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>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 94144ed50a6b..a45f6ac3b245 100644
--- a/drivers/ata/libata-scsi.c
+++ b/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;