Touch bridge (`RT_INPUT_TOUCHSCREEN`)

input_touch.c bridges struct rt_input_device (Linux-style EV_ABS / multitouch slots) to struct rt_touch_device so GUI stacks can use the legacy touch class API (rt_device_find, RT_TOUCH_CTRL_*, rt_hw_touch_isr) without duplicating panel drivers.

Input core and OFW drivers (e.g. ADS7846): @ref page_device_input_dm. Event helpers (rt_input_setup_touch, rt_input_report_touch_*): @ref page_device_input.

Sources: components/drivers/input/input_touch.c, components/drivers/input/touchscreen/.

Kconfig

Option	Role
`RT_INPUT_TOUCHSCREEN`	Build `input_touch.c`; selects `RT_USING_TOUCH`
`RT_INPUT_TOUCHSCREEN_ADS7846`	In-tree SPI resistive driver `ts-ads7846.c`
`SOC_DM_INPUT_TOUCHSCREEN_DIR`	BSP adds more panel drivers

Requires RT_USING_INPUT and RT_USING_DM.

Architecture

  Panel driver (e.g. ads7846)
        |
        |  rt_input_set_capability(EV_ABS, …)
        |  rt_input_setup_touch(idev, num_slots, &touch_info)
        |  rt_input_device_register(idev)
        v
  input_touch_register (after idev on global list)
        |
        |  rt_hw_touch_register → device "touchN"
        |  rt_input_add_handler → input_touch_cb
        v
  Driver reports: rt_input_report_touch_* / rt_input_sync
        |
        v
  input_touch_cb: EV_ABS → struct rt_touch_data
                  SYN_REPORT → rt_hw_touch_isr()
        |
        v
  GUI: rt_device_read / touch ISR callback

Object	Role
`struct input_touch_properties`	Stored in `idev->touch`: DT-derived min/max, invert, swap, slot count
`struct input_touch_device`	Embeds `struct rt_touch_device` + `rt_input_handler` + per-slot `rt_touch_data`
`input_touch_ops`	`touch_readpoint`, `touch_control` (range, enable/disable, status)

input_touch_register only creates the rt_touch_device when rt_input_setup_touch was called with non-NULL struct rt_touch_info *info ( prop->touch_dev allocated).

Driver API (`input.h`)

rt_err_t rt_input_setup_touch(struct rt_input_device *idev,
        rt_uint32_t num_slots, struct rt_touch_info *info);
rt_err_t rt_input_parse_touch_position(struct rt_input_device *idev,
        rt_uint32_t *out_x, rt_uint32_t *out_y);
rt_bool_t rt_input_report_touch_inactive(struct rt_input_device *idev, rt_bool_t active);
void rt_input_report_touch_position(struct rt_input_device *idev,
        rt_uint32_t x, rt_uint32_t y, rt_bool_t multitouch);

API	Role
`rt_input_setup_touch`	Allocate `idev->touch`, parse DT, optional multitouch absinfo (`ABS_MT_SLOT`, `ABS_MT_TRACKING_ID`)
`num_slots == 0`	Single-touch (`ABS_X`/`ABS_Y`); `num_slots > 0`
`rt_input_report_touch_position`	Apply invert/swap from DT, then `rt_input_report_abs`
`rt_input_report_touch_inactive`	Emit `ABS_MT_TRACKING_ID = -1` on release
`rt_input_parse_touch_position`	Map raw x/y through *`touchscreen-inverted-` / `touchscreen-swapped-x-y`**

Call rt_input_setup_touch before rt_input_device_register. input_touch_register runs inside register after the device is linked globally.

Device tree properties (`input_touch_parse`)

Read from the rt_input_device's rt_device OFW node via rt_dm_dev_prop_*:

Property	Effect
`touchscreen-min-x`, `touchscreen-size-x`, `touchscreen-fuzz-x`	Override `ABS_X` or `ABS_MT_POSITION_X` absinfo
`touchscreen-min-y`, `touchscreen-size-y`, `touchscreen-fuzz-y`	Y axis
`touchscreen-max-pressure`, `touchscreen-fuzz-pressure`	Pressure axis
`touchscreen-inverted-x`, `touchscreen-inverted-y`	Flip coordinates in `rt_input_parse_touch_position`
`touchscreen-swapped-x-y`	Swap X/Y absinfo and coordinates

Missing properties fall back to values already set by rt_input_set_absinfo in the panel driver.

Handler translation (`input_touch_cb`)

When touch_dev->enabled:

Input event	Touch side
`ABS_MT_SLOT`	Select active slot index
`ABS_MT_TRACKING_ID == -1`	`RT_TOUCH_EVENT_UP`, `rt_hw_touch_isr`
`ABS_MT_TRACKING_ID` valid	DOWN / MOVE, increment `down` count
`ABS_MT_POSITION_X/Y` or `ABS_X/Y`	Scale raw value to `range_x`/`range_y` using absinfo min/max
`EV_SYN` + `SYN_REPORT`	`rt_hw_touch_isr` (frame complete)

input_touch_readpoint returns one struct rt_touch_data for the current slot (GUI pull model).

Example (driver probe sketch)

struct rt_touch_info info = {
    .type = RT_TOUCH_TYPE_CAPACITANCE,
    .vendor = RT_TOUCH_VENDOR_UNKNOWN,
    .point_num = 1,
    .range_x = 800,
    .range_y = 480,
};

rt_input_set_capability(idev, EV_ABS, ABS_X);
rt_input_set_capability(idev, EV_ABS, ABS_Y);
rt_input_set_absinfo(idev, ABS_X, 0, max_x, 0, 0);
rt_input_set_absinfo(idev, ABS_Y, 0, max_y, 0, 0);

rt_input_setup_touch(idev, 0, &info);   /* 0 slots = single touch */
rt_input_device_register(idev);

/* in IRQ / thread: */
rt_input_report_touch_position(idev, x, y, RT_FALSE);
rt_input_sync(idev);

For multitouch, pass num_slots > 0, use rt_input_report_touch_slot, tracking id helpers, then rt_input_sync per frame.

Pitfalls

Issue	Mitigation
`setup_touch` after register	`input_touch_register` won't run correctly — setup before register
`info == NULL`	Properties-only mode: no `rt_touch_device` exported (handler-only path not used for HW touch register)
Missing `rt_input_sync`	Touch ISR won't see a full frame
ABS range zero	Scaling in `input_touch_cb` divides by `maximum - minimum` — set absinfo first
Unregister order	`input_touch_unregister` from `rt_input_device_unregister` — drop touch fd users first

6.3 KiB Executable File Raw Permalink Blame History

Touch bridge (RT_INPUT_TOUCHSCREEN)

Kconfig

Architecture

Driver API (input.h)

Device tree properties (input_touch_parse)

Handler translation (input_touch_cb)