DIF does not work with 6-byte commands so we previously ignored those
commands when preparing a request.  However, DIX does not need
RDPROTECT/WRPROTECT to be set and 6-byte commands are consequently
perfectly valid in host-only mode.

This patch fixes a problem where we would set the wrong DIX operation
when issuing commands to a legacy disk.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: NMatthew Wilcox <willy@linux.intel.com>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

Switch tag arrays to u8 to prevent problems on platforms with signed
char.
Reported-by: NTim LaBerge <tim.laberge@Quantum.Com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

Add application tag to the output displayed on error.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

For some reason these messages ended up being printed with KERN_INFO
rendering them invisible to pretty much everyone.  Switch to
KERN_NOTICE.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

The old detection code couldn't handle all possible combinations of
DIX and DIF.  This version does, giving priority to DIX if the
controller is capable.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

Now that we no longer use protection_type as trigger for preparing
protected CDBs we can remove the places that set it to zero.  This
allows userland to see which protection type the device is formatted
with regardless of whether the HBA supports DIF or not.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

Support for controllers and disks that implement DIF protection
information:

 - During command preparation the RDPROTECT/WRPROTECT must be set
   correctly if the target has DIF enabled.

 - READ(6) and WRITE(6) are not supported when DIF is on.

 - The controller must be told how to handle the I/O via the
   protection operation field in scsi_cmnd.

 - Refactor the I/O completion code that extracts failed LBA from the
   returned sense data and handle DIF failures correctly.

 - sd_dif.c implements the functions required to prepare and complete
   requests with protection information attached.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>