linux-kernel - "advanced" LED controllers

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Message-ID: <20150219211424.GN13603@saruman.tx.rr.com>
Date:	Thu, 19 Feb 2015 15:14:24 -0600
From:	Felipe Balbi <balbi@...com>
To:	<cooloney@...il.com>, <rpurdie@...ys.net>,
	<linux-leds@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>
Subject: "advanced" LED controllers

Hi,

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).

-- 
balbi

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