[alsa-devel] USB hardware that supports implicit feedback?

Eldad Zack eldad at fogrefinery.com
Thu Nov 15 22:02:45 CET 2012

Hi Daniel,

On Thu, 15 Nov 2012, Daniel Griscom wrote:
> I'm having trouble getting implicit feedback working with my custom
> capture/playback USB audio class device, even with the latest kernel. I
> presume it's a problem with my device's configuration, but can't figure out
> exactly what the problem is (after a whole lotta investigation).

What exactly doesn't work?
The "lsusb -v" output from your device might help here.

> Is there any commercial USB hardware out there that supports implicit
> feedback? I assume the ALSA developers are testing against something, but I
> can't find anything appropriate.

I'm not an ALSA dev, but I recently posted a series of patches for the 
M-Audio Fast Track C400, which uses the implicit feedback code that was 
already in the tree for other devices.
Take a look at sound/usb/pcm.c, there are quite a few hints to how this 
is discovered currently.


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