linux-kernel - Re: [PATCH/RFC v8 08/14] DT: Add documentation for exynos4-is 'flashes' property

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Message-id: <547865EA.5010700@samsung.com>
Date:	Fri, 28 Nov 2014 13:09:14 +0100
From:	Jacek Anaszewski <j.anaszewski@...sung.com>
To:	Mark Rutland <mark.rutland@....com>
Cc:	"linux-leds@...r.kernel.org" <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>,
	"kyungmin.park@...sung.com" <kyungmin.park@...sung.com>,
	"b.zolnierkie@...sung.com" <b.zolnierkie@...sung.com>,
	"pavel@....cz" <pavel@....cz>,
	"cooloney@...il.com" <cooloney@...il.com>,
	"rpurdie@...ys.net" <rpurdie@...ys.net>,
	"sakari.ailus@....fi" <sakari.ailus@....fi>,
	"s.nawrocki@...sung.com" <s.nawrocki@...sung.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH/RFC v8 08/14] DT: Add documentation for exynos4-is
 'flashes' property

On 11/28/2014 12:14 PM, Mark Rutland wrote:
> On Fri, Nov 28, 2014 at 09:18:00AM +0000, Jacek Anaszewski wrote:
>> This patch adds a description of 'flashes' property
>> to the samsung-fimc.txt.
>>
>> Signed-off-by: Jacek Anaszewski <j.anaszewski@...sung.com>
>> Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
>> Cc: Sylwester Nawrocki <s.nawrocki@...sung.com>
>> 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>
>> Cc: <devicetree@...r.kernel.org>
>> ---
>>   .../devicetree/bindings/media/samsung-fimc.txt     |    7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/media/samsung-fimc.txt b/Documentation/devicetree/bindings/media/samsung-fimc.txt
>> index 922d6f8..4b7ed03 100644
>> --- a/Documentation/devicetree/bindings/media/samsung-fimc.txt
>> +++ b/Documentation/devicetree/bindings/media/samsung-fimc.txt
>> @@ -40,6 +40,12 @@ should be inactive. For the "active-a" state the camera port A must be activated
>>   and the port B deactivated and for the state "active-b" it should be the other
>>   way around.
>>
>> +Optional properties:
>> +
>> +- flashes - array of strings with flash led names; the name has to
>> +	    be same with the related led label
>> +	    (see Documentation/devicetree/bindings/leds/common.txt)
>> +
>
> Why is this not an array of phandles to the LED nodes? That's much
> better than strings.

This is because a single flash led device can control many sub-leds,
which are represented by child nodes in the Device Tree.
Every sub-led is registered as a separate LED Flash class device
in the LED subsystem, but in fact they share the same struct device
and thus have access only to the parent's phandle. The LED Flash
class devices are wrapped by V4L2 sub-devices and register
asynchronously within a media device. Since the v4l2_subdev structure
has a 'name' field, it is convenient to initialize it with
parsed 'label' property of a child led node and match the
sub-devices in the media device basing on it.

> Also, I only seem to have recevied the documentation patches and none of
> the code -- in future when posting RFC DT patches, please Cc for the
> code too as it's useful context.

Of course, I'll keep it in mind.

Regards,
Jacek
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