linux-kernel - Re: "advanced" LED controllers

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Date:	Mon, 23 Feb 2015 16:58:36 -0600
From:	Felipe Balbi <balbi@...com>
To:	Pavel Machek <pavel@....cz>
CC:	Felipe Balbi <balbi@...com>, <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: Re: "advanced" LED controllers

On Mon, Feb 23, 2015 at 11:34:57PM +0100, Pavel Machek wrote:
> On Thu 2015-02-19 15:14:24, Felipe Balbi wrote:
> > 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.
> 
> Well... some more advanced pattern engines can actually run code, up
> to and including prime number computation. So yes, this is complex,
> and how to handle it nicely is a question...
> 
> I have "notcc" to compile for that.

right, the point is that this is a solution which only works with lp5523
and IMO linux led subsystem should do a little more for such devices.

-- 
balbi

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