The routine mrd_scsi_decode(3mrd) is used by the low level MRD
    routines to map SCSI device errors to MRD_STATUS codes. It
    uses the Additional Sense Code (asc) and Additional Sense Code
    Qualifier (ascq) of the status structure to find an appropriate
    MRD_STATUS code. If both the asc and ascq are zero (0), the Sense
    Key (key) will be used to determine the code. The resulting MRD_
    STATUS code will be copied to the code field and returned.

    The routine mrd_map_os_error(3mrd) is used to map operating
    system specific failures to MRD_STATUS codes. If the os_status
    isn't recognized, the routine will return MRD_STATUS_OS_ERROR.
    If the log_info argument is a valid pointer, a copy of the
    operating system text for the message will also copied to the
    space provided.

    This routine uses the dev_status_t structure for handing errors.
    The dev_status_t structure includes the code, os_status, and SCSI
    error fields. The following describes how to decode errors with
    the dev_status_t structure.

    SCSI Errors

    SCSI errors are indicated when the value of the valid field of
    the SCSI error is not equal to 0. The key, asc, and ascq fields
    provide additional information to help determine the cause of the
    error.

    The code usually maps the Additional Sense Code and Additional
    Sense Code Qualifier (ASC/ASCQ) values to an MRD error. The asc
    and ascq values are copied from the request sense data returned
    by the target.

    The Additional Sense Code (asc) indicates further information
    related to the error or exception condition reported in the sense
    key field. The Additional Sense Code Qualifier (ascq) indicates
    detailed information related to the additional sense code. For
    more information, consult the SCSI-2 Specification.

    Operating System Errors

    Operating system errors are indicated when the value of the valid
    field of the SCSI error is equal to 0 and the value of the os_
    status field is not equal to 0. This result is most likely caused
    by an operating system error, and probably has a mapped error in
    MRD.

    MRD Errors

    MRD errors are indicated when the value of the os_status field is
    0, and the value of the valid field of the SCSI error is 0. This
    result is most likely caused when MRD encounters its own failure.