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

Keiichi Watanabe
2019-12-09T13:18:09Z

Hi,

On Mon, Dec 9, 2019 at 8:38 PM Dmitry Sepp <dmitry.sepp@opensynergy.com> wrote:
>
> Hi,
>
> On Montag, 9. Dezember 2019 11:46:15 CET Gerd Hoffmann wrote:
> > Hi,
> >
> > > > For (1) you'll simply do a QUEUE_BUFFER. The command carries references
> > > > to the buffer pages. No resource management needed.
> > > >
> > > > For (2) you'll have RESOURCE_CREATE + RESOURCE_DESTROY + QUEUE_RESOURCE,
> > > > where RESOURCE_CREATE passes the scatter list of buffer pages to the
> > > > host and QUEUE_RESOURCE will carry just the resource id.
> > > >
> > > > For (3) you'll have RESOURCE_IMPORT + RESOURCE_DESTROY + QUEUE_RESOURCE.
> > >
> > > Thanks for the clarification.
> > > On second thought, however, I'm wondering if we should keep all
> > > RESOURCE controls.
> > > This should be an option (4).
> >
> > Well, that's actually (2), aka "we use RESOURCE_* commands to manage
> > resources". With the commands in the latest draft that would be:
> >
> > (1) RESOURCE_CREATE
> > (2) RESOURCE_ATTACH_BACKING
> > (3) RESOURCE_QUEUE (resource can be used multiple times here)
> > (4) RESOURCE_DETACH_BACKING
> > (5) RESOURCE_DESTROY
> >
> > I'm not sure we need the separate *_BACKING commands. I think we could
> > also have RESOURCE_CREATE pass the buffer pages scatter list instead.
> >
> > Why it is done this way? Just because the design was copied from
> > virtio-gpu? Or is there some specific reason?
>
> Yes, the design was just derived from virtio-gpu at early stages.
>
> I do agree we should merge the two steps.

Thanks for the explanation. Merging them sounds good to me.

-Keiichi

>
> >
> > cheers,
> > Gerd
>
>