PROBLEM: (91878, GB_G04640) (PATCH ID: OSF540-056)
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QAR 91878
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This patch adds the capability for KZPCA devices to work with SCSI devices
that only support asynchronous data transfers.
Typically this problem with data transfer negotiation happens during boot and
results in certain SCSI devices not being available after OS boot has completed.
ie- these SCSI devices would be seen at console level but not under Tru64 and
there would be console error messages related to these devices during boot.

Previously ,during data transfer negotiations, the KZPCA would issue a MESSAGE
REJECT message when it received a SYNCHRONOUS DATA TRANSFER REQUEST message
with REQ/ACK offset set to zero from a target. However this is a valid SCSI
transaction indicating that the target does not support synchronous data
transfers with the implied agreement that data transfer mode should be set
to asynchronous mode.

GB_G04640
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Under certain type of tape errors, the SDLT tape drive sends SCSI messages to
the KZPCA adapter which, while still compliant with the SCSI signalling
specifications, are semantically wrong. This causes the adapter to suspend the
SCSI bus for 30+ seconds and reset the bus. The fix in this patch kit prevents
the bus suspension and reset, which is disruptive, from happening and enables
the recovery of the source of error from the tape drive.

SCSI trace shows
546329         299_880 Bus Free
546330           3_300  Arb
546331           2_236  Arbwin 7
546332           0_932 +Select 7,1
546333           0_952 +Sel/Resel End
546334           3_952 +MsgOut C0 Identify
546335          11_652  CMD - Write(6)   <-- KZPCA sends a write to the tape
                         0A 00 00 0F CE 00
546336           4_668  MsgIn  02 Save Data Ptr
                               04 Disconnect <-- tape disconnects to complete
                                                 the operation
546337  72.984_698_496 Bus Free
546338           2_428  Arb
546339           1_364  Arbwin 1
546340           1_232  Resel  7,1  <-- tape reconnects
546341           0_492  Sel/Resel End
546342  37.835_845_308  MsgIn  80 Identify
                               02 Save Data Ptr <<< tape sends a SDP message !
                               04 Disconnect
546343          92_568 Bus Reset <-- KZPCA resets bus after 37 seconds
546344      21_993_576 Bus Free

Problem: tape reconnects, sends and identify then a Save data pointer (SDP)
message. The KZPCA driver is not expecting the SDP message at this point since
it does not make any sense. The code falls into the default handler which
hangs the bus. The bus eventually gets reset.