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leds: Introduce ordered workqueue for LEDs events instead of system_wq

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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: Alexey Romanov <avromanov@salutedevices.com>
Signed-off-by: Dmitry 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: Lee Jones <lee@kernel.org>
This commit is contained in:
Dmitry Rokosov 2024-09-04 01:39:30 +03:00 committed by Lee Jones
parent 64dd44a658
commit 32360bf6a5
3 changed files with 15 additions and 4 deletions
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12
drivers/leds/led-class.c
View File

@ -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);

6
drivers/leds/led-core.c
View File

@ -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);

1
include/linux/leds.h
View File

@ -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;