M-Audio Fast Track Ultra 8R

I got my hands on an M-Audio Fast Track Ultra 8R,
an USB audio interface; eight tracks, 24/96, nice.
It attaches like this on FreeBSD:

ugen0.6: <M-Audio Fast Track Ultra 8R> at usbus0
uaudio0 on uhub2
uaudio0: <M-Audio Fast Track Ultra 8R, class 239/2, rev 2.00/1.51, addr 6> on usbus0
uaudio0: Play[0]: 96000 Hz, 8 ch, 24-bit S-LE PCM format, 2x4ms buffer. (selected)
uaudio0: Play[0]: 88200 Hz, 8 ch, 24-bit S-LE PCM format, 2x4ms buffer.
uaudio0: Play[0]: 48000 Hz, 8 ch, 24-bit S-LE PCM format, 2x4ms buffer.
uaudio0: Play[0]: 44100 Hz, 8 ch, 24-bit S-LE PCM format, 2x4ms buffer.
uaudio0: Record[0]: 96000 Hz, 8 ch, 24-bit S-LE PCM format, 2x4ms buffer. (selected)
uaudio0: Record[0]: 88200 Hz, 8 ch, 24-bit S-LE PCM format, 2x4ms buffer.
uaudio0: Record[0]: 48000 Hz, 8 ch, 24-bit S-LE PCM format, 2x4ms buffer.
uaudio0: Record[0]: 44100 Hz, 8 ch, 24-bit S-LE PCM format, 2x4ms buffer.
uaudio0: Single command MIDI quirk enabled
uaudio0: MIDI sequencer.
pcm3 on uaudio0
uaudio0: No HID volume keys found.

Everything seems to work, recording the 8 channels.

The device doesn't seem to be USB class-compliamt, though.
Class 239 (= 0xef) is "miscelaneous", i.e. not audio, which is 0x01.
https://en.wikipedia.org/wiki/USB#Device_classes

I am trying to make this work on OpenBSD
https://marc.info/?l=openbsd-misc&m=171972890415337&w=2
where it only attaches as ugen, not uaudio.

I would like to learn here what it is that FreeBSD does
while trying to attach the device, given that it is, apparently,
not an adio-class compliant device.

Is there a quirk that makes the kernel go
"oh, but it is actualy USN audio device, even
if it does not report as such; act accordingly"?

Please excuse my ignorance. Where in the FreeBSD code can I look
at the driver and see how exactly the device gets treated?

	Thank you

		Jan

PS: M-Audio themselves have left users in the cold, abandoning the device.
https://avidtech.my.salesforce-sites.com/pkb/articles/en_US/Knowledge/Fast-Track-Ultra-8R-Drivers