I picked up a Imation USB SuperDisk drive recently (in vaguely
iMac-blue colors), and was quite pleased that it probed and seems to
work. But it probes a little oddly:

umass0 at uhub0 port 2 configuration 1 interface 0
umass0: Shuttle Technology Inc. E-USB Bridge, rev 1.00/2.00, addr 3
umass0: using SFF8020i over CBI
atapibus0 at umass0 channel 0
sd1 at atapibus0 drive 0: <MATSHITA, LS-120 COSM   04, 0270> type 0 direct removable
sd1: drive offline
sd2 at atapibus0 drive 1: <MATSHITA, LS-120 COSM   04, 0270> type 0 direct removable
sd2: drive offline

[or with a floppy:
atapibus0 at umass0 channel 0
sd1 at atapibus0 drive 0: <MATSHITA, LS-120 COSM   04, 0270> type 0 direct removable
sd1: 1440 KB, 80 cyl, 2 head, 18 sec, 512 bytes/sect x 2880 sectors
sd2 at atapibus0 drive 1: <MATSHITA, LS-120 COSM   04, 0270> type 0 direct removable
sd2: 1440 KB, 80 cyl, 2 head, 18 sec, 512 bytes/sect x 2880 sectors
]

I'm not sure why it probes as both drives. Both drive attachments seem
to work; I can disklabel sd1 or sd2. This looks sort of like the
condition that a SDEV_NOLUNS quirk would handle, but we don't seem to
have an analagous ADEV_* quirk.

Any ideas?

        - Nathan