Re: [PATCH/RFC 1/2] v4l: Add meta-data video device type

[Mauro Carvalho Chehab <mchehab@osg.samsung.com>]

Em Fri, 22 Apr 2016 16:01:35 +0200
Hans Verkuil <hverkuil@xs4all.nl> escreveu:

> >>>>> + *	%VFL_TYPE_META - Meta-data (including statistics)    
> >>>>
> >>>> I would drop the '(including statistics)' part. It feels weird that
> >>>> 'statistics' are singled out, it makes the reader wonder what is so special
> >>>> about it that it needs to be mentioned explicitly.    
> >>>
> >>> Done.  
> > 
> > It actually makes sense to put statistics as an example of such
> > metadata, as this is the main(and currently only) usage for this
> > devnode.  
> 
> Then I would say 'like statistics' here. 

Fine for me. I would keep it like that.

> But I still don't like this to be
> honest. Heck, Nick Dyer posted a patch series for getting diagnostics yesterday,
> which would be a good fit as well.

Nick patches are interesting. AFAIKT, input devices like touchscreen (and some
trackballs) actually produce a real 2D grey image. In the case of Nick's
patch, it seems that it is a new 16 bits per pixel grey image format:
	+#define V4L2_PIX_FMT_YS16    v4l2_fourcc('Y', 'S', '1', '6') /* signed 16-bit Greyscale */

We need to ask him for mor info, how this is packaged, and what's the
difference from the previously supported formats:
 #define V4L2_PIX_FMT_Y16     v4l2_fourcc('Y', '1', '6', ' ') /* 16  Greyscale     */
 #define V4L2_PIX_FMT_Y16_BE  v4l2_fourcc_be('Y', '1', '6', ' ') /* 16  Greyscale BE  */

IMO, if this is indeed a real image, it should not be using the
metadata buffer format, as this is not metadata, but an image stream.

An interesting question is: in such case, should it use a normal
/dev/video devnode or the new /dev/metadata devnode.

> 
> Anyway, it's not worth a long discussion :-)


-- 
Thanks,
Mauro