Does anyone know why otherwise relatively sane hardware would return a
REQUEST_SENSE status in response to a MODE_SENSE command?

This is related to the sc driver I've been working on off and on for a
while.  I've got a disk

sd1 at scsibus0 targ 3 lun 0: <QUANTUM, LP80S  980809404, 3.3> SCSI2 0/direct fixed

that works fine when put on the si.  I've also got an sc driver that
works well enough to use another disk

sd3 at scsibus1 targ 6 lun 0: <RODIME, RO3000S, 2.40> SCSI1 0/direct fixed

just fine.  But when I put the Quantum on the sc, then I get a
REQUEST_SENSE status in response to a command (not surprising), but
then when the driver issues the MODE_SENSE command, it gets
REQUEST_SENSE status from it (very surprising)!

Does anyone have any idea what might be going on here?  No single piece
of the system is blatantly broken - each piece of hardware and software
works fine when used slightly differently - but this combination (the
Quantum disk on the sc with my driver) loses 100% of the time.

					der Mouse

			       mouse@rodents.montreal.qc.ca
		     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B