[alsa-devel] [PATCH 1/2] snd-usb-audio: Skip un-parseable mixer units instead of erroring

[Jassi Brar]

On 15 April 2012 00:54, Takashi Iwai <tiwai at suse.de> wrote:
> At Sat, 14 Apr 2012 17:19:23 +0100,
> Mark Hills wrote:
>>
>> Some interfaces reference endpoints which do not exists. To
>> accomodate these, do not fail completely, but skip over them.
>>
>> This allows the Electrix Ebox-44 with earlier firmware to be
>> detected and used for audio.
>
> Does the driver warn something?  Ignoring silently doesn't sound
> right...
>
I had been looking into UAC2 device side driver. Debugging
it, enlightened me of the mess the USB audio implementations are in.
IMHO ALSA support usb audio better than AppleUSBAudio ... guess they
are too embarrassed of the code that they no longer keep it public :D

Of course, major blame is on buggy implementation/reporting of configuration
by the devices.

I was wondering if it would make sense for ALSA to first 'mend' any
discrepancies in the reported configuration (say by having optional
callbacks registered against vid/pid), and then instantiate the sound card
which only refers to the cached sanitized configuration ?

That way, we could write usb-audio core to UAC specification, while
keeping vendor specific hacks out separately. Or so do I think.

Regards.
-Jassi