linux-kernel - Re: [PATCH v3] leds: Introduce userspace leds driver

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Date:   Fri, 16 Sep 2016 07:59:27 +0200
From:   Pavel Machek <pavel@....cz>
To:     David Lechner <david@...hnology.com>
Cc:     Jacek Anaszewski <j.anaszewski@...sung.com>,
        Richard Purdie <rpurdie@...ys.net>,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        Marcel Holtmann <marcel@...tmann.org>
Subject: Re: [PATCH v3] leds: Introduce userspace leds driver

Hi!

+The current brightness is found by reading a single byte from the
character
+device. Values are unsigned: 0 to 255. Reading does not block and
always returns
+the most recent brightness value. The device node can also be polled
to notify
+when the brightness value changes.

What is going on there? We have O_NONBLOCK, user should be able to
select if he wants blocking behaviour or not.

And yes, there's interface for creating a LED, but not one for
deleting it?

And... how is it going to work with multiple LEDs? Userspace gets
single bytes with brightness. How does it know to which LED the
brightness belongs?

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