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

@page page_device_input_dm Input device model (DM)

Input subsystem under RT_USING_DM

The input core (components/drivers/input/input.c) is built only when RT_USING_INPUT is enabled. That Kconfig option depends on RT_USING_DM — there is no legacy non-DM input stack in-tree. Drivers publish Linux-style EV_* events through struct rt_input_device; consumers attach via rt_input_add_handler or POSIX /dev/inputN (@ref page_device_input_uapi).

Event reporting API, polling rules, and pitfalls: @ref page_device_input.

Topic	Page
Userspace open/read/ioctl	@ref page_device_input_uapi
rt_touch_device bridge	@ref page_device_input_touch
KEY_POWER / KEY_RESTART shutdown/reset	@ref page_device_input_power

Sources:

File	Role
input.c	Global device list, rt_dm_ida naming (input0…), rt_input_device_register
input_power.c	@ref page_device_input_power
input_touch.c	@ref page_device_input_touch
input_uapi.c	@ref page_device_input_uapi
keyboard/, joystick/, touchscreen/, misc/	OFW platform/SPI drivers

---

Kconfig / build

Option	Role
RT_USING_DM	Parent — input cannot be enabled without DM
RT_USING_INPUT	Core input.c; selects RT_USING_ADT + bitmap ADT
RT_INPUT_POWER	@ref page_device_input_power (default y)
RT_INPUT_UAPI	@ref page_device_input_uapi
RT_INPUT_KEYBOARD	gpio-keys, adc-keys (see sub-options)
RT_INPUT_JOYSTICK	adc-joystick
RT_INPUT_TOUCHSCREEN	@ref page_device_input_touch
RT_INPUT_MISC	e.g. ettus,e3x0-button
SOC_DM_INPUT_*_DIR	BSP adds more platform drivers via osource in sub-Kconfig

Unlike @ref page_device_i2c_dm, input has no dedicated rt_bus. Each hardware block is a normal struct rt_platform_driver (or struct rt_spi_driver) that embeds or owns struct rt_input_device and calls rt_input_device_register from probe.

---

Architecture

  Device tree node (compatible = "gpio-keys", "adc-keys", …)
        |
        |  platform bus match (rt_ofw_node_id) or SPI bus match
        v
  driver probe(pdev)
        |
        |  parse OFW (gpios, io-channels, irq, …)
        |  rt_input_set_capability(idev, EV_KEY|EV_ABS, code)
        |  optional: rt_input_setup_polling / rt_input_setup_touch
        v
  rt_input_device_register(idev)
        |
        |  rt_dm_ida_alloc → name "inputN"
        |  rt_device_register (RT_Device_Class_Char, DEACTIVATE)
        |  [RT_INPUT_UAPI] input_uapi_init
        |  list on input_device_nodes
        v
  [RT_INPUT_TOUCHSCREEN] input_touch_register → rt_touch_device
  [RT_INPUT_POWER]       global KEY_POWER / KEY_RESTART handlers
        |
        v
  Hardware IRQ / timer poll → rt_input_report_* → rt_input_sync
        |
        v
  rt_input_event → handlers / UAPI queue

Layer	Object	Notes
Input device	struct rt_input_device	Embeds struct rt_device parent; capabilities in bitmaps
DM naming	input_ida in input.c	rt_dm_dev_set_name(&idev->parent, "input%u", id)
Platform binding	RT_PLATFORM_DRIVER_EXPORT	Probe/remove on struct rt_platform_device
SPI touch	RT_SPI_DRIVER_EXPORT	e.g. ADS7846 — see @ref page_device_input_touch

---

Core registration (input.c)

rt_err_t rt_input_device_register(struct rt_input_device *idev);
rt_err_t rt_input_device_unregister(struct rt_input_device *idev);

Step	Behavior
Allocate ID	rt_dm_ida_alloc(&input_ida) — failure → -RT_EFULL
Init lists / lock	Per-device handler_nodes, rt_spinlock
Register char dev	RT_Device_Class_Char, flag RT_DEVICE_FLAG_DEACTIVATE
Post-register	Start poller timer if idev->poller; input_touch_register; UAPI fops if enabled
Unregister	Refcount check; UAPI/touch teardown; rt_dm_ida_free

Driver pattern — embed input at a known offset:

struct my_input {
    struct rt_input_device parent;
    /* private */
};

static void my_report(struct my_input *mi)
{
    rt_input_report_key(&mi->parent, KEY_ENTER, 1);
    rt_input_sync(&mi->parent);
}

Use rt_container_of(idev, struct my_input, parent) in poll/IRQ callbacks.

---

In-tree OFW drivers

Compatible / binding	Driver file	Bus	Summary
gpio-keys	keyboard/keys-gpio.c	platform	Parent node; each child → one inputN per key
adc-keys	keyboard/keys-adc.c	platform	io-channels via @ref page_device_iio_dm; polling
adc-joystick	joystick/js-adc.c	platform	Per-child reg, IIO, EV_ABS polling
ti,ads7846 … ti,xpt2046	touchscreen/ts-ads7846.c	SPI	@ref page_device_input_touch
ettus,e3x0-button	misc/button-e3x0.c	platform	IRQ press/release → KEY_POWER

gpio-keys (platform + children)

• Parent compatible = "gpio-keys"; subnodes are individual buttons.
• Each child: rt_ofw_get_named_pin, property matching *,code$ (e.g. linux,code), optional debounce-interval.
• One rt_input_device per child (not one device for the whole parent).

adc-keys / adc-joystick (IIO consumers)

• Resolve ADC through rt_iio_channel_get_by_name / rt_iio_channel_get_by_index (@ref page_device_iio_dm).
• Default poll-interval 200 ms if property missing.

ADS7846 family (SPI)

• RT_SPI_DRIVER_EXPORT(ads7846_driver); regulator, IRQ, worker thread.
• DT axis/touch properties consumed by input_touch_parse — @ref page_device_input_touch.

---

Device tree examples

GPIO key (child node)

gpio-keys {
    compatible = "gpio-keys";

    power-key {
        label = "Power";
        gpios = <&gpio0 5 GPIO_ACTIVE_LOW>;
        linux,code = <116>;   /* KEY_POWER — see page_device_input_power */
        debounce-interval = <15>;
    };
};

ADC resistor ladder

adc-keys {
    compatible = "adc-keys";
    io-channels = <&saradc 0>;
    io-channel-names = "buttons";
    poll-interval = <100>;
    keyup-threshold-microvolt = <1800000>;

    up {
        press-threshold-microvolt = <500000>;
        linux,code = <103>;   /* KEY_UP */
    };
};

SPI resistive touch

touch: touchscreen@0 {
    compatible = "ti,ads7846";
    reg = <0>;
    interrupt-parent = <&gpio1>;
    interrupts = <25 IRQ_TYPE_EDGE_FALLING>;
    ti,x-min = /bits/ 16 <0>;
    ti,x-max = /bits/ 16 <4095>;
    ti,y-min = /bits/ 16 <0>;
    ti,y-max = /bits/ 16 <4095>;
    vcc-supply = <&reg_3v3>;
};

(SPI reg / spi-max-frequency belong on the child under the SPI controller node per your BSP.)

---

New platform input driver checklist

1. Enable RT_USING_DM, RT_USING_OFW, RT_USING_INPUT (and subsystem menu if you add under keyboard/ etc.).
2. struct rt_platform_driver with ofw_ids[] matching Linux binding where possible.
3. In probe: allocate driver private struct with struct rt_input_device embedded first (or pointer field).
4. rt_input_set_capability for every type/code you will report; for EV_ABS, call rt_input_set_absinfo (after capability allocates absinfo).
5. IRQ or rt_input_setup_polling — poller poll must not block (@ref page_device_input).
6. On each logical event frame: rt_input_report_* then rt_input_sync.
7. rt_input_device_register only when hardware is ready; store private data in pdev->parent.user_data or rt_ofw_data(np) for remove.
8. remove: stop IRQ/poller, rt_input_device_unregister, free memory.
9. RT_PLATFORM_DRIVER_EXPORT(drv) (or RT_SPI_DRIVER_EXPORT on SPI slaves).

---

Pitfalls

Issue	Mitigation
Missing rt_input_sync	Consumers see partial frames — always end with rt_input_sync.
Capability after register	Set capabilities before rt_input_device_register.
EV_ABS without absinfo	Call rt_input_set_capability(EV_ABS, axis) then rt_input_set_absinfo.
Unregister with open UAPI fd	Close /dev/inputN first — @ref page_device_input_uapi
gpio-keys child vs parent	Driver registers per child; do not expect one input0 for the whole node.
IIO channel NULL	Fix DT io-channels — @ref page_device_iio_dm
Power handler surprise	@ref page_device_input_power

---

See also

• @ref page_device_input
• @ref page_device_input_uapi
• @ref page_device_input_touch
• @ref page_device_input_power
• @ref page_device_iio_dm
• @ref page_device_bus
• components/drivers/include/drivers/input.h
• components/drivers/input/Kconfig