libata-scsi: be tolerant of 12-byte ATAPI commands in 16-byte CDBs

Sebastian Kemper reported that issuing CD/DVD commands under libata is
not fully compatible with ide-scsi.  In particular, the
GPCMD_SET_STREAMING was being rejected at the host level in some
instances.

The reason is that libata-scsi insists upon the cmd_len field exactly
matching the SCSI opcode being issued, whereas ide-scsi tolerates
12-byte commands contained within a 16-byte (cmd_len) CDB.

There doesn't seem to be a good reason for us to not be compatible
there, so here is a patch to fix libata-scsi to permit SCSI opcodes so
long as they fit within whatever size CDB is provided.
Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Tejun Heo <htejun@gmail.com>

drivers/ata/libata-scsi.c

@@ -2869,7 +2869,8 @@ static inline int __ata_scsi_queuecmd(struct scsi_cmnd *scmd,
 		xlat_func = NULL;
 		if (likely((scsi_op != ATA_16) || !atapi_passthru16)) {
 			/* relay SCSI command to ATAPI device */
-			if (unlikely(scmd->cmd_len > dev->cdb_len))
+			int len = COMMAND_SIZE(scsi_op);
+			if (unlikely(len > scmd->cmd_len || len > dev->cdb_len))
 				goto bad_cdb_len;
 
 			xlat_func = atapi_xlat;