[alsa-devel] [PATCH] snd-usb-audio with multiple audio functions

Clemens Ladisch clemens at ladisch.de
Mon Jun 6 17:47:04 CEST 2011

Rolf Meeser wrote:
> On 06/06/2011 01:44 PM, Clemens Ladisch wrote:
> > Many audio devices with multiple vendor-specific interfaces do not have
> > a control interface.  This code would split them into multiple cards.
> Breaking existing setups would indeed be bad.
> Are that cards with audio interfaces not following the Audio Class spec?


> What would be the easiest way to identify them, so we could assign a new
> card index only in case of a compliant card?

Non-compliant devices don't have a control interface.

In theory, the USB core probes a device's interfaces in order, so the
control interface usually is probed first.  However, I'm not sure if
this is really true for all devices.  It's probably safest to check
explicitly if the device has any interface marked as audio control 1/2.


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