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



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


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