I'm trying to get KMS and HDMI audio working on a 4350. All I see in alsamixer is an S/PDIF device that you can't set the volume on. I'm running Linux 2.6.33 RC6. I'm starting the kernel with...

kernel /kernel root=/dev/sda5 radeon.modeset=1 radeon.audio=1
My understanding is that with KMS enabled I don't need to have X loaded.

It didn't work without KMS and RadeonHD, either.