Commit 32360bf6 authored by Dmitry Rokosov's avatar Dmitry Rokosov Committed by Lee Jones
Browse files

leds: Introduce ordered workqueue for LEDs events instead of system_wq 



This allows to setup ordered workqueue for LEDs events. This may be
useful, because default 'system_wq' does not guarantee execution order
of each work_struct, thus for several brightness update requests (for
multiple LEDs), real brightness switch could be in random order.

Yes, for sysfs-based LEDs we have flush_work() call inside
brightness_store() operation, but it's blocking call, so userspace
caller can be blocked at a long time, which means LEDs animation stream
can be broken.

Ordered workqueue has the same behaviour as system_wq + flush_work(),
but all scheduled works are async and userspace caller is not blocked,
which it better for userspace animation scheduling.

Signed-off-by: default avatarAlexey Romanov <avromanov@salutedevices.com>
Signed-off-by: default avatarDmitry Rokosov <ddrokosov@salutedevices.com>
Link: https://lore.kernel.org/r/20240903223936.21292-1-ddrokosov@salutedevices.com


[Lee: Couple of style fix-ups]
Signed-off-by: default avatarLee Jones <lee@kernel.org>
parent 64dd44a6

drivers/leds/led-class.c

+11 −1
Original line number Diff line number Diff line
@@ -25,6 +25,8 @@ 
static DEFINE_MUTEX(leds_lookup_lock);

static LIST_HEAD(leds_lookup_list);



static struct workqueue_struct *leds_wq;



static ssize_t brightness_show(struct device *dev,

		struct device_attribute *attr, char *buf)

{
@@ -57,7 +59,6 @@ static ssize_t brightness_store(struct device *dev, 
	if (state == LED_OFF)

		led_trigger_remove(led_cdev);

	led_set_brightness(led_cdev, state);

	flush_work(&led_cdev->set_brightness_work);



	ret = size;

unlock:
@@ -549,6 +550,8 @@ int led_classdev_register_ext(struct device *parent, 


	led_update_brightness(led_cdev);



	led_cdev->wq = leds_wq;



	led_init_core(led_cdev);



#ifdef CONFIG_LEDS_TRIGGERS
@@ -667,12 +670,19 @@ EXPORT_SYMBOL_GPL(devm_led_classdev_unregister); 


static int __init leds_init(void)

{

	leds_wq = alloc_ordered_workqueue("leds", 0);

	if (!leds_wq) {

		pr_err("Failed to create LEDs ordered workqueue\n");

		return -ENOMEM;

	}



	return class_register(&leds_class);

}



static void __exit leds_exit(void)

{

	class_unregister(&leds_class);

	destroy_workqueue(leds_wq);

}



subsys_initcall(leds_init);

drivers/leds/led-core.c

+3 −3
Original line number Diff line number Diff line
@@ -273,7 +273,7 @@ void led_blink_set_nosleep(struct led_classdev *led_cdev, unsigned long delay_on 
		led_cdev->delayed_delay_on = delay_on;

		led_cdev->delayed_delay_off = delay_off;

		set_bit(LED_SET_BLINK, &led_cdev->work_flags);

		schedule_work(&led_cdev->set_brightness_work);

		queue_work(led_cdev->wq, &led_cdev->set_brightness_work);

		return;

	}
@@ -304,7 +304,7 @@ void led_set_brightness(struct led_classdev *led_cdev, unsigned int brightness) 
		 */

		if (!brightness) {

			set_bit(LED_BLINK_DISABLE, &led_cdev->work_flags);

			schedule_work(&led_cdev->set_brightness_work);

			queue_work(led_cdev->wq, &led_cdev->set_brightness_work);

		} else {

			set_bit(LED_BLINK_BRIGHTNESS_CHANGE,

				&led_cdev->work_flags);
@@ -340,7 +340,7 @@ void led_set_brightness_nopm(struct led_classdev *led_cdev, unsigned int value) 
		set_bit(LED_SET_BRIGHTNESS_OFF, &led_cdev->work_flags);

	}



	schedule_work(&led_cdev->set_brightness_work);

	queue_work(led_cdev->wq, &led_cdev->set_brightness_work);

}

EXPORT_SYMBOL_GPL(led_set_brightness_nopm);

include/linux/leds.h

+1 −0
Original line number Diff line number Diff line
@@ -171,6 +171,7 @@ struct led_classdev { 
	int			 new_blink_brightness;

	void			(*flash_resume)(struct led_classdev *led_cdev);



	struct workqueue_struct *wq;			/* LED workqueue */

	struct work_struct	set_brightness_work;

	int			delayed_set_value;

	unsigned long		delayed_delay_on;