Re: [libvirt] [PATCH] qemu: sound: Support intel 'hda' model

On Tue, Jan 11, 2011 at 11:46:14AM +0100, Gerd Hoffmann wrote: > On 01/10/11 18:19, Cole Robinson wrote: > >In QEMU, the card itself is a PCI device, but it requires > >-device hda-output in order to actually get sound to the host. AIUI this > >is just HDA configuration and does not require stable addressing, so > >is not presently represented in the XML. > > It isn't that simple. There are actually multiple devices involved. > Each audio codec (yes, there can be multiple of these, up to 15) is > connected via HDA Link to the pci controller. Each audio codec has > a codec address (HDA bus property: cad=[0..14]). > > So you can specify "-device intel-hda -device hda-duplex -device > hda-output" and the guest has multiple audio devices. Win7 even > handles this correctly, whereas alsa uses only the first codec it > finds (lowest codec address). Not that this buys you much today, > qemu mixes all channels together before sending them off to the > hosts sound system, i.e. you don't see a stream per sound card in > pulseaudio. That might change in the future though. > So 'intel-hda' should really be considered as a controller, and hda-output' & 'hda-duplex' are the things to be treated as devices in the guest config. This suggests a setup more like the one we did for virtio-serial where we'd invent a new address type for codecs, and have XML looking something like <controller type='hda' model='ich6'> <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/> </controller> <sound model='hda-output'> <address type='hda' codec='0'/> </sound> <sound model='hda-duplex'> <address type='hda' codec='1'/> </sound> Are there any technical model names for 'hda-output' 'hda-duplex' we need to be aware of (as we potentially have ich6, ich7, 8, 9, etc for intel-hda in the future) > We also might see more hda codecs in the future. Maybe to pass > through digital audio interfaces from the host? Not investigated > yet in detail though. > > The HDA Links are even hot-pluggable (new audio codec can be linked > up when putting the laptop into the docking station for example), > although the qemu emulation doesn't support that today. Hotplug is another good reason for us to treat the 'hda-output' and 'hda-duplex' objects as the <sound> device in libvirt XML, because then we can add/remove them via virDomainAttachDevice which we couldn't otherwise do