[alsa-devel] [PATCH 1/2] ALSA: update sync header when streams are linked/unlinked

Clemens Ladisch clemens at ladisch.de
Wed May 23 21:32:08 CEST 2012

Pierre-Louis Bossart wrote:
>> The fact that the driver currently sets only the card number is
>> actually problematic.  It's not unique enough.  This should be fixed.
>> But, exposing the substream bitmask doesn't help much because it can't
>> be fully implemented in the sync id size.  If you need to know which
>> streams are linked, loop over all streams and check the sync id.
> If I understand you well, the sync id should be a unique identifier
> shared by all linked streams in the same group.

Just to clarify: does the sync id identify streams that are linked, or
streams that can be started atomically when linked?  Because at the
moment, all drivers implement the latter.  Furthermore, it's possible
to link completely unrelated devices, so not even the card number could
be used for the former.


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