport driver. Initially, only USB was supported, but other specifications adopted the HID design and provided new transport drivers. The kernel includes at least support for USB, Bluetooth, I2C and user-space I/O drivers.}(hhhhhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhhhhubh)}(hhh](h)}(h 1) HID Bush]h 1) HID Bus}(hhhhhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhhhhhK ubh)}(hXThe HID subsystem is designed as a bus. Any I/O subsystem may provide HID devices and register them with the HID bus. HID core then loads generic device drivers on top of it. The transport drivers are responsible for raw data transport and device setup/management. HID core is responsible for report-parsing, report interpretation and the user-space API. Device specifics and quirks are handled by all layers depending on the quirk.h]hXThe HID subsystem is designed as a bus. Any I/O subsystem may provide HID devices and register them with the HID bus. HID core then loads generic device drivers on top of it. The transport drivers are responsible for raw data transport and device setup/management. HID core is responsible for report-parsing, report interpretation and the user-space API. Device specifics and quirks are handled by all layers depending on the quirk.}(hhhhhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK hhhhubh literal_block)}(hX+-----------+ +-----------+ +-----------+ +-----------+ | Device #1 | | Device #i | | Device #j | | Device #k | +-----------+ +-----------+ +-----------+ +-----------+ \\ // \\ // +------------+ +------------+ | I/O Driver | | I/O Driver | +------------+ +------------+ || || +------------------+ +------------------+ | Transport Driver | | Transport Driver | +------------------+ +------------------+ \___ ___/ \ / +----------------+ | HID Core | +----------------+ / | | \ / | | \ ____________/ | | \_________________ / | | \ / | | \ +----------------+ +-----------+ +------------------+ +------------------+ | Generic Driver | | MT Driver | | Custom Driver #1 | | Custom Driver #2 | +----------------+ +-----------+ +------------------+ +------------------+h]hX+-----------+ +-----------+ +-----------+ +-----------+ | Device #1 | | Device #i | | Device #j | | Device #k | +-----------+ +-----------+ +-----------+ +-----------+ \\ // \\ // +------------+ +------------+ | I/O Driver | | I/O Driver | +------------+ +------------+ || || +------------------+ +------------------+ | Transport Driver | | Transport Driver | +------------------+ +------------------+ \___ ___/ \ / +----------------+ | HID Core | +----------------+ / | | \ / | | \ ____________/ | | \_________________ / | | \ / | | \ +----------------+ +-----------+ +------------------+ +------------------+ | Generic Driver | | MT Driver | | Custom Driver #1 | | Custom Driver #2 | +----------------+ +-----------+ +------------------+ +------------------+}(hhhhubah}(h]h ]h"]h$]h&] xml:spacepreserveuh1hhhhKhhhhubh)}(hExample Drivers:h]hExample Drivers:}(hhhhhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK/hhhhubh block_quote)}(hhh]h bullet_list)}(hhh](h list_item)}(hI/O: USB, I2C, Bluetooth-l2caph]h)}(hjh]hI/O: USB, I2C, Bluetooth-l2cap}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK1hjubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(h%Transport: USB-HID, I2C-HID, BT-HIDP h]h)}(h$Transport: USB-HID, I2C-HID, BT-HIDPh]h$Transport: USB-HID, I2C-HID, BT-HIDP}(hj/hj-hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK2hj)ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]bullet-uh1j hhhK1hjubah}(h]h ]h"]h$]h&]uh1jhhhhhNhNubh)}(hEverything below "HID Core" is simplified in this graph as it is only of interest to HID device drivers. Transport drivers do not need to know the specifics.h]hEverything below “HID Core” is simplified in this graph as it is only of interest to HID device drivers. Transport drivers do not need to know the specifics.}(hjQhjOhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK4hhhhubh)}(hhh](h)}(h1.1) Device Setuph]h1.1) Device Setup}(hjbhj`hhhNhNubah}(h]h ]h"]h$]h&]uh1hhj]hhhhhK9ubh)}(hXI/O drivers normally provide hotplug detection or device enumeration APIs to the transport drivers. Transport drivers use this to find any suitable HID device. They allocate HID device objects and register them with HID core. Transport drivers are not required to register themselves with HID core. HID core is never aware of which transport drivers are available and is not interested in it. It is only interested in devices.h]hXI/O drivers normally provide hotplug detection or device enumeration APIs to the transport drivers. Transport drivers use this to find any suitable HID device. They allocate HID device objects and register them with HID core. Transport drivers are not required to register themselves with HID core. HID core is never aware of which transport drivers are available and is not interested in it. It is only interested in devices.}(hjphjnhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK;hj]hhubh)}(hTransport drivers attach a constant "struct hid_ll_driver" object with each device. Once a device is registered with HID core, the callbacks provided via this struct are used by HID core to communicate with the device.h]hTransport drivers attach a constant “struct hid_ll_driver” object with each device. Once a device is registered with HID core, the callbacks provided via this struct are used by HID core to communicate with the device.}(hj~hj|hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKBhj]hhubh)}(hXHTransport drivers are responsible for detecting device failures and unplugging. HID core will operate a device as long as it is registered regardless of any device failures. Once transport drivers detect unplug or failure events, they must unregister the device from HID core and HID core will stop using the provided callbacks.h]hXHTransport drivers are responsible for detecting device failures and unplugging. HID core will operate a device as long as it is registered regardless of any device failures. Once transport drivers detect unplug or failure events, they must unregister the device from HID core and HID core will stop using the provided callbacks.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKFhj]hhubeh}(h] device-setupah ]h"]1.1) device setupah$]h&]uh1hhhhhhhhK9ubh)}(hhh](h)}(h"1.2) Transport Driver Requirementsh]h"1.2) Transport Driver Requirements}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhjhhhhhKMubh)}(hXThe terms "asynchronous" and "synchronous" in this document describe the transmission behavior regarding acknowledgements. An asynchronous channel must not perform any synchronous operations like waiting for acknowledgements or verifications. Generally, HID calls operating on asynchronous channels must be running in atomic-context just fine. On the other hand, synchronous channels can be implemented by the transport driver in whatever way they like. They might just be the same as asynchronous channels, but they can also provide acknowledgement reports, automatic retransmission on failure, etc. in a blocking manner. If such functionality is required on asynchronous channels, a transport-driver must implement that via its own worker threads.h]hXThe terms “asynchronous” and “synchronous” in this document describe the transmission behavior regarding acknowledgements. An asynchronous channel must not perform any synchronous operations like waiting for acknowledgements or verifications. Generally, HID calls operating on asynchronous channels must be running in atomic-context just fine. On the other hand, synchronous channels can be implemented by the transport driver in whatever way they like. They might just be the same as asynchronous channels, but they can also provide acknowledgement reports, automatic retransmission on failure, etc. in a blocking manner. If such functionality is required on asynchronous channels, a transport-driver must implement that via its own worker threads.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKOhjhhubh)}(hXHID core requires transport drivers to follow a given design. A Transport driver must provide two bi-directional I/O channels to each HID device. These channels must not necessarily be bi-directional in the hardware itself. A transport driver might just provide 4 uni-directional channels. Or it might multiplex all four on a single physical channel. However, in this document we will describe them as two bi-directional channels as they have several properties in common.h]hXHID core requires transport drivers to follow a given design. A Transport driver must provide two bi-directional I/O channels to each HID device. These channels must not necessarily be bi-directional in the hardware itself. A transport driver might just provide 4 uni-directional channels. Or it might multiplex all four on a single physical channel. However, in this document we will describe them as two bi-directional channels as they have several properties in common.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK[hjhhubj)}(hhh]j )}(hhh](j)}(hXInterrupt Channel (intr): The intr channel is used for asynchronous data reports. No management commands or data acknowledgements are sent on this channel. Any unrequested incoming or outgoing data report must be sent on this channel and is never acknowledged by the remote side. Devices usually send their input events on this channel. Outgoing events are normally not sent via intr, except if high throughput is required.h]h)}(hXInterrupt Channel (intr): The intr channel is used for asynchronous data reports. No management commands or data acknowledgements are sent on this channel. Any unrequested incoming or outgoing data report must be sent on this channel and is never acknowledged by the remote side. Devices usually send their input events on this channel. Outgoing events are normally not sent via intr, except if high throughput is required.h]hXInterrupt Channel (intr): The intr channel is used for asynchronous data reports. No management commands or data acknowledgements are sent on this channel. Any unrequested incoming or outgoing data report must be sent on this channel and is never acknowledged by the remote side. Devices usually send their input events on this channel. Outgoing events are normally not sent via intr, except if high throughput is required.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKchjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hXControl Channel (ctrl): The ctrl channel is used for synchronous requests and device management. Unrequested data input events must not be sent on this channel and are normally ignored. Instead, devices only send management events or answers to host requests on this channel. The control-channel is used for direct blocking queries to the device independent of any events on the intr-channel. Outgoing reports are usually sent on the ctrl channel via synchronous SET_REPORT requests. h]h)}(hXControl Channel (ctrl): The ctrl channel is used for synchronous requests and device management. Unrequested data input events must not be sent on this channel and are normally ignored. Instead, devices only send management events or answers to host requests on this channel. The control-channel is used for direct blocking queries to the device independent of any events on the intr-channel. Outgoing reports are usually sent on the ctrl channel via synchronous SET_REPORT requests.h]hXControl Channel (ctrl): The ctrl channel is used for synchronous requests and device management. Unrequested data input events must not be sent on this channel and are normally ignored. Instead, devices only send management events or answers to host requests on this channel. The control-channel is used for direct blocking queries to the device independent of any events on the intr-channel. Outgoing reports are usually sent on the ctrl channel via synchronous SET_REPORT requests.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKihjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]jGjHuh1j hhhKchjubah}(h]h ]h"]h$]h&]uh1jhjhhhNhNubh)}(hqCommunication between devices and HID core is mostly done via HID reports. A report can be of one of three types:h]hqCommunication between devices and HID core is mostly done via HID reports. A report can be of one of three types:}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKrhjhhubj)}(hhh]j )}(hhh](j)}(hX.INPUT Report: Input reports provide data from device to host. This data may include button events, axis events, battery status or more. This data is generated by the device and sent to the host with or without requiring explicit requests. Devices can choose to send data continuously or only on change.h]h)}(hX.INPUT Report: Input reports provide data from device to host. This data may include button events, axis events, battery status or more. This data is generated by the device and sent to the host with or without requiring explicit requests. Devices can choose to send data continuously or only on change.h]hX.INPUT Report: Input reports provide data from device to host. This data may include button events, axis events, battery status or more. This data is generated by the device and sent to the host with or without requiring explicit requests. Devices can choose to send data continuously or only on change.}(hj)hj'hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKuhj#ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hX;OUTPUT Report: Output reports change device states. They are sent from host to device and may include LED requests, rumble requests or more. Output reports are never sent from device to host, but a host can retrieve their current state. Hosts may choose to send output reports either continuously or only on change.h]h)}(hX;OUTPUT Report: Output reports change device states. They are sent from host to device and may include LED requests, rumble requests or more. Output reports are never sent from device to host, but a host can retrieve their current state. Hosts may choose to send output reports either continuously or only on change.h]hX;OUTPUT Report: Output reports change device states. They are sent from host to device and may include LED requests, rumble requests or more. Output reports are never sent from device to host, but a host can retrieve their current state. Hosts may choose to send output reports either continuously or only on change.}(hjAhj?hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKzhj;ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hXFEATURE Report: Feature reports are used for specific static device features and never reported spontaneously. A host can read and/or write them to access data like battery-state or device-settings. Feature reports are never sent without requests. A host must explicitly set or retrieve a feature report. This also means, feature reports are never sent on the intr channel as this channel is asynchronous. h]h)}(hXFEATURE Report: Feature reports are used for specific static device features and never reported spontaneously. A host can read and/or write them to access data like battery-state or device-settings. Feature reports are never sent without requests. A host must explicitly set or retrieve a feature report. This also means, feature reports are never sent on the intr channel as this channel is asynchronous.h]hXFEATURE Report: Feature reports are used for specific static device features and never reported spontaneously. A host can read and/or write them to access data like battery-state or device-settings. Feature reports are never sent without requests. A host must explicitly set or retrieve a feature report. This also means, feature reports are never sent on the intr channel as this channel is asynchronous.}(hjYhjWhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjSubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]jGjHuh1j hhhKuhjubah}(h]h ]h"]h$]h&]uh1jhjhhhNhNubh)}(hXgINPUT and OUTPUT reports can be sent as pure data reports on the intr channel. For INPUT reports this is the usual operational mode. But for OUTPUT reports, this is rarely done as OUTPUT reports are normally quite scarce. But devices are free to make excessive use of asynchronous OUTPUT reports (for instance, custom HID audio speakers make great use of it).h]hXgINPUT and OUTPUT reports can be sent as pure data reports on the intr channel. For INPUT reports this is the usual operational mode. But for OUTPUT reports, this is rarely done as OUTPUT reports are normally quite scarce. But devices are free to make excessive use of asynchronous OUTPUT reports (for instance, custom HID audio speakers make great use of it).}(hjyhjwhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubh)}(hPlain reports must not be sent on the ctrl channel, though. Instead, the ctrl channel provides synchronous GET/SET_REPORT requests. Plain reports are only allowed on the intr channel and are the only means of data there.h]hPlain reports must not be sent on the ctrl channel, though. Instead, the ctrl channel provides synchronous GET/SET_REPORT requests. Plain reports are only allowed on the intr channel and are the only means of data there.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubj)}(hhh]j )}(hhh](j)}(hXGET_REPORT: A GET_REPORT request has a report ID as payload and is sent from host to device. The device must answer with a data report for the requested report ID on the ctrl channel as a synchronous acknowledgement. Only one GET_REPORT request can be pending for each device. This restriction is enforced by HID core as several transport drivers don't allow multiple simultaneous GET_REPORT requests. Note that data reports which are sent as answer to a GET_REPORT request are not handled as generic device events. That is, if a device does not operate in continuous data reporting mode, an answer to GET_REPORT does not replace the raw data report on the intr channel on state change. GET_REPORT is only used by custom HID device drivers to query device state. Normally, HID core caches any device state so this request is not necessary on devices that follow the HID specs except during device initialization to retrieve the current state. GET_REPORT requests can be sent for any of the 3 report types and shall return the current report state of the device. However, OUTPUT reports as payload may be blocked by the underlying transport driver if the specification does not allow them.h]h)}(hXGET_REPORT: A GET_REPORT request has a report ID as payload and is sent from host to device. The device must answer with a data report for the requested report ID on the ctrl channel as a synchronous acknowledgement. Only one GET_REPORT request can be pending for each device. This restriction is enforced by HID core as several transport drivers don't allow multiple simultaneous GET_REPORT requests. Note that data reports which are sent as answer to a GET_REPORT request are not handled as generic device events. That is, if a device does not operate in continuous data reporting mode, an answer to GET_REPORT does not replace the raw data report on the intr channel on state change. GET_REPORT is only used by custom HID device drivers to query device state. Normally, HID core caches any device state so this request is not necessary on devices that follow the HID specs except during device initialization to retrieve the current state. GET_REPORT requests can be sent for any of the 3 report types and shall return the current report state of the device. However, OUTPUT reports as payload may be blocked by the underlying transport driver if the specification does not allow them.h]hXGET_REPORT: A GET_REPORT request has a report ID as payload and is sent from host to device. The device must answer with a data report for the requested report ID on the ctrl channel as a synchronous acknowledgement. Only one GET_REPORT request can be pending for each device. This restriction is enforced by HID core as several transport drivers don’t allow multiple simultaneous GET_REPORT requests. Note that data reports which are sent as answer to a GET_REPORT request are not handled as generic device events. That is, if a device does not operate in continuous data reporting mode, an answer to GET_REPORT does not replace the raw data report on the intr channel on state change. GET_REPORT is only used by custom HID device drivers to query device state. Normally, HID core caches any device state so this request is not necessary on devices that follow the HID specs except during device initialization to retrieve the current state. GET_REPORT requests can be sent for any of the 3 report types and shall return the current report state of the device. However, OUTPUT reports as payload may be blocked by the underlying transport driver if the specification does not allow them.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hXSET_REPORT: A SET_REPORT request has a report ID plus data as payload. It is sent from host to device and a device must update its current report state according to the given data. Any of the 3 report types can be used. However, INPUT reports as payload might be blocked by the underlying transport driver if the specification does not allow them. A device must answer with a synchronous acknowledgement. However, HID core does not require transport drivers to forward this acknowledgement to HID core. Same as for GET_REPORT, only one SET_REPORT can be pending at a time. This restriction is enforced by HID core as some transport drivers do not support multiple synchronous SET_REPORT requests. h]h)}(hXSET_REPORT: A SET_REPORT request has a report ID plus data as payload. It is sent from host to device and a device must update its current report state according to the given data. Any of the 3 report types can be used. However, INPUT reports as payload might be blocked by the underlying transport driver if the specification does not allow them. A device must answer with a synchronous acknowledgement. However, HID core does not require transport drivers to forward this acknowledgement to HID core. Same as for GET_REPORT, only one SET_REPORT can be pending at a time. This restriction is enforced by HID core as some transport drivers do not support multiple synchronous SET_REPORT requests.h]hXSET_REPORT: A SET_REPORT request has a report ID plus data as payload. It is sent from host to device and a device must update its current report state according to the given data. Any of the 3 report types can be used. However, INPUT reports as payload might be blocked by the underlying transport driver if the specification does not allow them. A device must answer with a synchronous acknowledgement. However, HID core does not require transport drivers to forward this acknowledgement to HID core. Same as for GET_REPORT, only one SET_REPORT can be pending at a time. This restriction is enforced by HID core as some transport drivers do not support multiple synchronous SET_REPORT requests.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]jGjHuh1j hhhKhjubah}(h]h ]h"]h$]h&]uh1jhjhhhNhNubh)}(hOther ctrl-channel requests are supported by USB-HID but are not available (or deprecated) in most other transport level specifications:h]hOther ctrl-channel requests are supported by USB-HID but are not available (or deprecated) in most other transport level specifications:}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubj)}(hhh]j )}(hhh](j)}(h/GET/SET_IDLE: Only used by USB-HID and I2C-HID.h]h)}(hjh]h/GET/SET_IDLE: Only used by USB-HID and I2C-HID.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(h'GET/SET_PROTOCOL: Not used by HID core.h]h)}(hjh]h'GET/SET_PROTOCOL: Not used by HID core.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(h2RESET: Used by I2C-HID, not hooked up in HID core.h]h)}(hjh]h2RESET: Used by I2C-HID, not hooked up in HID core.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(h7SET_POWER: Used by I2C-HID, not hooked up in HID core. h]h)}(h6SET_POWER: Used by I2C-HID, not hooked up in HID core.h]h6SET_POWER: Used by I2C-HID, not hooked up in HID core.}(hj4hj2hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj.ubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]jGjHuh1j hhhKhjubah}(h]h ]h"]h$]h&]uh1jhjhhhNhNubeh}(h]transport-driver-requirementsah ]h"]"1.2) transport driver requirementsah$]h&]uh1hhhhhhhhKMubeh}(h]hid-busah ]h"] 1) hid busah$]h&]uh1hhhhhhhhK ubh)}(hhh](h)}(h 2) HID APIh]h 2) HID API}(hjghjehhhNhNubah}(h]h ]h"]h$]h&]uh1hhjbhhhhhKubh)}(hhh](h)}(h2.1) Initializationh]h2.1) Initialization}(hjxhjvhhhNhNubah}(h]h ]h"]h$]h&]uh1hhjshhhhhKubh)}(h_Transport drivers normally use the following procedure to register a new device with HID core::h]h^Transport drivers normally use the following procedure to register a new device with HID core:}(h^Transport drivers normally use the following procedure to register a new device with HID core:hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjshhubh)}(hXstruct hid_device *hid; int ret; hid = hid_allocate_device(); if (IS_ERR(hid)) { ret = PTR_ERR(hid); goto err_<...>; } strscpy(hid->name, , sizeof(hid->name)); strscpy(hid->phys, , sizeof(hid->phys)); strscpy(hid->uniq, , sizeof(hid->uniq)); hid->ll_driver = &custom_ll_driver; hid->bus = ; hid->vendor = ; hid->product = ; hid->version = ; hid->country = ; hid->dev.parent = ; hid->driver_data = ; ret = hid_add_device(hid); if (ret) goto err_<...>;h]hXstruct hid_device *hid; int ret; hid = hid_allocate_device(); if (IS_ERR(hid)) { ret = PTR_ERR(hid); goto err_<...>; } strscpy(hid->name, , sizeof(hid->name)); strscpy(hid->phys, , sizeof(hid->phys)); strscpy(hid->uniq, , sizeof(hid->uniq)); hid->ll_driver = &custom_ll_driver; hid->bus = ; hid->vendor = ; hid->product = ; hid->version = ; hid->country = ; hid->dev.parent = ; hid->driver_data = ; ret = hid_add_device(hid); if (ret) goto err_<...>;}(hhhjubah}(h]h ]h"]h$]h&]hhuh1hhhhKhjshhubh)}(hOnce hid_add_device() is entered, HID core might use the callbacks provided in "custom_ll_driver". Note that fields like "country" can be ignored by underlying transport-drivers if not supported.h]hOnce hid_add_device() is entered, HID core might use the callbacks provided in “custom_ll_driver”. Note that fields like “country” can be ignored by underlying transport-drivers if not supported.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjshhubh)}(hTo unregister a device, use::h]hTo unregister a device, use:}(hTo unregister a device, use:hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjshhubh)}(hhid_destroy_device(hid);h]hhid_destroy_device(hid);}(hhhjubah}(h]h ]h"]h$]h&]hhuh1hhhhKhjshhubh)}(h\Once hid_destroy_device() returns, HID core will no longer make use of any driver callbacks.h]h\Once hid_destroy_device() returns, HID core will no longer make use of any driver callbacks.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjshhubeh}(h]initializationah ]h"]2.1) initializationah$]h&]uh1hhjbhhhhhKubh)}(hhh](h)}(h2.2) hid_ll_driver operationsh]h2.2) hid_ll_driver operations}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhjhhhhhKubh)}(h The available HID callbacks are:h]h The available HID callbacks are:}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubj)}(hhh](h)}(h&int (*start) (struct hid_device *hdev)h]h&int (*start) (struct hid_device *hdev)}(hhhjubah}(h]h ]h"]h$]h&]hhuh1hhhhKhjubh)}(hX Called from HID device drivers once they want to use the device. Transport drivers can choose to setup their device in this callback. However, normally devices are already set up before transport drivers register them to HID core so this is mostly only used by USB-HID.h]hX Called from HID device drivers once they want to use the device. Transport drivers can choose to setup their device in this callback. However, normally devices are already set up before transport drivers register them to HID core so this is mostly only used by USB-HID.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubh)}(h&void (*stop) (struct hid_device *hdev)h]h&void (*stop) (struct hid_device *hdev)}(hhhj ubah}(h]h ]h"]h$]h&]hhuh1hhhhKhjubh)}(hCalled from HID device drivers once they are done with a device. Transport drivers can free any buffers and deinitialize the device. But note that ->start() might be called again if another HID device driver is loaded on the device.h]hCalled from HID device drivers once they are done with a device. Transport drivers can free any buffers and deinitialize the device. But note that ->start() might be called again if another HID device driver is loaded on the device.}(hj0hj.hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubh)}(htTransport drivers are free to ignore it and deinitialize devices after they destroyed them via hid_destroy_device().h]htTransport drivers are free to ignore it and deinitialize devices after they destroyed them via hid_destroy_device().}(hj>hj<hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubh)}(h%int (*open) (struct hid_device *hdev)h]h%int (*open) (struct hid_device *hdev)}(hhhjJubah}(h]h ]h"]h$]h&]hhuh1hhhhMhjubh)}(hXqCalled from HID device drivers once they are interested in data reports. Usually, while user-space didn't open any input API/etc., device drivers are not interested in device data and transport drivers can put devices asleep. However, once ->open() is called, transport drivers must be ready for I/O. ->open() calls are nested for each client that opens the HID device.h]hXsCalled from HID device drivers once they are interested in data reports. Usually, while user-space didn’t open any input API/etc., device drivers are not interested in device data and transport drivers can put devices asleep. However, once ->open() is called, transport drivers must be ready for I/O. ->open() calls are nested for each client that opens the HID device.}(hjZhjXhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjubh)}(h'void (*close) (struct hid_device *hdev)h]h'void (*close) (struct hid_device *hdev)}(hhhjfubah}(h]h ]h"]h$]h&]hhuh1hhhhM hjubh)}(hCalled from HID device drivers after ->open() was called but they are no longer interested in device reports. (Usually if user-space closed any input devices of the driver).h]hCalled from HID device drivers after ->open() was called but they are no longer interested in device reports. (Usually if user-space closed any input devices of the driver).}(hjvhjthhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM hjubh)}(hTransport drivers can put devices asleep and terminate any I/O of all ->open() calls have been followed by a ->close() call. However, ->start() may be called again if the device driver is interested in input reports again.h]hTransport drivers can put devices asleep and terminate any I/O of all ->open() calls have been followed by a ->close() call. However, ->start() may be called again if the device driver is interested in input reports again.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjubh)}(h&int (*parse) (struct hid_device *hdev)h]h&int (*parse) (struct hid_device *hdev)}(hhhjubah}(h]h ]h"]h$]h&]hhuh1hhhhMhjubh)}(hCalled once during device setup after ->start() has been called. Transport drivers must read the HID report-descriptor from the device and tell HID core about it via hid_parse_report().h]hCalled once during device setup after ->start() has been called. Transport drivers must read the HID report-descriptor from the device and tell HID core about it via hid_parse_report().}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjubh)}(h1int (*power) (struct hid_device *hdev, int level)h]h1int (*power) (struct hid_device *hdev, int level)}(hhhjubah}(h]h ]h"]h$]h&]hhuh1hhhhMhjubh)}(hCalled by HID core to give PM hints to transport drivers. Usually this is analogical to the ->open() and ->close() hints and redundant.h]hCalled by HID core to give PM hints to transport drivers. Usually this is analogical to the ->open() and ->close() hints and redundant.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM!hjubh)}(hbvoid (*request) (struct hid_device *hdev, struct hid_report *report, int reqtype)h]hbvoid (*request) (struct hid_device *hdev, struct hid_report *report, int reqtype)}(hhhjubah}(h]h ]h"]h$]h&]hhuh1hhhhM&hjubh)}(hSend a HID request on the ctrl channel. "report" contains the report that should be sent and "reqtype" the request type. Request-type can be HID_REQ_SET_REPORT or HID_REQ_GET_REPORT.h]hSend a HID request on the ctrl channel. “report” contains the report that should be sent and “reqtype” the request type. Request-type can be HID_REQ_SET_REPORT or HID_REQ_GET_REPORT.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM)hjubh)}(hThis callback is optional. If not provided, HID core will assemble a raw report following the HID specs and send it via the ->raw_request() callback. The transport driver is free to implement this asynchronously.h]hThis callback is optional. If not provided, HID core will assemble a raw report following the HID specs and send it via the ->raw_request() callback. The transport driver is free to implement this asynchronously.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM-hjubh)}(h%int (*wait) (struct hid_device *hdev)h]h%int (*wait) (struct hid_device *hdev)}(hhhjubah}(h]h ]h"]h$]h&]hhuh1hhhhM3hjubh)}(hUsed by HID core before calling ->request() again. A transport driver can use it to wait for any pending requests to complete if only one request is allowed at a time.h]hUsed by HID core before calling ->request() again. A transport driver can use it to wait for any pending requests to complete if only one request is allowed at a time.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM5hjubh)}(hint (*raw_request) (struct hid_device *hdev, unsigned char reportnum, __u8 *buf, size_t count, unsigned char rtype, int reqtype)h]hint (*raw_request) (struct hid_device *hdev, unsigned char reportnum, __u8 *buf, size_t count, unsigned char rtype, int reqtype)}(hhhjubah}(h]h ]h"]h$]h&]hhuh1hhhhM;hjubh)}(hSame as ->request() but provides the report as raw buffer. This request shall be synchronous. A transport driver must not use ->wait() to complete such requests. This request is mandatory and hid core will reject the device if it is missing.h]hSame as ->request() but provides the report as raw buffer. This request shall be synchronous. A transport driver must not use ->wait() to complete such requests. This request is mandatory and hid core will reject the device if it is missing.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM?hjubh)}(hEint (*output_report) (struct hid_device *hdev, __u8 *buf, size_t len)h]hEint (*output_report) (struct hid_device *hdev, __u8 *buf, size_t len)}(hhhj*ubah}(h]h ]h"]h$]h&]hhuh1hhhhMFhjubh)}(hXSend raw output report via intr channel. Used by some HID device drivers which require high throughput for outgoing requests on the intr channel. This must not cause SET_REPORT calls! This must be implemented as asynchronous output report on the intr channel!h]hXSend raw output report via intr channel. Used by some HID device drivers which require high throughput for outgoing requests on the intr channel. This must not cause SET_REPORT calls! This must be implemented as asynchronous output report on the intr channel!}(hj:hj8hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMHhjubh)}(hHint (*idle) (struct hid_device *hdev, int report, int idle, int reqtype)h]hHint (*idle) (struct hid_device *hdev, int report, int idle, int reqtype)}(hhhjFubah}(h]h ]h"]h$]h&]hhuh1hhhhMOhjubh)}(hEPerform SET/GET_IDLE request. Only used by USB-HID, do not implement!h]hEPerform SET/GET_IDLE request. Only used by USB-HID, do not implement!}(hjVhjThhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMQhjubeh}(h]h ]h"]h$]h&]uh1jhjhhhhhNubeh}(h]hid-ll-driver-operationsah ]h"]2.2) hid_ll_driver operationsah$]h&]uh1hhjbhhhhhKubh)}(hhh](h)}(h2.3) Data Pathh]h2.3) Data Path}(hjuhjshhhNhNubah}(h]h ]h"]h$]h&]uh1hhjphhhhhMTubh)}(hX Transport drivers are responsible of reading data from I/O devices. They must handle any I/O-related state-tracking themselves. HID core does not implement protocol handshakes or other management commands which can be required by the given HID transport specification.h]hX Transport drivers are responsible of reading data from I/O devices. They must handle any I/O-related state-tracking themselves. HID core does not implement protocol handshakes or other management commands which can be required by the given HID transport specification.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMVhjphhubh)}(hEvery raw data packet read from a device must be fed into HID core via hid_input_report(). You must specify the channel-type (intr or ctrl) and report type (input/output/feature). Under normal conditions, only input reports are provided via this API.h]hEvery raw data packet read from a device must be fed into HID core via hid_input_report(). You must specify the channel-type (intr or ctrl) and report type (input/output/feature). Under normal conditions, only input reports are provided via this API.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM[hjphhubh)}(hX Responses to GET_REPORT requests via ->request() must also be provided via this API. Responses to ->raw_request() are synchronous and must be intercepted by the transport driver and not passed to hid_input_report(). Acknowledgements to SET_REPORT requests are not of interest to HID core.h]hX Responses to GET_REPORT requests via ->request() must also be provided via this API. Responses to ->raw_request() are synchronous and must be intercepted by the transport driver and not passed to hid_input_report(). Acknowledgements to SET_REPORT requests are not of interest to HID core.}(hjhjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM`hjphhubh transition)}(h4----------------------------------------------------h]h}(h]h ]h"]h$]h&]uh1jhhhMehjphhubh)}(h4Written 2013, David Herrmann h](hWritten 2013, David Herrmann <}(hWritten 2013, David Herrmann }(h>hjhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhMghjphhubeh}(h] data-pathah ]h"]2.3) data pathah$]h&]uh1hhjbhhhhhMTubeh}(h]hid-apiah ]h"] 2) hid apiah$]h&]uh1hhhhhhhhKubeh}(h]hid-i-o-transport-driversah ]h"]hid i/o transport driversah$]h&]uh1hhhhhhhhKubeh}(h]h ]h"]h$]h&]sourcehuh1hcurrent_sourceN current_lineNsettingsdocutils.frontendValues)}(hN generatorN datestampN source_linkN source_urlN toc_backlinksentryfootnote_backlinksK sectnum_xformKstrip_commentsNstrip_elements_with_classesN strip_classesN report_levelK halt_levelKexit_status_levelKdebugNwarning_streamN tracebackinput_encoding utf-8-siginput_encoding_error_handlerstrictoutput_encodingutf-8output_encoding_error_handlerjerror_encodingUTF-8error_encoding_error_handlerbackslashreplace language_codeenrecord_dependenciesNconfigN id_prefixhauto_id_prefixid dump_settingsNdump_internalsNdump_transformsNdump_pseudo_xmlNexpose_internalsNstrict_visitorN_disable_configN_sourceh _destinationN _config_files]7/var/lib/git/docbuild/linux/Documentation/docutils.confapep_referencesN pep_base_urlhttps://peps.python.org/pep_file_url_templatepep-%04drfc_referencesN rfc_base_url&https://datatracker.ietf.org/doc/html/ tab_widthKtrim_footnote_reference_spacefile_insertion_enabled raw_enabledKline_length_limitM'syntax_highlightlong smart_quotessmartquotes_locales]character_level_inline_markupdoctitle_xform docinfo_xformKsectsubtitle_xform image_loadinglinkembed_stylesheetcloak_email_addressessection_self_link embed_imagesenvNubreporterNindirect_targets]substitution_defs}substitution_names}refnames}refids}nameids}(jjj_j\jjjWjTjjjjjmjjjju nametypes}(jNj_NjNjWNjNjNjmNjNuh}(jhj\hjj]jTjjjbjjsjjjjjpu footnote_refs} citation_refs} autofootnotes]autofootnote_refs]symbol_footnotes]symbol_footnote_refs] footnotes] citations]autofootnote_startKsymbol_footnote_startK id_counter collectionsCounter}Rparse_messages]transform_messages] transformerN include_log] decorationNhhub.