linux-kernel - Re: [PATCH RFC v3] media: OF: add video sync endpoint property

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Message-ID: <51E2FAB3.3060409@gmail.com>
Date:	Sun, 14 Jul 2013 21:23:31 +0200
From:	Sylwester Nawrocki <sylvester.nawrocki@...il.com>
To:	Prabhakar Lad <prabhakar.csengg@...il.com>
CC:	Sylwester Nawrocki <sylvester.nawrocki@...il.com>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	LMML <linux-media@...r.kernel.org>,
	Hans Verkuil <hans.verkuil@...co.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	DLOS <davinci-linux-open-source@...ux.davincidsp.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Guennadi Liakhovetski <g.liakhovetski@....de>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Sakari Ailus <sakari.ailus@....fi>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>
Subject: Re: [PATCH RFC v3] media: OF: add video sync endpoint property

Hi Prabhakar,

On 07/12/2013 06:29 AM, Prabhakar Lad wrote:
> On Fri, Jul 12, 2013 at 2:45 AM, Sylwester Nawrocki
> <sylvester.nawrocki@...il.com>  wrote:
>> On 07/11/2013 01:41 PM, Prabhakar Lad wrote:
>> [...]
>>
>>>>> diff --git a/drivers/media/v4l2-core/v4l2-of.c
>>>>> b/drivers/media/v4l2-core/v4l2-of.c
>>>>> index aa59639..1a54530 100644
>>>>> --- a/drivers/media/v4l2-core/v4l2-of.c
>>>>> +++ b/drivers/media/v4l2-core/v4l2-of.c
>>>>> @@ -100,6 +100,26 @@ static void v4l2_of_parse_parallel_bus(const struct
>>>>> device_node *node,
>>>>>           if (!of_property_read_u32(node, "data-shift",&v))
>>>>>                   bus->data_shift = v;
>>>>>
>>>>> +       if (!of_property_read_u32(node, "video-sync",&v)) {
>>>>> +               switch (v) {
>>>>> +               case V4L2_MBUS_VIDEO_SEPARATE_SYNC:
>>>>> +                       flags |= V4L2_MBUS_VIDEO_SEPARATE_SYNC;
>>>>
>>>>
>>>>
>>>> I'm not convinced all those video sync types is something that really
>>>> belongs
>>>> to the flags field. In my understanding this field is supposed to hold
>>>> only
>>>> the _signal polarity_ information.
>>>>
>>>>
>>> Ok, so there should be a function say v4l2_of_parse_signal_polarity()
>>> to get the polarity alone then.
>>
>>
>> I don't think this is required, I would just extend
>> v4l2_of_parse_parallel_bus()
>> function to also handle sync-on-green-active property.
>>
> If that is the case than I have to add a member say 'signal_polarity'
> in struct v4l2_of_bus_parallel and assign the polarity to it.
> Let me know if you are OK with it.

It probably would have been sensible to do something like this, however 
I can't
see any advantage at the moment. struct v4l2_of_bus_parallel::flags 
currently
holds all the polarity flags. Let's just add relevant macros for 
sync-on-green
and store them in the flags field, as is done with the others.
Those V4L2_MUS_* flags are used by soc-camera to negotiate the 
capabilities,
so I would rather not split them further without good reason, even though
struct v4l2_mbus_config::flags is used in those negotiation routines, 
rather
than struct v4l2_of_bus_parallel::flags.

--
Thanks,
Sylwester


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