Re: [PATCH v4.1 3/3] v4l: Add V4L2_BUF_FLAG_TIMESTAMP_SOF and use it

[Hans Verkuil <hverkuil@xs4all.nl>]

Hi Sakari,

On 01/31/2014 05:42 PM, Sakari Ailus wrote:
> Hi Hans and Laurent,
> 
> On Fri, Jan 31, 2014 at 04:45:56PM +0100, Hans Verkuil wrote:
>> How about defining a capability for use with ENUMINPUT/OUTPUT? I agree that this
>> won't change between buffers, but it is a property of a specific input or output.
> 
> Over 80 characters per line. :-P

Stupid thunderbird doesn't show the column, and I can't enable
automatic word-wrap because that plays hell with patches. Solutions
welcome!

> 
>> There are more than enough bits available in v4l2_input/output to add one for
>> SOF timestamps.
> 
> In complex devices with a non-linear media graph inputs and outputs are not
> very relevant, and for that reason many drivers do not even implement them.
> I'd rather not bind video buffer queues to inputs or outputs.

Then we end up again with buffer flags. It's a property of the selected input
or output, so if you can't/don't want to use that, then it's buffer flags.

Which I like as well, but it's probably useful that the documentation states
that it can only change if the input or output changes as well.

> My personal favourite is still to use controls for the purpose but the
> buffer flags come close, too, especially now that we're using them for
> timestamp sources.

Laurent, can we please end this discussion? It makes perfect sense to store
this information as a BUF_FLAG IMHO. You can just do a QUERYBUF once after
you called REQBUFS and you know what you have to deal with.

Regards,

	Hans