Regression in SCSI tape detection at boot in 7.2-RELEASE?

[terry+freebsd-stable at tmk.com]

  Sometime between the 7.2-PRERELEASE cycle started and 7.2-RELEASE, 
boot-time probing of tape drives (at least a Quantum DLT8000 and a
Quantum SDLT600) started generating error messages, such as these:

ahc1: <Adaptec 3960D Ultra160 SCSI adapter> port 0xd800-0xd8ff mem 0xfe1fe000-0xfe1fefff irq 25 at device 1.1 on pci2
ahc1: [ITHREAD]
aic7899: Ultra160 Wide Channel B, SCSI Id=7, 32/253 SCBs
...
Waiting 5 seconds for SCSI devices to settle
(probe21:ahc1:0:6:0): TEST UNIT READY. CDB: 0 0 0 0 0 0 
(probe21:ahc1:0:6:0): CAM Status: SCSI Status Error
(probe21:ahc1:0:6:0): SCSI Status: Check Condition
(probe21:ahc1:0:6:0): UNIT ATTENTION asc:29,2
(probe21:ahc1:0:6:0): SCSI bus reset occurred
(probe21:ahc1:0:6:0): Retrying Command (per Sense Data)
(probe21:ahc1:0:6:0): TEST UNIT READY. CDB: 0 0 0 0 0 0 
(probe21:ahc1:0:6:0): CAM Status: SCSI Status Error
(probe21:ahc1:0:6:0): SCSI Status: Check Condition
(probe21:ahc1:0:6:0): UNIT ATTENTION asc:28,0
(probe21:ahc1:0:6:0): Not ready to ready change, medium may have changed
(probe21:ahc1:0:6:0): Retrying Command (per Sense Data)
sa0 at ahc1 bus 0 target 6 lun 0
sa0: <QUANTUM SDLT600 3333> Removable Sequential Access SCSI-4 device 
sa0: 160.000MB/s transfers (80.000MHz DT, offset 120, 16bit)

  This is happening for both stand-alone and loader drives, regardless of
whether there is a tape in the drive at boot time.

  There is no problem with using the drive - no further messages are log-
ged and the drive operates properly.

  Does anyone have any idea what is causing this, and where I should look
to try to track it down?

        Terry Kennedy             http://www.tmk.com
        terry at tmk.com             New York, NY USA