Re: [PATCH v2 3/3] uvcvideo: add a metadata device node

[Guennadi Liakhovetski <g.liakhovetski@gmx.de>]

Hi Laurent,

One more question:

On Tue, 6 Dec 2016, Laurent Pinchart wrote:

> Hi Guennadi,
> 
> On Tuesday 06 Dec 2016 11:39:22 Guennadi Liakhovetski wrote:
> > On Tue, 6 Dec 2016, Laurent Pinchart wrote:
> > > On Monday 05 Dec 2016 23:13:53 Guennadi Liakhovetski wrote:
> > >> On Tue, 6 Dec 2016, Laurent Pinchart wrote:
> > >>>>>> +	/*
> > >>>>>> +	 * Register a metadata node. TODO: shall this only be enabled
> > >>>>>> for some
> > >>>>>> +	 * cameras?
> > >>>>>> +	 */
> > >>>>>> +	if (!(dev->quirks & UVC_QUIRK_BUILTIN_ISIGHT))
> > >>>>>> +		uvc_meta_register(stream);
> > >>>>>> +
> > >>>>> 
> > >>>>> I think so, only for the cameras that can produce metadata.
> > >>>> 
> > >>>> Every UVC camera produces metadata, but most cameras only have standard
> > >>>> fields there. Whether we should stream standard header fields from the
> > >>>> metadata node will be discussed later. If we do decide to stream
> > >>>> standard header fields, then every USB camera gets metadata nodes. If
> > >>>> we decide not to include standard fields, how do we know whether the
> > >>>> camera has any private fields in headers without streaming from it? Do
> > >>>> you want a quirk for such cameras?
> > >>> 
> > >>> Unless they can be detected in a standard way that's probably the best
> > >>> solution.

How about a module parameter with a list of VID:PID pairs? The problem 
with the quirk is, that as vendors produce multiple cameras with different 
PIDs they will have to push patches for each such camera.

Thanks
Guennadi