On 01/11/2011 06:10 AM, Daniel P. Berrange wrote:
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>
Sounds good, though I think doing <sound model='hda' mic="on|off"/> would be preferable from a UI perspective, since it sounds like that's the only differentiating factor (or maybe use 'duplex' or 'input' etc.). Does that sound okay? - Cole