[alsa-devel] right way to enumerate pcm devices

[Takashi Iwai]

On Tue, 12 Feb 2019 21:33:24 +0100,
sylvain.bertrand at gmail.com wrote:
> 
> On Tue, Feb 12, 2019 at 02:36:00PM +0100, Takashi Iwai wrote:
> > The entries without hints are filtered out as default.
> > i.e. a user-defined entry appears, too, if it contains the hints.
> > 
> > You can change the behavior by setting defaults.namehint.showall,
> > too.
> 
> Hi again,
> 
> I am listing the pcm devices, and for the USB mic of my webcam, I get input
> (IOID=Input) pcm devices for surroundX/frontspeakers/IEC958, which are
> actually output pcm devices.
> Why those output pcm devices are hinted as input devices?? Is this expected?
> Bug? If not, how am I supposed to select the proper input pcm devices the
> right(tm) way ?

It's only the matter of alsa-lib card config.  Just due to heuristic
reason, the secondary device is assigned as iec958 as default.  There
are explicit whitelist setup in alsa-lib/src/conf/cards/USB-Audio.conf
for the card that behave differently.  You'd need to adjust
accordingly.


Takashi