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

From: Pavel Machek
Date: Wed Mar 30 2016 - 09:03:29 EST


> >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
> >correction).
> >
> >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".
(cesky, pictures)