[...]
and learning abobut it led me to conclude that the Wing needs an entry in the quirks list in set_sync_ep_implicit_fb_quirk to properly enable it:
--- sound/usb/pcm.c.orig 2020-11-22 23:36:08.000000000 +0000 +++ sound/usb/pcm.c 2020-12-05 08:40:21.639600074 +0000 @@ -340,6 +345,7 @@ ep = 0x81; ifnum = 3; goto add_sync_ep_from_ifnum;
case USB_ID(0x1397, 0x050b): /* Behringer Wing */ case USB_ID(0x0763, 0x2080): /* M-Audio FastTrack Ultra */ case USB_ID(0x0763, 0x2081):A week's worth of debugging and learning yielded a one line patch ;)
That's a interesting piece of information :)
Could you give lsusb -v output of the device? With the latest patch set, the driver can set up the implicit feedback mode automatically in certain cases. I'm not sure whether Behringer device follows that pattern. If not, we'd need to add the quirk manually.
I did wonder whether it was possible to automate this, as all I did was looked out the endpoint with the Implicit Feedback flag set. Fingers crossed it'll work.
Output attached.
bjb