Re: [virtio-dev] [PATCH] Add virtio gpu specification.

[Gerd Hoffmann <kraxel@redhat.com>]

  Hi,

> > +\item[\field{num_scanouts}] specifies the number of scanouts supported
> > +  by the device
> 
> Please clarify whether this means "the maximum number of scanouts that
> this device is able to support" or "the current number of scanouts
> available"?

Maximum number.  Fixed.  Valid range is 1-16 (added too).

> > +\begin{lstlisting}
> > +#define VIRTIO_GPU_MAX_SCANOUTS 16
> > +struct virtio_gpu_resp_display_info {
> > +        struct virtio_gpu_ctrl_hdr hdr;
> > +        struct virtio_gpu_display_one {
> > +                uint32_t enabled;
> > +                uint32_t width;
> > +                uint32_t height;
> > +                uint32_t x;
> > +                uint32_t y;
> > +                uint32_t flags;
> > +        } pmodes[VIRTIO_GPU_MAX_SCANOUTS];
> 
> Why is pmodes[] a fixed size?  I expected it to have num_scanouts elements.

Didn't look worth the effort allocating this dynamically as num_scanouts
can't become too big.

> > +The response contains a list of per-scanout information.  The info
> > +contains whether the scanout is enabled and what its preferred
> > +position and size is.
> 
> What does "enabled" mean?

Typically this flips from disabled to enabled when the user turns on the
second display (virt-viewer -> menu -> view -> displays -> [x] display
$nr) and it means the guest should use the display.

In the world of physical displays this is the monitor power button:
Turn on monitor -> connector finds link -> state (as seen by xrandr)
goes from "disconnected" to "connected" -> Xorg goes expand your desktop
to the monitor just turned on.

cheers,
  Gerd