uk —
SCSI user-level driver
uk* at scsibus? target ? lun ?
The uk driver provides support for a process to address
  devices on the SCSI bus for which there is no configured driver.
A SCSI adapter must also be separately configured into the system
    before this driver makes sense.
If a count is given, that number of
  uk devices will be configured into the
  NetBSD kernel.
The uk driver has no ioctls of its own but rather acts
  as a medium for the generic
  scsi(4) ioctls. These are
  described in <sys/scsiio.h>.
  - /dev/uk[0-255]
- unknown SCSI devices.
All scsi(4) debug ioctls work onuk devices.
The uk driver appeared in 386BSD 0.1.