HDMI sound has to be manually configured in xorg.conf and is switched on for outputs that don't support it (such as internal LCD on laptops).
HDMI sound should be automatically detected.
Linked through from Ubuntu bug https://bugs.edge.launchpad.net/xserver-xorg-driver-radeonhd/+bug/412688
HDMI should not be exposed anymore for outputs like LVDS in current git.
We didn't decide to enable HDMI by default because of some single reports of not working picture transmission after doing so.
Does this issue occur with the preferred ati driver (xf86-vide-ati)? If so, please move this to the Driver/Radeon component.
Development of radeonhd has pretty much halted and development focus is on the ati driver. Please see http://www.x.org/wiki/radeonhd
If the issue does not exist in the ati driver (or if there is no response to this message), this bug will be closed as WONTFIX unless someone contributes a patch.
Closing due to lack of response. Please reopen and move to the Driver/Radeon
component if this issue persists with xf86-video-ati