linux-kernel - Re: [PATCH v4 3/4] drm/virtio: add in/out fence support for explicit synchronization

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Date:   Fri, 9 Nov 2018 11:13:54 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     Emil Velikov <emil.l.velikov@...il.com>
Cc:     Robert Foss <robert.foss@...labora.com>,
        David Airlie <airlied@...ux.ie>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@...ts.linux-foundation.org>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh@...nel.org>,
        Gustavo Padovan <gustavo.padovan@...labora.com>,
        Emil Velikov <emil.velikov@...labora.com>
Subject: Re: [PATCH v4 3/4] drm/virtio: add in/out fence support for explicit
 synchronization

On Mon, Nov 05, 2018 at 05:25:05PM +0000, Emil Velikov wrote:
> On Mon, 5 Nov 2018 at 11:42, Robert Foss <robert.foss@...labora.com> wrote:
> >
> > When the execbuf call receives an in-fence it will get the dma_fence
> > related to that fence fd and wait on it before submitting the draw call.
> >
> > On the out-fence side we get fence returned by the submitted draw call
> > and attach it to a sync_file and send the sync_file fd to userspace. On
> > error -1 is returned to userspace.
> >
> > Signed-off-by: Gustavo Padovan <gustavo.padovan@...labora.com>
> > Signed-off-by: Robert Foss <robert.foss@...labora.com>
> > Suggested-by: Rob Herring <robh@...nel.org>
> > Reviewed-by: Emil Velikov <emil.velikov@...labora.com>
> > ---
> >
> > Changes since v3:
> >  - Move all in_fence handling to the same VIRTGPU_EXECBUF_FENCE_FD_IN block
> Fwiw my suggestion was to explicitly document whether the IOCTL can
> support, simultaneously, IN and OUT fence.

Yes, that would be good.  Code looks like it is supposed to work, but
explicitly saying so in the commit message would be nice.

Also: should we use separate fields for in/out fds?

cheers,
  Gerd