Hi all,

I am using the MOTU Ultralite AVB USB audio interface. With recent
firmwares MOTU uses implicit feedback. Kernel 5.8-rc6 can handle it when
I apply the attached patch with the MOTU signatures.

But both with the old and the new firmware there is an occasional modulo
8 output channel hopping. What goes out to system:playback_1 in jackd
ends on channel 1, 9 or 17 in the interface. Same for system:playback_2.

I can force a hop when changing jackd's buffer size on the fly with
jack_bufsize.

One user reports this issue with ALSA clients, too, so it's probably no
jackd issue.

Since I never found this issue reported from a Windows or Mac user
it may be buried deep in the ALSA kernel code.

For me it seems that flaws/timeouts in the USB communication force this
hopping in the ALSA kernel.

Any ideas how to find out where the hopping happens?
sound/usb/endpoint.c ?
sound/usb/stream.c?

Regards
Holger