[alsa-devel] PCM extra attributes

Raymond Yau superquad.vortex2 at gmail.com
Thu Jul 25 05:54:28 CEST 2013

> We were looking to find the substream index in the userspace for the device
> opened (in case we support multiple substreams and mix them).


snd_pcm_info_get_subdevice() - Get subdevice from a PCM info container

snd_pcm_info_get_subdevice_name() - Get subdevice name from a PCM info

snd_pcm_info_get_subdevice_count() - Get subdevices count from a PCM info

snd_pcm_info_get_subdevice_avail() - Get avail subdevices count from a PCM
info container

snd_pcm_info_set_subdevice - Set wanted subdevice inside a PCM info

> Since we also wanted to have some specific alsa controls for each
> substream the problem of not knowing substream in usermode make stuff
> interesting!

The subdevices of a device need to same format , rate , channels, period
and buffer constraints


More information about the Alsa-devel mailing list