Re: [PATCH v5 1/4] leds: core: add generic support for RGB Color LED's
From: Heiner Kallweit
Date: Wed Mar 30 2016 - 10:00:07 EST
On Wed, Mar 30, 2016 at 3:03 PM, Pavel Machek <pavel@xxxxxx> wrote:
>> >Ok, so:
>> >a) Do we want RGB leds to be handled by existing subsystem, or do we
>> >need separate layer on top of that?
>> >b) Does RGB make sense, or HSV? RGB is quite widely used in graphics,
>> >and it is what hardware implements. (But we'd need to do gamma
>> >c) My hardware has "acceleration engine", LED is independend from
>> >CPU. That's rather big deal. Does yours? It seems to be quite common,
>> >at least in cellphones.
>> >Ideally, I'd like to have "triggers", but different ones. As in: if
>> >charging, do yellow " .xX" pattern. If fully charged, do green steady
>> >light. If message is waiting, do blue " x x" pattern. If none of
>> >above, do slow white blinking. (Plus priorities of events). But that's
>> >quite different from existing support...)
>> Please note that HSV colour scheme allows to neatly project monochrome
>> brightness semantics on the RGB realm. I.e. you can have fixed
>> hue and saturation, and by changing the brightness component a perceived
>> colour intensity can be altered.
> I see HSV has some advantages. But we already have LEDs with multiple
> colors, and kernel already handles them:
> pavel@duo:~$ ls -1 /sys/class/leds/
> 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
(w/o magnifying glass) I wouldn't call it "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
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".
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html