Re: [PATCH v2 1/1] video_video: Add the Virtio Video V4L2 driver

Tomasz Figa
2020-03-13T10:05:51Z

On Thu, Mar 12, 2020 at 12:48 PM Dmitry Sepp
<dmitry.sepp@opensynergy.com> wrote:
>
> Hi Hans,
>
> One more thing:
>
> > GFP_DMA? That's unusual. I'd expect GFP_DMA32. All V4L2 drivers use that.
>
> GFP_DMA32 had no effect for me on arm64. Probably I need to recheck.
>

What's the reason to use any specific GFP flags at all? GFP_DMA(32)
memory in the guest would typically correspond to host pages without
any specific location guarantee.

Best regards,
Tomasz

> Best regards,
> Dmitry.
>
> On Donnerstag, 12. März 2020 11:18:26 CET Hans Verkuil wrote:
> > On 3/12/20 11:15 AM, Dmitry Sepp wrote:
> > > Hi Hans,
> > >
> > > Thank you for your great detailed review!
> > >
> > > I won't provide inline answers as your comments totally make sense. There
> > > is>
> > > only one thing I want to mention:
> > >>> + struct video_plane_format plane_format[VIRTIO_VIDEO_MAX_PLANES];
> > >>
> > >> Why is this virtio specific? Any reason for not using VIDEO_MAX_PLANES?
> > >
> > > I'd say this is because VIDEO_MAX_PLANES does not exist outside of the
> > > Linux OS, so for whatever other system we need a virtio specific
> > > definition.
> > OK, good reason :-)
> >
> > It's probably a good thing to add a comment where VIRTIO_VIDEO_MAX_PLANES is
> > defined that explains this.
> >
> > Regards,
> >
> > Hans
>
>