The current code writing SADs to the audio registers seems to assume
that there is at most a single SAD per audio format.
However, that is not the case. Especially for PCM it is somewhat common
for sinks to have two SADs, one for 8-channel and one for 2-channel
audio, which may have different supported sample rates (i.e. the sink
supports stereo audio at higher sample rates than multichannel audio).
Because of this, only the 2-channel SAD may be used if it appears before
the 8-channel SAD. Unless other SADs require otherwise, this may cause
the ALSA HDA driver to allow stereo playback only.
Fix the code to pick the PCM SAD with the highest number of channels,
while merging the rate masks of PCM SADs with lower amount of channels
into the additional stereo rate mask byte.
Technically there are even more cases to handle (multiple non-PCM SADs
of the same type, more than two PCM SADs with varying channel counts,
etc), but those have not actually been encountered in the field and
handling them would be non-trivial.
git.openpandora.org / pandora-kernel.git / commitdiff