Re: [PATCH] cleanup LED documentation and make it match reality

Jacek Anaszewski
2016-10-03T09:28:09Z

Hi Pavel,

Thanks for the patch.

On 10/03/2016 10:10 AM, Pavel Machek wrote:
>
> sysfs-class-led fails to mention some important details. Also fix led
> vs LED and english.
>
> Signed-off-by: Pavel Machek <pavel@ucw.cz>
>
> --- a/Documentation/ABI/testing/sysfs-class-led
> +++ b/Documentation/ABI/testing/sysfs-class-led
> @@ -4,16 +4,25 @@ KernelVersion: 2.6.17
> Contact: Richard Purdie <rpurdie@rpsys.net>
> Description:
> Set the brightness of the LED. Most LEDs don't
> - have hardware brightness support so will just be turned on for
> + have hardware brightness support, so will just be turned on for
> non-zero brightness settings. The value is between 0 and
> /sys/class/leds/<led>/max_brightness.
>
> + 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.

This is true only in case of timer trigger, as it uses blink_brightness
property from struct led_classdev to cache current brightness, when the
the LED is in the off cycle. This is part of software blink fallback
functionality.

In case of heartbeat trigger max_brightness is always used for top level
brightness. We'd need to refactor the trigger a bit to allow for
different top brightness levels.

> +
> +
> What: /sys/class/leds/<led>/max_brightness
> Date: March 2006
> KernelVersion: 2.6.17
> Contact: Richard Purdie <rpurdie@rpsys.net>
> Description:
> - Maximum brightness level for this led, default is 255 (LED_FULL).
> + Maximum brightness level for this LED, default is 255 (LED_FULL).
> +
> + If the LED does not support different brightness levels, this
> + should be 1.
>
> What: /sys/class/leds/<led>/trigger
> Date: March 2006
> @@ -21,7 +30,7 @@ KernelVersion: 2.6.17
> Contact: Richard Purdie <rpurdie@rpsys.net>
> Description:
> Set the trigger for this LED. A trigger is a kernel based source
> - of led events.
> + of LED events.
> You can change triggers in a similar manner to the way an IO
> scheduler is chosen. Trigger specific parameters can appear in
> /sys/class/leds/<led> once a given trigger is selected.