linux-kernel - Re: "advanced" LED controllers

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Message-ID: <CAMuHMdUUNzFYHzSR3yLCJuz11vuO3Z4yVWVxRQfutGY1KxZLPQ@mail.gmail.com>
Date:	Wed, 25 Feb 2015 09:25:24 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Felipe Balbi <balbi@...com>
Cc:	Bryan Wu <cooloney@...il.com>, Richard Purdie <rpurdie@...ys.net>,
	"linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: Re: "advanced" LED controllers

CC linux-gpio, as this looks like the LED equivalent of bulk gpio?

On Thu, Feb 19, 2015 at 10:14 PM, Felipe Balbi <balbi@...com> wrote:
> Do we have support for LED controllers which can handle patterns of
> different kinds ? I mean, currently, if we have an LED controller such
> as TPIC2810 [1] which can control 8 different leds and each LED
> corresponds to one bit on register 0x44, we could control leds by just
> "playing" a wave file on the controller and create easy patterns with
> that.
>
> AFAICT, in linux today we would have to register each of the 8 LEDs as a
> different LED and have driver magic to write the proper bits on register
> 0x44, that seems a bit overkill, specially when we want to make
> patterns: instead of writing 0xff we would have to write 0x80, 0x40,
> 0x20, 0x10, 0x08, 0x04, 0x02, 0x01 separately and have the driver cache
> the previous results so we don't end up switching off other LEDs.
>
> IOW, what could be handled with a single write, currently needs 8.
>
> I wonder if there's any work happening to support these slightly more
> inteligent LED engines.
>
> regards
>
> [1] http://www.ti.com/product/tpic2810
>
> ps: tpic2810 is probably the simplest example, lp551, lp5523 and others
> have even more advanced pattern engines which can even handle RGB leds.
>
> Currently the driver loads patterns as if it was a firmware blob and
> registers each of R, G and B components as separate LEDs. Each component
> also has its own brightness controls (something tpic2810 doesn't have,
> it's either on or off).
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