[alsa-devel] Attempting to understand odd snd-usb-audio code and behavior

[Keith A. Milner]

On Wednesday 23 Aug 2017 12:23:00 Clemens Ladisch wrote:
> Keith A. Milner wrote:
> > 
> > It seems to open and close the PCMs
> 
> That happens due to requests from user space, probably PulseAudio.
> 
> > kernel: [ 1987.452947] usb 1-1: Unable to change format on ep #8e: already
> > in use
> So this is a Roland device?  Playback-synchronized-to-capture is a very
> special case; at the moment, nobody understands this code completely.
> 
> But the problem for this device might be that it requires some
> vendor-specific messages to enable it in the first place.

That's very useful, thank you. I forgot about pulseaudio!

So the error messages are due to a userspace app trying to open playback and 
capture at the same time? Or is it just a generic driver/card issue when 
trying to open the interface?

I have the ability to sniff the USB whilst running on Windows. For this 
specific device I may try that.

Regards,

Keith