[SCSI] Prevent scsi_execute_async from guessing cdb length

When the scsi_execute_async interface was added it ended up reducing
the flexibility of userspace to send arbitrary scsi commands through
sg using SG_IO. The SG_IO interface allows userspace to specify the
CDB length. This is now ignored in scsi_execute_async and it is
guessed using the COMMAND_SIZE macro, which is not always correct,
particularly for vendor specific commands. This patch adds a cmd_len
parameter to the scsi_execute_async interface to allow the caller
to specify the length of the CDB.

Signed-off-by: Brian King <brking@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index e94ca4d..290e3b4 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -275,7 +275,7 @@
 			    int data_direction, void *buffer, unsigned bufflen,
 			    struct scsi_sense_hdr *, int timeout, int retries);
 extern int scsi_execute_async(struct scsi_device *sdev,
-			      const unsigned char *cmd, int data_direction,
+			      const unsigned char *cmd, int cmd_len, int data_direction,
 			      void *buffer, unsigned bufflen, int use_sg,
 			      int timeout, int retries, void *privdata,
 			      void (*done)(void *, char *, int, int),