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

[Takashi Iwai]

At Wed, 23 May 2012 13:57:34 -0500,
Pierre-Louis Bossart wrote:
> 
> > Also, the point of the sync id is that it's shared with all linked
> > streams.  Your patch breaks it.  It updates only the last added sync
> > id.
> >
> > 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. Since devices can be 
> linked/unlinked, this id cannot use anything related to device or 
> subdevice number. Maybe a pid-like value incremented when a group is 
> created would do?

Yes, that sounds like a reasonable solution.


thanks,

Takashi