[alsa-devel] UCM questions

pl bossart bossart.nospam at gmail.com
Thu Jan 20 23:06:55 CET 2011

Hello all,
I've been looking at the UCM code in
git://git.alsa-project.org/alsa-lib.git branch ucm. Looks both
simple/powerfl/useful, still I have a couple of questions (most likely
for Liam and Mark):

- how would a USB device be handled? An audio use case is defined by a
verb and device parameter. My understanding is for a USB headset used
for music playback, we would still use the 'HiFi' verb, but then we
would need a 'USB' device added in include/use-case.h ? Then how would
I make a difference between a USB headset and USB speakers?
- same question for remote displays/display port.
- how useful is the notion of 'card list'? Seems to me that the verbs
are the main entry points, and the notion of card is abstracted away.
For a given use case, the application can query the string containing
the device name. Or I am misled and verbs are only related to a given
- If I want to enable a camcorder use case, possibly with multiple
microphones, do I still use the 'HiFi' verb? Or do we need a new verb
for capture cases? I don't see any mics as capture devices hence the
- how would IEC-formatted data be handled for HDMI/SPDIF? It could be
a different physical device for PCM and IEC-formatted data, and you
would need to enable IEC-related switches in the alsa controls. Or
would a modifier be more appropriate to provide additional information
on the content type?
- has anyone generated a typical configuration file for USB and
HDAudio? I only see an OMAP conf.

Thanks for your feedback

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