Make struct scsi_status a union

Signed-off-by: Bart Van Assche <bvanassche@acm.org>

drivers/scsi/scsi.c

@@ -768,6 +768,8 @@ static int __init init_scsi(void)
 	int error;
 
 	BUILD_BUG_ON(sizeof(struct scsi_status) != 4);
+	BUILD_BUG_ON(((struct scsi_status){.b = {.status = 4, .msg = 3,
+			.host = 2, .driver = 1}}.combined != 0x01020304));
 	error = scsi_init_procfs();
 	if (error)
 		goto cleanup_queue;

include/scsi/scsi_cmnd.h

@@ -316,22 +316,22 @@ static inline struct scsi_data_buffer *scsi_prot(struct scsi_cmnd *cmd)
 
 static inline void set_status_byte(struct scsi_cmnd *cmd, char status)
 {
-	cmd->result.combined = (cmd->result.combined & 0xffffff00) | status;
+	cmd->result.b.status = status;
 }
 
 static inline void set_msg_byte(struct scsi_cmnd *cmd, char status)
 {
-	cmd->result.combined = (cmd->result.combined & 0xffff00ff) | (status << 8);
+	cmd->result.b.msg = status;
 }
 
 static inline void set_host_byte(struct scsi_cmnd *cmd, char status)
 {
-	cmd->result.combined = (cmd->result.combined & 0xff00ffff) | (status << 16);
+	cmd->result.b.host = status;
 }
 
 static inline void set_driver_byte(struct scsi_cmnd *cmd, char status)
 {
-	cmd->result.combined = (cmd->result.combined & 0x00ffffff) | (status << 24);
+	cmd->result.b.driver = status;
 }
 
 static inline unsigned scsi_transfer_length(struct scsi_cmnd *scmd)

include/scsi/scsi_status.h

@@ -91,9 +91,18 @@ enum driver_status {
  *	- A negative Unix error code.
  *	- In the IDE code, a positive value that represents an error code, an
  *	  error counter or a bitfield.
+ * @b: SCSI status code.
  */
 struct scsi_status {
-	int32_t combined;
+	union {
+		int32_t combined;
+		struct {
+			enum sam_status status	  : 8;
+			enum msg_byte msg	  : 8;
+			enum host_status host	  : 8;
+			enum driver_status driver : 8;
+		} b;
+	};
 };
 
 #endif /* _SCSI_SCSI_STATUS_H */