linux-kernel - Re: [PATCH v5 1/4] leds: core: add generic support for RGB Color LED's

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Message-ID: <20160401125540.GC11860@amd>
Date:	Fri, 1 Apr 2016 14:55:40 +0200
From:	Pavel Machek <pavel@....cz>
To:	Heiner Kallweit <hkallweit1@...il.com>
Cc:	Jacek Anaszewski <j.anaszewski@...sung.com>, pali.rohar@...il.com,
	sre@...nel.org, khilman@...nel.org, aaro.koskinen@....fi,
	ivo.g.dimitrov.75@...il.com,
	Patrik Bachan <patrikbachan@...il.com>, serge@...lyn.com,
	Greg KH <greg@...ah.com>, linux-leds@...r.kernel.org,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v5 1/4] leds: core: add generic support for RGB Color
 LED's

Hi!

> > pavel@duo:~$ ls -1 /sys/class/leds/
> > tpacpi:green:batt
> > tpacpi:orange:batt
> >
> > This is physically 2 leds but hidden under one indicator, so you got
> > "off", "green", "orange" and "green+orange".
> 
> That's a good example. As long as you can recognize green+orange as
> separate lights/colors
> (w/o magnifying glass) I wouldn't call it "a LED with multiple colors"
> but "multiple
> LED devices".

Well, that's how it is currently handled. But for the user, it looks
as a LED with multiple colors.

> In my use case we talk about RGB LEDs like the commonly used 5050 SMD RGB LEDs.
> And it's not only about using a handful of discrete colors but about
> displaying any arbitrary
> color.
> So far the kernel exposes the physical RGB LEDs as separate LEDs only
> and I can't use
> a trigger to e.g. set "magenta with 50% brightness".

Why not?

What do you do if you want to display magenta on your LCD?

You compute RGB values, then display them.

What would you do for the LEDs? Same thing.

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