linux-kernel - Re: [PATCH/RFC v10 03/19] DT: leds: Add led-sources property

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Date:	Fri, 16 Jan 2015 11:17:24 +0100
From:	Sylwester Nawrocki <s.nawrocki@...sung.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Mark Brown <broonie@...nel.org>,
	Rob Herring <robherring2@...il.com>,
	Jacek Anaszewski <j.anaszewski@...sung.com>,
	linux-leds@...r.kernel.org,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>, sakari.ailus@....fi,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Liam Girdwood <lgirdwood@...il.com>
Subject: Re: [PATCH/RFC v10 03/19] DT: leds: Add led-sources property

Hi,

On 15/01/15 22:03, Pavel Machek wrote:
>> Perhaps we could use the 'reg' property to describe actual connections,
>> > I'm not sure if it's better than a LED specific property, e.g.
>> > 
>> > max77387@52 {
>> >         compatible = "nxp,max77387";
>> >         #address-cells = <2>;
>> >         #size-cells = <0>;
>> >         reg = <0x52>;
>> > 
>> > 	flash_led {
>> > 		reg = <1 1>;	
>> > 		...
>> > 	};	
>> > };
>
> Normally, reg property is <start length>, if I understand things
> correctly? Would that be enough here, or would we be doing list of
> outputs?

In general the exact meaning depends on value of the #address-cells and
#size-cells properties in the parent node.  In case as above #size-cells
is 0.  You can find exact explanation in [1], at page 25.

Anyway, the above example might an abuse of the simple bus. I thought more
about a list of outputs, but the indexes wouldn't be contiguous, e.g.

 curr. reg. outputs | "addres" value
--------------------------------
FLED2    FLED1      |  reg
--------------------+-----------
  0        1        | 0x00000001
  1        0        | 0x00010000
  1        1        | 0x00010001

But it might be not a good idea as Rob pointed out.

OTOH we could simply assign indices 1,2,3 to the above FLED1/2 output
combinations.

[1] https://www.power.org/wp-content/uploads/2012/06/Power_ePAPR_APPROVED_v1.1.pdf

--
Regards,
Sylwester
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