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SubjectRe: [PATCH RFC] leds: Add support for per-LED device triggers
Hi,

On Thu, Jul 02, 2020 at 04:47:11PM +0200, megous hlavni wrote:
> Some LED controllers may come with an internal HW triggering mechanism
> for the LED and an ability to switch between user control of the LED,
> or the internal control. One such example is AXP20X PMIC, that allows
> wither for user control of the LED, or for internal control based on
> the state of the battery charger.
>
> Add support for registering per-LED device trigger.
>
> Names of private triggers need to be globally unique, but may clash
> with other private triggers. This is enforced during trigger
> registration. Developers can register private triggers just like
> the normal triggers, by setting private_led to a classdev
> of the LED the trigger is associated with.

I've prepared this patch based on the note here:

https://www.kernel.org/doc/html/latest/leds/leds-class.html

Future Development:

At the moment, a trigger can’t be created specifically for a single LED. There
are a number of cases where a trigger might only be mappable to a particular
LED (ACPI?). The addition of triggers provided by the LED driver should cover
this option and be possible to add without breaking the current interface.

Does it look good?

I plan to use this interface in the axp20x driver I've sent previously,
if this patch is acceptable.

thank you and regards,
o.

> Signed-off-by: Ondrej Jirman <megous@megous.com>
> ---
> drivers/leds/led-triggers.c | 12 +++++++++---
> include/linux/leds.h | 3 +++
> 2 files changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> index 79e30d2cb7a5..3011e2658404 100644
> --- a/drivers/leds/led-triggers.c
> +++ b/drivers/leds/led-triggers.c
> @@ -50,7 +50,8 @@ ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,
>
> down_read(&triggers_list_lock);
> list_for_each_entry(trig, &trigger_list, next_trig) {
> - if (sysfs_streq(buf, trig->name)) {
> + if (sysfs_streq(buf, trig->name) &&
> + (!trig->private_led || trig->private_led == led_cdev)) {
> down_write(&led_cdev->trigger_lock);
> led_trigger_set(led_cdev, trig);
> up_write(&led_cdev->trigger_lock);
> @@ -96,6 +97,9 @@ static int led_trigger_format(char *buf, size_t size,
> bool hit = led_cdev->trigger &&
> !strcmp(led_cdev->trigger->name, trig->name);
>
> + if (trig->private_led && trig->private_led != led_cdev)
> + continue;
> +
> len += led_trigger_snprintf(buf + len, size - len,
> " %s%s%s", hit ? "[" : "",
> trig->name, hit ? "]" : "");
> @@ -243,7 +247,8 @@ void led_trigger_set_default(struct led_classdev *led_cdev)
> down_read(&triggers_list_lock);
> down_write(&led_cdev->trigger_lock);
> list_for_each_entry(trig, &trigger_list, next_trig) {
> - if (!strcmp(led_cdev->default_trigger, trig->name)) {
> + if (!strcmp(led_cdev->default_trigger, trig->name) &&
> + (!trig->private_led || trig->private_led == led_cdev)) {
> led_cdev->flags |= LED_INIT_DEFAULT_TRIGGER;
> led_trigger_set(led_cdev, trig);
> break;
> @@ -280,7 +285,8 @@ int led_trigger_register(struct led_trigger *trig)
> down_write(&triggers_list_lock);
> /* Make sure the trigger's name isn't already in use */
> list_for_each_entry(_trig, &trigger_list, next_trig) {
> - if (!strcmp(_trig->name, trig->name)) {
> + if (!strcmp(_trig->name, trig->name) &&
> + (!_trig->private_led || _trig->private_led == trig->private_led)) {
> up_write(&triggers_list_lock);
> return -EEXIST;
> }
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 2451962d1ec5..0d7577c752ad 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -345,6 +345,9 @@ struct led_trigger {
> int (*activate)(struct led_classdev *led_cdev);
> void (*deactivate)(struct led_classdev *led_cdev);
>
> + /* LED-private triggers have the LED device set here. */
> + struct led_classdev *private_led;

I'm not sure what the best descriptive name is here. ^

regards,
o.

> /* LEDs under control by this trigger (for simple triggers) */
> rwlock_t leddev_list_lock;
> struct list_head led_cdevs;
> --
> 2.27.0
>

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