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

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Date:	Mon, 12 Jan 2015 09:32:02 +0100
From:	Jacek Anaszewski <j.anaszewski@...sung.com>
To:	Rob Herring <robherring2@...il.com>
Cc:	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>,
	Pavel Machek <pavel@....cz>, Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>, sakari.ailus@....fi,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	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>
Subject: Re: [PATCH/RFC v10 03/19] DT: leds: Add led-sources property

On 01/09/2015 07:33 PM, Rob Herring wrote:
> On Fri, Jan 9, 2015 at 9:22 AM, Jacek Anaszewski
> <j.anaszewski@...sung.com> wrote:
>> Add a property for defining the device outputs the LED
>> represented by the DT child node is connected to.
>>
>> Signed-off-by: Jacek Anaszewski <j.anaszewski@...sung.com>
>> Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
>> Cc: Bryan Wu <cooloney@...il.com>
>> Cc: Richard Purdie <rpurdie@...ys.net>
>> Cc: Rob Herring <robh+dt@...nel.org>
>> Cc: Pawel Moll <pawel.moll@....com>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: Ian Campbell <ijc+devicetree@...lion.org.uk>
>> Cc: Kumar Gala <galak@...eaurora.org>
>> ---
>>   Documentation/devicetree/bindings/leds/common.txt |    5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/leds/common.txt b/Documentation/devicetree/bindings/leds/common.txt
>> index a2c3f7a..29295bf 100644
>> --- a/Documentation/devicetree/bindings/leds/common.txt
>> +++ b/Documentation/devicetree/bindings/leds/common.txt
>> @@ -1,6 +1,10 @@
>>   Common leds properties.
>>
>>   Optional properties for child nodes:
>> +- led-sources : Array of bits signifying the LED current regulator outputs the
>> +               LED represented by the child node is connected to (1 - the LED
>> +               is connected to the output, 0 - the LED isn't connected to the
>> +               output).
>
> Sorry, I just don't understand this.

In some Flash LED devices one LED can be connected to one or more
electric current outputs, which allows for multiplying the maximum
current allowed for the LED. Each sub-LED is represented by a child
node in the DT binding of the Flash LED device and it needs to declare
which outputs it is connected to. In the example below the led-sources
property is a two element array, which means that the flash LED device
has two current outputs, and the bits signify if the LED is connected
to the output.

Do your doubts stem from the ambiguity of the word "current" or the
form of the description itself is unclear? Probably there should be
explicit explanation added that the size of the array depends on the
number of current outputs of the flash LED device.

>>   - label : The label for this LED.  If omitted, the label is
>>     taken from the node name (excluding the unit address).
>>
>> @@ -33,6 +37,7 @@ system-status {
>>
>>   camera-flash {
>>          label = "Flash";
>> +       led-sources = <1 0>;
>>          max-microamp = <50000>;
>>          flash-max-microamp = <320000>;
>>          flash-timeout-us = <500000>;
>> --
>> 1.7.9.5
>>
>

-- 
Best Regards,
Jacek Anaszewski
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