Re: [virtio-dev] [RFC RESEND] virtio-video: Add virtio video device specification

[Gerd Hoffmann <kraxel@redhat.com>]

  Hi,

> > Hmm, modern GPUs support both encoding and decoding ...
> 
> Many SoC architectures have completely separate IP blocks for encoding
> and decoding. Similarly, in GPUs those are usually completely separate
> parts of the pipeline.

In the OS there is one driver per GPU handling both ...

> > I don't think we should bake that restriction into the specification.
> > It probably makes sense to use one virtqueue per function though, that
> > will simplify dispatching in both host and guest.
> >
> 
> Wouldn't it make the handling easier if we had one virtio device per function?

I don't think there is much of a difference between one device per
function and one virtqueue per function.  You'll probably have a single
driver for both anyway, to share common code for buffer management etc.

> > Use separate pixel_format (fourcc) and stream_format (H.264 etc.) enums?
> 
> I'd specifically avoid FourCC here, as it's very loosely defined and
> could introduce confusion.

I don't think using fourcc is a problem, and given that both drm and
v4l2 use fourcc already this would be a good choice I think.

But the definition should be more specific than just "fourcc".  Best
would be to explicitly list and define each format supported by the
spec.

cheers,
  Gerd