linux-kernel - Re: LED devices & poll() for brightness attribute

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Message-ID: <20170222122557.GA3807@amd>
Date:   Wed, 22 Feb 2017 13:25:57 +0100
From:   Pavel Machek <pavel@....cz>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     Richard Purdie <rpurdie@...ys.net>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
        Darren Hart <dvhart@...radead.org>,
        platform-driver-x86@...r.kernel.org
Subject: Re: LED devices & poll() for brightness attribute

Hi!

> But this support is useful just for one single central userspace
> application which will control all leds in system other application
> which will change state by /sys/class/leds/ will de-synchronize that one
> central application.

Yes. Does it matter for some real use case?

> So I think new ABI is not sufficient and I would propose to add poll()
> support also for changes done by userspace, write() to attribute
> /sys/class/leds/.../brightness.

Not easily possible, as we have triggers, and this was discussed in
great great lengths before. Please go through that discussion.
								Pavel
									
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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