Re: [PATCH] leds: Allow drivers to update the core, and generate events on changes

From: Jacek Anaszewski
Date: Tue Dec 27 2016 - 17:58:42 EST

Hi Gabriele, Pavel,

On 12/27/2016 09:07 PM, Pavel Machek wrote:
> Hi!
>> Similarily to commit 325253a6b2de ("backlight: Allow drivers to update
>> the core, and generate events on changes"), inform userspace about
>> brightness changes and allow drivers to request updates of the
>> brightness value.
> First... we had similar patch in tree, and it caused problems, we are
> now trying to figure out how to do it properly.
> LED can be updated many times per second, uevent is probably _not_
> good mechanism to achieve that.
> Generating uevent for /sys changes does not make much sense, right?
>> +extern void led_brightness_force_update(struct led_classdev *led_cdev,
>> + enum led_brightness_update_reason reason);
> I see this may make some sense, but there are no uses for this in this
> patch.
> My preffered solution would be ... for hardware that changes led
> brightness itself, introduce a "trigger", so that userspace knows this
> led is special, and then provide poll()able /sys fs file interested
> parties can read.

I've recently submitted for a discussion the idea of "persistent
triggers" [0]. Any feedback is very much appreciated.


Best regards,
Jacek Anaszewski