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

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Message-ID: <20161227210245.GA7952@amd>
Date:   Tue, 27 Dec 2016 22:02:45 +0100
From:   Pavel Machek <pavel@....cz>
To:     Gabriele Mazzotta <gabriele.mzt@...il.com>
Cc:     rpurdie@...ys.net, jacek.anaszewski@...il.com,
        linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] leds: Allow drivers to update the core, and generate
 events on changes

Hi!

> > Generating uevent for /sys changes does not make much sense, right?
> 
> I planned to use this patch mostly for keyboard backlights, for
> which some DEs provide a UI similar to the one for screen backlights.
> Having uevents also for /sys changes means having the UI always in
> sync with the kernel/hardware, as it happens for screen backlights.
> In case of LEDs only the application changing the brightness is
> aware of the change.
> 
> >> +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.
> 
> OK, I'll see if I can come up something good.

Please see this thread:

Date: Tue, 15 Nov 2016 13:06:14 +0100
From: Hans de Goede <hdegoede@...hat.com>
To: Pavel Machek <pavel@....cz>
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>, Hans de Goede <hdegoede@...hat.com>
Subject: Re: LEDs that change brightness "itself" -- that's a
trigger. Re: PM regression with LED changes in next-20161109


...and you may want to cc: Hans de Goede <hdegoede@...hat.com> . He is
apparently solving same problem.

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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