* [PATCH v4 1/2] leds: triggers: Add led_trigger_for_each_led()
2026-10-30 13:51 [PATCH v4 0/2] leds: trigger: input-events: Restore previous brightness on input Nikolay Plastinin via B4 Relay
@ 2026-10-30 13:51 ` Nikolay Plastinin via B4 Relay
2026-10-30 13:51 ` [PATCH v4 2/2] leds: trigger: input-events: Restore previous brightness on input Nikolay Plastinin via B4 Relay
1 sibling, 0 replies; 3+ messages in thread
From: Nikolay Plastinin via B4 Relay @ 2026-10-30 13:51 UTC (permalink / raw)
To: Lee Jones, Pavel Machek
Cc: Hans de Goede, linux-leds, linux-kernel, Nikolay Plastinin
From: Nikolay Plastinin <plaztininikolai@gmail.com>
led_trigger_event() sets one brightness for all LEDs using a trigger.
A trigger which restores a different brightness per LED needs to iterate
over the attached LEDs instead.
Add led_trigger_for_each_led(), a wrapper around list_for_each_entry_rcu(),
so triggers can perform this iteration without spelling out the list
members. Document that callers must hold the RCU read lock throughout
the iteration and must not sleep while accessing the LEDs.
Assisted-by: LLM
Signed-off-by: Nikolay Plastinin <plaztininikolai@gmail.com>
---
include/linux/leds.h | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/include/linux/leds.h b/include/linux/leds.h
index a515f075c..675c58661 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -11,6 +11,7 @@
#include <dt-bindings/leds/common.h>
#include <linux/device.h>
#include <linux/mutex.h>
+#include <linux/rculist.h>
#include <linux/rwsem.h>
#include <linux/spinlock.h>
#include <linux/timer.h>
@@ -502,6 +503,17 @@ struct led_trigger {
const struct attribute_group **groups;
};
+/**
+ * led_trigger_for_each_led - iterate over the LEDs attached to a trigger
+ * @pos: struct led_classdev pointer used as the loop cursor
+ * @trig: trigger whose LEDs are iterated
+ *
+ * The caller must hold the RCU read lock throughout the iteration and must
+ * not sleep while accessing the LEDs.
+ */
+#define led_trigger_for_each_led(pos, trig) \
+ list_for_each_entry_rcu(pos, &(trig)->led_cdevs, trig_list)
+
/*
* Currently the attributes in struct led_trigger::groups are added directly to
* the LED device. As this might change in the future, the following
--
2.56.0
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH v4 2/2] leds: trigger: input-events: Restore previous brightness on input
2026-10-30 13:51 [PATCH v4 0/2] leds: trigger: input-events: Restore previous brightness on input Nikolay Plastinin via B4 Relay
2026-10-30 13:51 ` [PATCH v4 1/2] leds: triggers: Add led_trigger_for_each_led() Nikolay Plastinin via B4 Relay
@ 2026-10-30 13:51 ` Nikolay Plastinin via B4 Relay
1 sibling, 0 replies; 3+ messages in thread
From: Nikolay Plastinin via B4 Relay @ 2026-10-30 13:51 UTC (permalink / raw)
To: Lee Jones, Pavel Machek
Cc: Hans de Goede, linux-leds, linux-kernel, Nikolay Plastinin
From: Nikolay Plastinin <plaztininikolai@gmail.com>
The trigger turns the LEDs back on with LED_FULL, which the LED core
clamps to max_brightness. For keyboard backlights with several levels,
such as asus::kbd_backlight, this means the backlight always comes back
at maximum after being idle instead of at the level the user picked.
Remember the brightness per LED before turning it off and restore it on
the next input event. Keep the level in a per-LED state struct allocated
in activate() and freed in deactivate(), converting the simple trigger
to a regular trigger. Pick up brightness changes made while the LED is
on before saving the level again.
Use led_trigger_for_each_led() under guard(rcu)() for both the on and
off paths. Skip LEDs whose activate() callback has not set up their
state yet.
Clear trigger_data under the same lock used by the LED walker before
freeing the per-LED state. Although normal trigger removal waits for an
RCU grace period, the device_add_groups() error path calls deactivate()
while the LED is still linked, so a walker must see NULL after teardown.
The previous revision was tested on an ASUS ROG Flow X13 GV302XV:
keyboard backlight levels 1 and 2 were restored after idle timeout and
keyboard input, and 20 trigger activate/deactivate cycles completed
successfully.
Assisted-by: LLM
Signed-off-by: Nikolay Plastinin <plaztininikolai@gmail.com>
---
drivers/leds/trigger/ledtrig-input-events.c | 76 ++++++++++++++++++++++++++---
1 file changed, 70 insertions(+), 6 deletions(-)
diff --git a/drivers/leds/trigger/ledtrig-input-events.c b/drivers/leds/trigger/ledtrig-input-events.c
index d057b2a23..6b0bfd343 100644
--- a/drivers/leds/trigger/ledtrig-input-events.c
+++ b/drivers/leds/trigger/ledtrig-input-events.c
@@ -28,7 +28,69 @@ static struct input_events_data {
unsigned long led_off_time;
} input_events_data;
-static struct led_trigger *input_events_led_trigger;
+struct input_events_led {
+ /* Brightness to restore on the next input event */
+ int brightness;
+};
+
+static int input_events_activate(struct led_classdev *led_cdev)
+{
+ struct input_events_data *data = &input_events_data;
+ struct input_events_led *led;
+ unsigned long flags;
+
+ led = kzalloc_obj(*led);
+ if (!led)
+ return -ENOMEM;
+
+ /* Start with the current brightness, or full if the LED is off */
+ led->brightness = led_cdev->brightness ?: led_cdev->max_brightness;
+
+ spin_lock_irqsave(&data->lock, flags);
+ led_set_trigger_data(led_cdev, led);
+ led_set_brightness(led_cdev, data->led_on ? led->brightness : LED_OFF);
+ spin_unlock_irqrestore(&data->lock, flags);
+
+ return 0;
+}
+
+static void input_events_deactivate(struct led_classdev *led_cdev)
+{
+ struct input_events_led *led;
+
+ scoped_guard(spinlock_irqsave, &input_events_data.lock) {
+ led = led_get_trigger_data(led_cdev);
+ led_set_trigger_data(led_cdev, NULL);
+ }
+ kfree(led);
+}
+
+static struct led_trigger input_events_led_trigger = {
+ .name = "input-events",
+ .activate = input_events_activate,
+ .deactivate = input_events_deactivate,
+};
+
+/* Must be called with input_events_data.lock held */
+static void input_events_set_leds(bool on)
+{
+ struct led_classdev *led_cdev;
+
+ guard(rcu)();
+ led_trigger_for_each_led(led_cdev, &input_events_led_trigger) {
+ struct input_events_led *led = led_get_trigger_data(led_cdev);
+
+ /* Not yet activated, or already deactivated during error unwind */
+ if (!led)
+ continue;
+
+ /* Preserve brightness changes made while the LED was on. */
+ if (led_cdev->brightness)
+ led->brightness = led_cdev->brightness;
+
+ led_set_brightness(led_cdev, on ? led->brightness : LED_OFF);
+ }
+}
static void led_input_events_work(struct work_struct *work)
{
@@ -42,7 +104,7 @@ static void led_input_events_work(struct work_struct *work)
* 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);
+ input_events_set_leds(false);
data->led_on = false;
}
@@ -59,7 +121,7 @@ static void input_events_event(struct input_handle *handle, unsigned int type,
spin_lock_irqsave(&data->lock, flags);
if (!data->led_on) {
- led_trigger_event(input_events_led_trigger, LED_FULL);
+ input_events_set_leds(true);
data->led_on = true;
}
data->led_off_time = jiffies + led_off_delay;
@@ -138,11 +200,13 @@ static int __init input_events_init(void)
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 = led_trigger_register(&input_events_led_trigger);
+ if (ret)
+ return ret;
ret = input_register_handler(&input_events_handler);
if (ret) {
- led_trigger_unregister_simple(input_events_led_trigger);
+ led_trigger_unregister(&input_events_led_trigger);
return ret;
}
@@ -153,7 +217,7 @@ 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);
+ led_trigger_unregister(&input_events_led_trigger);
}
module_init(input_events_init);
--
2.56.0
^ permalink raw reply [flat|nested] 3+ messages in thread