An AdapterErrorCode indicates that an adapter related error condition occurred. For example, a SCSI operation which completed successfully but resulted in an adapter detected underrun/overrun would report this condition in this field. The error codes used are defined by the IOERR_* codes in the previous section. If no adapter error condition was detected, then this field must be cleared by the ADD driver.
Note: It is possible for a SCSI operation to fail, but this field would be zero. This would be the usual case for target generated error conditions.
Conversely, it is possible for a SCSI operation to succeed at the IORB level, for example, no IORB Error code reported, but this field would non-zero. This would be the case when the SCSI adapter detected an overrun/underrun on an otherwise successful SCSI operation.