[1/1] leds: trigger: Add new LED Input events trigger

Add a new trigger which turns LEDs on when there is input
(/dev/input/event*) activity and turns them back off again after there has
been no activity for 5 seconds.

This is primarily intended to control LED devices which are a backlight for
capacitive touch-buttons, such as e.g. the menu / home / back buttons found
on the bottom bezel of many somewhat older smartphones and tablets.

This can also be used to turn on the keyboard backlight LED on input
events and turn the keyboard backlight off again when idle.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/leds/trigger/Kconfig                |  16 ++
 drivers/leds/trigger/Makefile               |   1 +
 drivers/leds/trigger/ledtrig-input-events.c | 252 ++++++++++++++++++++
 3 files changed, 269 insertions(+)
 create mode 100644 drivers/leds/trigger/ledtrig-input-events.c

Hi All,

On 5/5/24 2:32 PM, Hans de Goede wrote:
> Add a new trigger which turns LEDs on when there is input
> (/dev/input/event*) activity and turns them back off again after there has
> been no activity for 5 seconds.
> 
> This is primarily intended to control LED devices which are a backlight for
> capacitive touch-buttons, such as e.g. the menu / home / back buttons found
> on the bottom bezel of many somewhat older smartphones and tablets.
> 
> This can also be used to turn on the keyboard backlight LED on input
> events and turn the keyboard backlight off again when idle.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Self-nack for this patch. I still believe the basic idea of having such
a trigger is good. But the way how this implementation uses
the trigger->led_cdevs list is racy and that list is better left as
a private implementation detail of drivers/leds/led-trigger.c and not
used directly by triggers.

So I'm going to rework this for v2 so that it no longer loops over
trigger->led_cdevs list.

Regards,

Hans




> ---
>  drivers/leds/trigger/Kconfig                |  16 ++
>  drivers/leds/trigger/Makefile               |   1 +
>  drivers/leds/trigger/ledtrig-input-events.c | 252 ++++++++++++++++++++
>  3 files changed, 269 insertions(+)
>  create mode 100644 drivers/leds/trigger/ledtrig-input-events.c
> 
> diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
> index d11d80176fc0..809ffba0cd6a 100644
> --- a/drivers/leds/trigger/Kconfig
> +++ b/drivers/leds/trigger/Kconfig
> @@ -152,4 +152,20 @@ config LEDS_TRIGGER_TTY
>  
>  	  When build as a module this driver will be called ledtrig-tty.
>  
> +config LEDS_TRIGGER_INPUT_EVENTS
> +	tristate "LED Input events trigger"
> +	depends on INPUT
> +	help
> +	  Turn LEDs on when there is input (/dev/input/event*) activity and turn
> +	  them back off again after there has been no activity for 5 seconds.
> +
> +	  This is primarily intended to control LEDs which are a backlight for
> +	  capacitive touch-buttons, such as e.g. the menu / home / back buttons
> +	  found on the bottom bezel of many older smartphones and tablets.
> +
> +	  This can also be used to turn on the keyboard backlight LED on
> +	  input events and turn the keyboard backlight off again when idle.
> +
> +	  When build as a module this driver will be called ledtrig-input-events.
> +
>  endif # LEDS_TRIGGERS
> diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
> index 25c4db97cdd4..f78a3077efc7 100644
> --- a/drivers/leds/trigger/Makefile
> +++ b/drivers/leds/trigger/Makefile
> @@ -16,3 +16,4 @@ obj-$(CONFIG_LEDS_TRIGGER_NETDEV)	+= ledtrig-netdev.o
>  obj-$(CONFIG_LEDS_TRIGGER_PATTERN)	+= ledtrig-pattern.o
>  obj-$(CONFIG_LEDS_TRIGGER_AUDIO)	+= ledtrig-audio.o
>  obj-$(CONFIG_LEDS_TRIGGER_TTY)		+= ledtrig-tty.o
> +obj-$(CONFIG_LEDS_TRIGGER_INPUT_EVENTS)	+= ledtrig-input-events.o
> diff --git a/drivers/leds/trigger/ledtrig-input-events.c b/drivers/leds/trigger/ledtrig-input-events.c
> new file mode 100644
> index 000000000000..cb86d1afeab4
> --- /dev/null
> +++ b/drivers/leds/trigger/ledtrig-input-events.c
> @@ -0,0 +1,252 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Input Events LED trigger
> + *
> + * Copyright (C) 2024 Hans de Goede <hansg@kernel.org>
> + * Partially based on Atsushi Nemoto's ledtrig-heartbeat.c.
> + */
> +
> +#include <linux/input.h>
> +#include <linux/jiffies.h>
> +#include <linux/leds.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +#include <linux/workqueue.h>
> +#include "../leds.h"
> +
> +#define DEFAULT_LED_OFF_DELAY_MS			5000
> +
> +struct input_events_data {
> +	struct delayed_work work;
> +	spinlock_t lock;
> +	struct led_classdev *led_cdev;
> +	int led_cdev_saved_flags;
> +	/* To avoid repeatedly setting the brightness while there is events */
> +	bool led_on;
> +	unsigned long led_off_time;
> +	unsigned long led_off_delay;
> +};
> +
> +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_set_brightness_nosleep(data->led_cdev, LED_OFF);
> +		data->led_on = false;
> +	}
> +
> +	spin_unlock_irq(&data->lock);
> +}
> +
> +static ssize_t delay_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct input_events_data *input_events_data = led_trigger_get_drvdata(dev);
> +
> +	return sysfs_emit(buf, "%lu\n", input_events_data->led_off_delay);
> +}
> +
> +static ssize_t delay_store(struct device *dev, struct device_attribute *attr,
> +			   const char *buf, size_t size)
> +{
> +	struct input_events_data *input_events_data = led_trigger_get_drvdata(dev);
> +	unsigned long delay;
> +	int ret;
> +
> +	ret = kstrtoul(buf, 0, &delay);
> +	if (ret)
> +		return ret;
> +
> +	/* Clamp between 0.5 and 1000 seconds */
> +	delay = clamp_val(delay, 500UL, 1000000UL);
> +	input_events_data->led_off_delay = msecs_to_jiffies(delay);
> +
> +	return size;
> +}
> +
> +static DEVICE_ATTR_RW(delay);
> +
> +static struct attribute *input_events_led_attrs[] = {
> +	&dev_attr_delay.attr,
> +	NULL
> +};
> +ATTRIBUTE_GROUPS(input_events_led);
> +
> +static int input_events_activate(struct led_classdev *led_cdev)
> +{
> +	struct input_events_data *data;
> +
> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	INIT_DELAYED_WORK(&data->work, led_input_events_work);
> +	spin_lock_init(&data->lock);
> +	data->led_cdev = led_cdev;
> +	data->led_cdev_saved_flags = led_cdev->flags;
> +	data->led_off_delay = msecs_to_jiffies(DEFAULT_LED_OFF_DELAY_MS);
> +
> +	led_set_trigger_data(led_cdev, data);
> +
> +	/*
> +	 * Use led_cdev->blink_brightness + LED_BLINK_SW flag so that sysfs
> +	 * brightness writes will change led_cdev->new_blink_brightness for
> +	 * configuring the on state brightness (like ledtrig-heartbeat).
> +	 */
> +	if (!led_cdev->blink_brightness)
> +		led_cdev->blink_brightness = led_cdev->max_brightness;
> +
> +	set_bit(LED_BLINK_SW, &led_cdev->work_flags);
> +	/* Turn LED off during suspend, original flags are restored on deactivate() */
> +	led_cdev->flags |= LED_CORE_SUSPENDRESUME;
> +
> +	/* Start with LED off */
> +	led_set_brightness_nosleep(data->led_cdev, LED_OFF);
> +	return 0;
> +}
> +
> +static void input_events_deactivate(struct led_classdev *led_cdev)
> +{
> +	struct input_events_data *data = led_get_trigger_data(led_cdev);
> +
> +	led_cdev->flags = data->led_cdev_saved_flags;
> +	clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
> +	cancel_delayed_work_sync(&data->work);
> +	kfree(data);
> +}
> +
> +static struct led_trigger input_events_led_trigger = {
> +	.name       = "input-events",
> +	.activate   = input_events_activate,
> +	.deactivate = input_events_deactivate,
> +	.groups     = input_events_led_groups,
> +};
> +
> +static void input_events_event(struct input_handle *handle, unsigned int type,
> +			       unsigned int code, int data)
> +{
> +	struct led_classdev *led_cdev;
> +
> +	rcu_read_lock();
> +	list_for_each_entry_rcu(led_cdev, &input_events_led_trigger.led_cdevs, trig_list) {
> +		struct input_events_data *data = led_get_trigger_data(led_cdev);
> +		unsigned long led_off_delay = READ_ONCE(data->led_off_delay);
> +		unsigned long flags;
> +
> +		if (test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE, &led_cdev->work_flags))
> +			led_cdev->blink_brightness = led_cdev->new_blink_brightness;
> +
> +		spin_lock_irqsave(&data->lock, flags);
> +
> +		if (!data->led_on) {
> +			led_set_brightness_nosleep(led_cdev, led_cdev->blink_brightness);
> +			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);
> +	}
> +	rcu_read_unlock();
> +}
> +
> +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(struct input_handle), GFP_KERNEL);
> +	if (!handle)
> +		return -ENOMEM;
> +
> +	handle->dev = dev;
> +	handle->handler = handler;
> +	handle->name = "input-events";
> +
> +	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 =	"input-events",
> +	.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;
> +
> +	ret = led_trigger_register(&input_events_led_trigger);
> +	if (ret)
> +		return ret;
> +
> +	ret = input_register_handler(&input_events_handler);
> +	if (ret) {
> +		led_trigger_unregister(&input_events_led_trigger);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static void __exit input_events_exit(void)
> +{
> +	input_unregister_handler(&input_events_handler);
> +	led_trigger_unregister(&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");