[Spice-devel] [RFC PATCH v2 00/20] Monitor ID rework

[Gerd Hoffmann]

  Hi,

> > Hmm, why?  I fail to see the point given that qxl wouldn't be able to
> > use it unless you change it too, and all other qemu display devices are
> > either single-head anyway (stdvga, cirrus, ...) or use one channel per
> > head.
> 
> To support streaming of multiple outputs with a single SPICE channel.

aka vgpu multihead.  ok.

> > > although the QXL change would help with Wayland and the bug you
> > > mentioned.
> > 
> > Yes.  I think it would also allow spice protocol changes which are more
> > useful long-term.
> > 
> 
> I would say the opposite, that SPICE changes would allow some long-term QXL
> changes. Which changes do you have in mind?

The issue outlined below.  separate surface creation and output
configuration instead of the "primary surface" concept.  That will
not work with spice protocol changes alone.

> > The fundamental issue is the concept of the "primary surface" which
> > combines defining a surface and defining an output into a single
> > operation.  These need to be separated, so there isn't any special
> > surface.  And any existing surface can be mapped to the output.  Then
> > qxl can pageflip by just mapping a different surface.
> 
> The result won't be different if you transform a video memory region
> into a surface when you want to associate it with an output and will
> easily allows to move drm buffer off/on video memory.

Well, the difference is that the client can't cache the surfaces if you
create and destroy them constantly (and that'll happen with wayland as
it pageflips for every single display update).

cheers,
  Gerd