[Spice-devel] [Qemu-devel] [RFC PATCH spice v2 1/2] QXL interface: add functions to identify monitors in the guest

[Gerd Hoffmann]

On Mon, Nov 05, 2018 at 01:18:57PM +0100, Lukáš Hrázký wrote:
> On Mon, 2018-11-05 at 07:52 +0100, Gerd Hoffmann wrote:
> > > 2. Have a single function as follows:
> > > 
> > > void spice_qxl_set_device_info(QXLInstance *instance,
> > >                                const char *device_address,
> > >                                uint32_t device_display_id_start,
> > >                                uint32_t device_display_id_count);
> > 
> > How about:
> > 
> > void spice_qxl_set_device_info(QXLInstance *instance,
> >                                const char *device_address,
> >                                uint32_t device_display_id);
> > 
> > I don't think we need start+count:
> > 
> >  * For single-head devices device_display_id will be zero.
> >  * For one-channel-per-head multihead devices (i.e. virtio-gpu)
> >    device_display_id will enumerate the heads (so everybody can figure
> >    which channel is which head).
> >  * For one-channel-per-device multihead devices (i.e. qxl/linux)
> >    device_display_id will be zero too.  Number of heads is set via
> >    spice_qxl_set_max_monitors().
> 
> That requires nontrivial and unexpected logic for the one-channel-per-
> device multihead devices case. The API should be doing what it says and
>  the dumber the better, this seems too smart to me...

Well, the device_display_id_count argument is redundant with
spice_qxl_set_max_monitors().  That isn't a great API either.

I can see that it simplifies the logic in spice-server if we have a
single function call instead of two.  So we could deprecate
spice_qxl_set_max_monitors() in favour of your
spice_qxl_set_device_info() variant.

spice_qxl_set_max_monitors() would then basically do this:

    spice_qxl_set_max_monitors(qxl, max)
    {
        spice_qxl_set_device_info(qxl, NULL, 0, max);
    }

cheers,
  Gerd