The tstdvd binary in ftp://ftp.netbsd.org/pub/incoming/mycroft/dvd-19991031.tgz
works fine on an aic(4) (Adaptec SlimSCSI 1460) against the following two
DVD-RAM drives:

cd0 at scsibus0 targ 0 lun 0: <TOSHIBA, SD-W1101 DVD-RAM, 1033> SCSI2 5/cdrom removable
cd1 at scsibus0 targ 1 lun 0: <MATSHITA, PD-2 LF-D100, A113> SCSI2 5/cdrom removable

but fails against both of the very same drives connected to an isp(4)
(Qlogic 1040B) controller, with the following kernel printfs:

isp0: unsupported cdb length (16, CDB[0]=0xffffffa4)
isp0: unsupported cdb length (16, CDB[0]=0xffffffa4)
isp0: unsupported cdb length (16, CDB[0]=0xffffffa4)
isp0: unsupported cdb length (16, CDB[0]=0xffffffa4)
isp0: unsupported cdb length (16, CDB[0]=0xffffffa4)
isp0: unsupported cdb length (16, CDB[0]=0xffffffa4)
isp0: unsupported cdb length (16, CDB[0]=0xffffffa4)

The output of the failed tstdvd command is:

GetASF failed
N/A, invalidating: Input/output error
N/A, invalidating: Input/output error
N/A, invalidating: Input/output error
Request AGID [1]...     Request AGID [2]...     Request AGID [3]...     Cannot get AGID

Despite this error, the drives perform fine as CD readers and
DVD-RAM reader/writers.  I can mount the ISO9660 partitions fine
on the DVDs, as well.

	Sean.