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leds: class: Remove hardware control trigger when writing brightness

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Since commit b819dc7d8f ("leds: core: Report ENODATA for brightness of
hardware controlled LED"), the brightness attribute becomes write-only
when the LED is controlled fully by the hardware. A write-only attribute
is very confusing.

Moreover, most LED drivers set hardware brightness innocently with the
side effect of disabling hardware control, but the hardware control
trigger remains active, resulting in the software and hardware being out
of sync.

Fix it by removing the hardware control trigger when writing the
brightness attribute.

This should also match the semantics of hardware control:

    When the LED is in hw control, no software blink is possible and
    doing so will effectively disable hw control.

Fixes: b819dc7d8f ("leds: core: Report ENODATA for brightness of hardware controlled LED")
Acked-by: Ike Panhc <ikepanhc@gmail.com>
Signed-off-by: Rong Zhang <i@rong.moe>
Link: https://patch.msgid.link/20260921-leds-trigger-hw-changed-v7-3-fe3cdb6dec51@rong.moe
Signed-off-by: Lee Jones <lee@kernel.org>
This commit is contained in:
Rong Zhang 2026-09-21 03:40:17 +08:00 committed by Lee Jones
parent 7879d62774
commit 96b4ddd6d2
4 changed files with 17 additions and 1 deletions
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4
Documentation/ABI/testing/sysfs-class-led
View File

@ -28,7 +28,9 @@ Description:
Writing 0 to this file clears active trigger.
Writing non-zero to this file while trigger is active changes the
top brightness trigger is going to use.
top brightness trigger is going to use, unless the current
trigger is offloaded to hardware (in which case writing any
value will deactivate the trigger).

3
drivers/leds/led-class.c
View File

@ -64,6 +64,9 @@ static ssize_t brightness_store(struct device *dev,
if (state == LED_OFF)
led_trigger_remove(led_cdev);
else
led_trigger_remove_hw_control(led_cdev);
led_set_brightness(led_cdev, state);
ret = size;

9
drivers/leds/led-triggers.c
View File

@ -287,6 +287,15 @@ void led_trigger_remove(struct led_classdev *led_cdev)
}
EXPORT_SYMBOL_GPL(led_trigger_remove);
void led_trigger_remove_hw_control(struct led_classdev *led_cdev)
{
guard(rwsem_write)(&led_cdev->trigger_lock);
if (__led_trigger_is_hw_controlled(led_cdev))
led_trigger_set(led_cdev, NULL);
}
EXPORT_SYMBOL_GPL(led_trigger_remove_hw_control);
static bool led_match_default_trigger(struct led_classdev *led_cdev,
struct led_trigger *trig)
{

2
include/linux/leds.h
View File

@ -533,6 +533,7 @@ void led_trigger_blink_oneshot(struct led_trigger *trigger,
void led_trigger_set_default(struct led_classdev *led_cdev);
int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trigger);
void led_trigger_remove(struct led_classdev *led_cdev);
void led_trigger_remove_hw_control(struct led_classdev *led_cdev);
bool led_trigger_is_hw_controlled(struct led_classdev *led_cdev);
@ -586,6 +587,7 @@ static inline int led_trigger_set(struct led_classdev *led_cdev,
}
static inline void led_trigger_remove(struct led_classdev *led_cdev) {}
static inline void led_trigger_remove_hw_control(struct led_classdev *led_cdev) {}
static inline bool led_trigger_is_hw_controlled(struct led_classdev *led_cdev)
{