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

[Frediano Ziglio]

> 
> > > Another lousely related thing:  While debugging another issue I've
> > > noticed that QXLMonitorsConfig has a surface_id field.  What this is
> > > intended for?  Map non-primary surface to a head?
> > 
> > I just did a brief investigation, I am not sure. It seems the field is
> > not used in the QEMU <-> SPICE part of the exchange?
> 
> qemu doesn't touch it.
> current linux guest driver never sets this, so it is zero.
> 
> > In the SPICE protocol the field is used to refer to the surface on
> > which the monitor is located. I think it can only be a primary surface
> > and due to implementation limitations this means only surface ID 0, but
> > I may be wrong here. Maybe Frediano has more insight.
> 
> Well, yes, there can be only one primary surface, and the (reserved)
> surface ID for it is 0.
> 

Whomever extended the SPICE protocol (please do not confuse with the
implementation) designed it to have multiple primary surfaces.

> Question is what is supposed to happed in case the ID of another
> (non-primary) surface is placed in that field?
> 
> Tried to do that:
>     https://git.kraxel.org/cgit/linux/log/?h=drm-qxl-wayland-debug
> 
> Looks like it has not the desired effect in spice client ...
> 

Yes, was never implemented.

> > > And one more:  I'm trying to get edid support into qemu and linux kms
> > > drivers.  This might also help identify monitors in the guest (edid data
> > > blobs can have serial numbers).  Not short-term though as this will need
> > > updated guest drivers to work.
> > 
> > We also considered EDID as a possibility for identification, but in the
> > end discarded it as not fitting well. The main reason I think was that
> > EDID is actually data from the physical monitor, not a graphics device
> > output.
> 
> Well, yes, passing through the edid from the physical monitor would not
> work very well I guess.  I'm looking into purely virtual edid data ...
> 
> cheers,
>   Gerd
> 

Apparently from Wayland you can't directly read the serial so you'd have
to use the physical screen size (which you can read), or change Wayland.

Frediano