rt-thread/documentation/6.components/device-driver/input/input.md

@page page_device_input Input subsystem

Device-tree binding and DM registration: @ref page_device_input_dm.

Topic	Page
Userspace API	@ref page_device_input_uapi
Touch class bridge	@ref page_device_input_touch
Power / restart keys	@ref page_device_input_power

Input subsystem (API)

Header: drivers/input.h. Typical stack: low-level driver → rt_input_event / reporters → handlers (GUI, shell) or /dev/inputN (@ref page_device_input_uapi).

Path	API
In-kernel listener	rt_input_add_handler
POSIX process (Smart)	open / read / ioctl / poll on /dev/inputN — @ref page_device_input_uapi
Legacy touch GUI	struct rt_touch_device — @ref page_device_input_touch

When to use the input core

Use rt_input_* when…	Consider raw rt_device read when…
You want Linux-like EV_KEY / EV_REL / EV_ABS / multitouch slot semantics and multiple listeners.	You have a single proprietary app talking to a vendor IOCTL-only touch stack.
You need polling (**rt_input_setup_polling**) for GPIO keys without IRQ storms.	GPIO IRQ latency is fine and you do not need unified event routing.

Event contract

1. rt_input_set_capability before rt_input_device_register so users know which type/code pairs are valid.
2. For each hardware change, call rt_input_report_* then rt_input_sync to close the frame (SYN_REPORT). Missing sync merges events poorly for consumers.
3. rt_input_trigger routes through optional idev->trigger—use when you wrap another input device; otherwise rt_input_event is enough.

Callback / context rules

• rt_input_add_handler → callback: invoked from rt_input_event path—assume thread or workqueue unless your driver documents IRQ delivery; keep callback short.
• poller->poll: runs on timer tick—must not block or take mutexes that can deadlock with the same thread calling rt_input_sync.
• Touch helpers: rt_input_setup_touch / rt_input_report_touch_* require RT_INPUT_TOUCHSCREEN — @ref page_device_input_touch.

Registration lifecycle

• rt_input_device_register: registers underlying rt_device; failures leave partially init state—clean up partial setup in error paths.
• rt_input_remove_config: tears down polling/touch dynamic config before unregister if you toggled features at runtime.

Pitfalls

• ABS without rt_input_set_absinfo: consumers cannot clamp—set min/max/resolution for axes you report.
• Key autorepeat: not automatic unless a layer implements it—do not assume Linux repeat behavior.
• Re-entrancy: posting events from inside a handler for the same device can recurse—prefer queueing.

See also

• @ref page_device_input_dm
• @ref page_device_input_uapi
• @ref page_device_input_touch
• @ref page_device_input_power
• components/drivers/include/drivers/input.h
• components/drivers/include/drivers/input_uapi.h
• dt-bindings/input/event-codes.h