HDMI audio on R500

[Russ Dill]

I have a laptop with an HDMI output. In Vista, I can get the Realtek
HD audio driver to pass audio through the HDMI interface. In Linux, no
amount of fiddling with IEC958 switiches and PCM devices will get
audio to come through the HDMI interface.

00:00.0 Host bridge: ATI Technologies Inc RS480 Host Bridge (rev 10)
[...]
00:14.2 Audio device: ATI Technologies Inc IXP SB4x0 High Definition
Audio Controller (rev 01)
[...]
01:00.0 VGA compatible controller: ATI Technologies Inc M56P [Radeon
Mobility X1600]

An alsa developer was thinking that since the video chip interfaces
with the TMDS encoder chip and must somehow be involved. Is anyone
aware of any registers or bits that would enable HDMI audio
pass-through?