: The drive is reported by NetBSD as not to support a mode sense command.

   Then it is severely broken. The device is asked with a READ CAPACITY
   command about its size, and on any failing command, a MODE SENSE would
   be sent (I guess) to get the exact error code.

Huh?  You're thinking of REQUEST SENSE, which is mandatory, and completely
different.

The driver whines a little if the MODE SENSE command fails to read page 4
(the geometry info).  This is basically harmless, as the geometry isn't
really used for anything.