On Fri, Mar 21, 2014 at 11:27 PM, Gerd Hoffmann <kra...@redhat.com> wrote: > Hi, > > I'm thinking about how to handle multihead and multiseat in qemu best. > > On multihead: Mouse in virtual machines works best with absolute > coordinates, and the way this is done today is to assign a (virtual) usb > tablet to the guest. With multihead this becomes a bit difficuilt. > Today we try to calculate the coordinates for the tablet that they cover > all displays, which has a number of drawbacks. I think it would be > better to operate more like a touchscreen, i.e. have one touch input > device for each monitor. For that to work the guest must know which > touch device belongs to which monitor.
Yeah I think I'm in agreement with this, one touch device per monitor, > On multiseat: Very simliar problem here (thats why both issues in one > mail): The guest needs to know which devices belong to which seat. > > Qemu needs the grouping/assignment information too, to the the input > routing right (i.e. input from this window needs to go to that virtual > input device etc). Doing the configuration twice (once for qemu, once > for the guest) and make sure they actually match would be annoying > though. So I think we should configure qemu only, then pass that > information to the guest somehow. > > Question is how to do that best? The GNOME guys have been working on auto config of touch devices, I need to find who is doing that work and what they are triggering on, since X just provides the devices currently, I think we might need some agent in the guest for this. > > I'd like to have some way to assign tags such as seat=foo or head=1 to > devices. Preferably in some way which can easily picked up with udev > rules, so it is easily usable by system-logind and Xorg server. The only current example of seat autoconfiguration is for the usb hubs from displaylink I think, which have video/audio/ethernet/usb behind a hub that udev detects as being part of a seat, I'd need to look up the specifics, > We have virtio devices (virtio-gpu for example). For these it is easy, > we can put something into the virtio protocol, and the guest driver can > create a sysfs file where udev/systemd can pick it up. > > We have pci devices (cirrus for example). One idea for them would be to > create a vendor-specific pci capabiliy for tags. Probably needs some > small utility to read them, or kernel driver support to export them via > sysfs. > > We have usb devices (kbd/mouse/tablet). We could put something into the > string table, or have some vendor-specific descriptor. Same problem > here, not easy accessible, needs a tool or kernel support. > > Comments? Better ideas? Other suggestions? It does seems like tagging the devices somehow would be better than providing a seat device, like we could in theory have a pci and usb controller per seat, and have devices move around between them, this would be like what we for the real hw, however per-device tags does look like it might be nicer in the long run. Dave.
