linux-kernel - LEDs that change brightness "itself" -- that's a trigger. Re: PM regression with LED changes in next-20161109

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Date:   Tue, 15 Nov 2016 11:31:33 +0100
From:   Pavel Machek <pavel@....cz>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Jacek Anaszewski <j.anaszewski@...sung.com>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Tony Lindgren <tony@...mide.com>, linux-leds@...r.kernel.org,
        linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Darren Hart <dvhart@...radead.org>
Subject: LEDs that change brightness "itself" -- that's a trigger. Re: PM
 regression with LED changes in next-20161109

Hi!

> >Hmm, v4 still calls led_notify_brightness_change(led_cdev)
> >from both __led_set_brightness() and __led_set_brightness_blocking().
> 
> Ugh, I see I accidentally send a v4 twice, instead of
> calling the version which dropped those called v5 as
> I should have, sorry.
> 
> The v4 which I would like to see merged, the one with
> those calls dropped, is here:
> 
> https://patchwork.kernel.org/patch/9423093/

Please, lets fix this properly.

The LED you are talking about _has_ a trigger, implemented in
hardware. That trigger can change LED brightness behind kernel's (and
userspace's) back. Don't pretend the trigger does not exist, it does.

And when you do that, you'll have nice place to report changes to
userspace -- trigger can now export that information, and offer poll()
interface.

Thanks,
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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