RE: why is there no enum_input in v4l2_subdev_video_ops

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Hi Laurent,

On Tue, May 10, 2011 at 5:51 PM, Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
> Hi,
>
> On Tuesday 10 May 2011 08:14:10 Hans Verkuil wrote:
>> > On Tue, May 10, 2011 at 5:42 AM, Laurent Pinchart wrote:
>> >>> >> Why is there no enum_input operation in v4l2_subdev_video_ops?
>> >>
>> >> Why do you need one ?
>> >
>> > Because I want to query decoder how many inputs it can support.
>> > So the question is where we should store inputs info, board specific data
>> > or decoder driver?
>> > I appreciate your advice.
>>
>> ENUMINPUT as defined by V4L2 enumerates input connectors available on the
>> board. Which inputs the board designer hooked up is something that only
>> the top-level V4L driver will know. Subdevices do not have that
>> information, so enuminputs is not applicable there.
>>
>> Of course, subdevices do have input pins and output pins, but these are
>> assumed to be fixed. With the s_routing ops the top level driver selects
>> which input and output pins are active. Enumeration of those inputs and
>> outputs wouldn't gain you anything as far as I can tell since the
>> subdevice simply does not know which inputs/outputs are actually hooked
>> up. It's the top level driver that has that information (usually passed in
>> through board/card info structures).
>
> I agree. Subdevs don't have enough knowledge of their surroundings to make
> input enumeration really useful. They could enumerate their input pins, but
> not the inputs that are actually hooked up on board.
>
> The media controller framework is one way of solving this issue. It can report
> links for every input pad.
>
> Scott, can you tell us a bit more about the decoder you're working with ? What
> kind of system is it used in ?

I'm working on ADV7183 and VS6624 connecting with blackfin through ppi.
By the way, ppi is a generic parallel interface, that means it can't know the fmt supported itself.
Should I use enum_mbus_fmt to ask decoder for this info?
I found it in v4l2_subdev_video_ops, but didn't know its usage exactly.

Regards,
Scott


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