[alsa-devel] radeon multi-channel lpcm

Pierre Ossman pierre-list at ossman.eu
Fri Aug 31 22:34:47 CEST 2012


I figured I'd have a go at finishing up support for multi-channel lcpm
over HDMI on radeon cards. I read a post from the AMD guys stating that
the GPU portions were already in place, and it was the audio pieces
that were missing. Unfortunately I was unable to figure out exactly what
it is that remains to be done.

I poked around in patch_hdmi.c, and concluded that the generic code is
what's being used for modern radeon cards. The card exposes two widgets
(and output widget and a pin complex). But both widgets indicate
through their capability registers that they only support stereo.

I don't know enough about HDA to have any clue where to go from here.
Should the capability field be ignored for HDMI? Or does it need some
coaxing to allow more than stereo? The ELD stuff isn't properly updated
from the radeon driver, but the code seems to suggest it is just for
hints, and not critical.

     -- Pierre Ossman

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