Can I set an input callback at run time? (INPUT_CALLBACK_DEFINE(touch_dev, touch_event_callback, NULL)

[KurtE]

Suppose I wish to setup the callback function for an input object at runtime, how do I do it?

In this case, suppose the board (shield) has a PT911 touch controller on it, and I would like to have my own input controller handling
the inputs.

If I look at the example:
https://github.com/zephyrproject-rtos/zephyr/blob/main/samples/subsys/input/draw_touch_events/src/main.c

Has a callback defined:

static struct {
	size_t x;
	size_t y;
	bool pressed;
} touch_point, touch_point_drawn;

static void touch_event_callback(struct input_event *evt, void *user_data)
{
	if (evt->code == INPUT_ABS_X) {
		touch_point.x = evt->value;
	}
	if (evt->code == INPUT_ABS_Y) {
		touch_point.y = evt->value;
	}
	if (evt->code == INPUT_BTN_TOUCH) {
		touch_point.pressed = evt->value;
	}
	if (evt->sync) {
		k_sem_give(&sync);
	}
}
INPUT_CALLBACK_DEFINE(touch_dev, touch_event_callback, NULL);

Which is fine, in many cases, but suppose I wish to load this code using LLEXT. The INPUT_CALLBACK_DEFINE does not
setup the callback function.

Is there some runtime API that can dynamically set this up?

In our searching, we found something that looked like it might work using kscan:
#60668

It sets up a callback like:

        kscan_config(gt911_dev, gt911_cb);
	kscan_enable_callback(gt911_dev);

but it appears like kscan has been phased out. I am not seeing any examples of it anymore and if I add the lines:

CONFIG_KSCAN=y
CONFIG_KSCAN_GT911=y

to conf, the build fails.

Is there some other mechanism? maybe something like the GPIO ones? Ones like:
gpio_init_callback and gpio_add_callback

Thanks,
Kurt

[kartben]

@fabiobaltieri might be able to chime in

[fabiobaltieri]

Can't be done at the moment, but it'd be very easy to a static callback that goes through a dynamic list. Or just implement the whole thing in the subsystem and make it Kconfig optional, don't see a reason not to accept such a contribution.

[KurtE]

Thanks!