Documentation/hid/hid-transport.rst

15 drivers on top of it. The transport drivers are responsible of raw data
18 and quirks are handled by all layers depending on the quirk.
62 drivers are not required to register themselves with HID core. HID core is never
63 aware of which transport drivers are available and is not interested in it. It
68 this struct are used by HID core to communicate with the device.
70 Transport drivers are responsible of detecting device failures and unplugging.
100    reports. No management commands or data acknowledgements are sent on this
103    send their input events on this channel. Outgoing events are normally
107    channel and are normally ignored. Instead, devices only send management
111    Outgoing reports are usually sent on the ctrl channel via synchronous
122  - OUTPUT Report: Output reports change device states. They are sent from host
124    reports are never sent from device to host, but a host can retrieve their
128  - FEATURE Report: Feature reports are used for specific static device features
131    Feature reports are never sent without requests. A host must explicitly set
132    or retrieve a feature report. This also means, feature reports are never sent
137 this is rarely done as OUTPUT reports are normally quite scarce. But devices are
142 channel provides synchronous GET/SET_REPORT requests. Plain reports are only
143 allowed on the intr channel and are the only means of data there.
151    Note that data reports which are sent as answer to a GET_REPORT request are
175 Other ctrl-channel requests are supported by USB-HID but are not available
232 The available HID callbacks are:
240    devices are already set up before transport drivers register them to HID core
247    Called from HID device drivers once they are done with a device. Transport
252    Transport drivers are free to ignore it and deinitialize devices after they
259    Called from HID device drivers once they are interested in data reports.
260    Usually, while user-space didn't open any input API/etc., device drivers are
263    ->open() calls are nested for each client that opens the HID device.
269    Called from HID device drivers after ->open() was called but they are no
342 Transport drivers are responsible of reading data from I/O devices. They must
349 type (input/output/feature). Under normal conditions, only input reports are
353 API. Responses to ->raw_request() are synchronous and must be intercepted by the
355 Acknowledgements to SET_REPORT requests are not of interest to HID core.