sound over USB

[Ricard Wanderlof]

On Tue, 12 May 2020, Greg KH wrote:

> On Tue, May 12, 2020 at 10:13:10PM +0530, Subhashini Rao Beerisetty wrote:
> > ...
> >  [116677.281756] usbcore: registered new interface driver snd-usb-audio
> >
> >  The following nodes are present in the /dev/snd
> >
> > $ ls -l /dev/snd/
> >
> > total 0
> >
> > drwxr-xr-x 2 root root       60 May 12 11:32 by-id
> >
> > drwxr-xr-x 2 root root       60 May 12 11:32 by-path
> >
> > crw-rw---- 1 root audio 116,  2 May 12 11:32 controlC1
> >
> > crw-rw---- 1 root audio 116,  4 May 12 11:32 pcmC1D0c
> >
> > crw-rw---- 1 root audio 116,  3 May 12 11:32 pcmC1D0p
> >
> > crw-rw---- 1 root audio 116,  1 May 12 11:32 seq
> >
> > crw-rw---- 1 root audio 116, 33 May 12 11:32 timer
> >
> >
> >
> > What are all these devices present in /dev/snd
> >
> > How do I use it for playing and recording an audio?
> >
> > Basically first I want to gain knowledge on set of test cases I can
> > run on ALSA and then learn ALSA kernel modules stuff including
> > snd_usb_audio mdule.
> >
> > So please guide me by providing related documentation/Steps.
> 
> ALSA should "just work" with this device, no need to do anything to the
> kernel driver.  Does it not work properly for you as-is?

To clarify (if it's not too obvious): Normally these devices are never 
accessed directly by programs, instead, there is a userspace library 
called alsa-lib which provides a userspace API and then handles the 
communication with the kernel devices.

/Ricard
-- 
Ricard Wolf Wanderlof                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30