Re: [PATCH 4/8] ispvideo: Add support for G/S/ENUM_STD ioctl

[Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>]

Mauro Carvalho Chehab wrote:
> Em 27-09-2011 19:41, Laurent Pinchart escreveu:
>> Hi Mauro,
>>
>> On Wednesday 28 September 2011 00:31:32 Mauro Carvalho Chehab wrote:
>>> Em 19-09-2011 12:31, Hiremath, Vaibhav escreveu:
>>>> On Friday, September 16, 2011 6:36 PM Laurent Pinchart wrote: > >> On 
>> Friday 16 September 2011 15:00:53 Ravi, Deepthy wrote:
>>>>>> On Thursday, September 08, 2011 10:51 PM Laurent Pinchart wrote:
>>>>>>> On Thursday 08 September 2011 15:35:22 Deepthy Ravi wrote:
>>>>>>>> From: Vaibhav Hiremath <hvaibhav@ti.com>
>>>>>>>>
>>>>>>>> In order to support TVP5146 (for that matter any video decoder),
>>>>>>>> it is important to support G/S/ENUM_STD ioctl on /dev/videoX
>>>>>>>> device node.
>>>>>>>
>>>>>>> Why so ? Shouldn't it be queried on the subdev output pad directly ?
>>>>>>
>>>>>> Because standard v4l2 application for analog devices will call these
>>>>>> std ioctls on the streaming device node. So it's done on /dev/video to
>>>>>> make the existing apllication work.
>>>>>
>>>>> Existing applications can't work with the OMAP3 ISP (and similar complex
>>>>> embedded devices) without userspace support anyway, either in the form
>>>>> of a GStreamer element or a libv4l plugin. I still believe that analog
>>>>> video standard operations should be added to the subdev pad operations
>>>>> and exposed through subdev device nodes, exactly as done with formats.
>>>>
>>>> I completely agree with your point that, existing application will not
>>>> work without setting links properly. But I believe the assumption here
>>>> is, media-controller should set the links (along with pad formants) and
>>>> all existing application should work as is. Isn't it?
>>>
>>> Yes.
>>>
>>>> The way it is being done currently is, set the format at the pad level
>>>> which is same as analog standard resolution and use existing application
>>>> for streaming...
>>>
>>> Yes.
>>>
>>>> I am ok, if we add s/g/enum_std api support at sub-dev level but this
>>>> should also be supported on streaming device node.
>>>
>>> Agreed. Standards selection should be done at device node, just like any
>>> other device.
>>
>> No. Please see my reply to Vaibhav's e-mail. Standard selection should be done 
>> on the subdev pads, for the exact same reason why formats and selection 
>> rectangles are configured on subdev pads.
> 
> NACK. Let's not reinvent the wheel. the MC should not replace the V4L2 API.

That has never been the intention.

My proposal is that the {G,S,ENUM}_STD is implemented in the V4L2 subdev
user space interface and then the libv4l plugin redirects the call to
the right subdev, in a similar fashion which is planned for V4L2 controls.

Kind regards,

-- 
Sakari Ailus
sakari.ailus@maxwell.research.nokia.com