Re: [PATCH v21 27/39] ASoC: Introduce SND kcontrols to select sound card and PCM device

[Wesley Cheng <quic_wcheng@xxxxxxxxxxx>]

Hi Pierre,

On 5/7/2024 2:26 PM, Pierre-Louis Bossart wrote:
> On 5/7/24 14:51, Wesley Cheng wrote:
> > Add SND kcontrol to SOC USB, which will allow for userpsace to determine
> > which USB card number and PCM device to offload.  This allows for userspace
> > to potentially tag an alternate path for a specific USB SND card and PCM
> > device.  Previously, control was absent, and the offload path would be
> > enabled on the last USB SND device which was connected.  This logic will
> > continue to be applicable if no mixer input is received for specific device
> > selection.
> >
> > An example to configure the offload device using tinymix:
> > tinymix -D 0 set 'USB Offload Playback Route Select' 1 0
> >
> > The above command will configure the offload path to utilize card#1 and PCM
> > stream#0.
>
> I don't know how this is usable in practice. Using card indices is
> really hard to do, it depends on the order in which devices are
> plugged-in...

How are the existing mechanisms handling USB audio devices, or what is 
the identifier being used?

Thanks
Wesley Cheng