drivers/leds/trigger/ledtrig-input-events.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Input Events LED trigger
 *
 * Copyright (C) 2024 Hans de Goede <hansg@kernel.org>
 */

#include <linux/input.h>
#include <linux/jiffies.h>
#include <linux/leds.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>
#include "../leds.h"

static unsigned long led_off_delay_ms = 5000;
module_param(led_off_delay_ms, ulong, 0644);
MODULE_PARM_DESC(led_off_delay_ms,
	"Specify delay in ms for turning LEDs off after last input event");

static struct input_events_data {
	struct delayed_work work;
	spinlock_t lock;
	/* To avoid repeatedly setting the brightness while there are events */
	bool led_on;
	unsigned long led_off_time;
} input_events_data;

static struct led_trigger *input_events_led_trigger;

static void led_input_events_work(struct work_struct *work)
{
	struct input_events_data *data =
		container_of(work, struct input_events_data, work.work);

	spin_lock_irq(&data->lock);

	/*
	 * This time_after_eq() check avoids a race where this work starts
	 * running before a new event pushed led_off_time back.
	 */
	if (time_after_eq(jiffies, data->led_off_time)) {
		led_trigger_event(input_events_led_trigger, LED_OFF);
		data->led_on = false;
	}

	spin_unlock_irq(&data->lock);
}

static void input_events_event(struct input_handle *handle, unsigned int type,
			       unsigned int code, int val)
{
	struct input_events_data *data = &input_events_data;
	unsigned long led_off_delay = msecs_to_jiffies(led_off_delay_ms);
	unsigned long flags;

	spin_lock_irqsave(&data->lock, flags);

	if (!data->led_on) {
		led_trigger_event(input_events_led_trigger, LED_FULL);
		data->led_on = true;
	}
	data->led_off_time = jiffies + led_off_delay;

	spin_unlock_irqrestore(&data->lock, flags);

	mod_delayed_work(system_wq, &data->work, led_off_delay);
}

static int input_events_connect(struct input_handler *handler, struct input_dev *dev,
				const struct input_device_id *id)
{
	struct input_handle *handle;
	int ret;

	handle = kzalloc(sizeof(*handle), GFP_KERNEL);
	if (!handle)
		return -ENOMEM;

	handle->dev = dev;
	handle->handler = handler;
	handle->name = KBUILD_MODNAME;

	ret = input_register_handle(handle);
	if (ret)
		goto err_free_handle;

	ret = input_open_device(handle);
	if (ret)
		goto err_unregister_handle;

	return 0;

err_unregister_handle:
	input_unregister_handle(handle);
err_free_handle:
	kfree(handle);
	return ret;
}

static void input_events_disconnect(struct input_handle *handle)
{
	input_close_device(handle);
	input_unregister_handle(handle);
	kfree(handle);
}

static const struct input_device_id input_events_ids[] = {
	{
		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
		.evbit = { BIT_MASK(EV_KEY) },
	},
	{
		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
		.evbit = { BIT_MASK(EV_REL) },
	},
	{
		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
		.evbit = { BIT_MASK(EV_ABS) },
	},
	{ }
};

static struct input_handler input_events_handler = {
	.name = KBUILD_MODNAME,
	.event = input_events_event,
	.connect = input_events_connect,
	.disconnect = input_events_disconnect,
	.id_table = input_events_ids,
};

static int __init input_events_init(void)
{
	int ret;

	INIT_DELAYED_WORK(&input_events_data.work, led_input_events_work);
	spin_lock_init(&input_events_data.lock);

	led_trigger_register_simple("input-events", &input_events_led_trigger);

	ret = input_register_handler(&input_events_handler);
	if (ret) {
		led_trigger_unregister_simple(input_events_led_trigger);
		return ret;
	}

	return 0;
}

static void __exit input_events_exit(void)
{
	input_unregister_handler(&input_events_handler);
	cancel_delayed_work_sync(&input_events_data.work);
	led_trigger_unregister_simple(input_events_led_trigger);
}

module_init(input_events_init);
module_exit(input_events_exit);

MODULE_AUTHOR("Hans de Goede <hansg@kernel.org>");
MODULE_DESCRIPTION("Input Events LED trigger");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ledtrig:input-events");