scsi: core: Introduce scsi_status_is_check_condition()

Add a helper function scsi_status_is_check_condition() to encapsulate the
frequent checks for SAM_STAT_CHECK_CONDITION.

Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Hannes Reinecke <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/ibmvscsi/ibmvscsi.c

···
 	
 	if (cmnd) {
 		cmnd->result |= rsp->status;
-		if (((cmnd->result >> 1) & 0x1f) == CHECK_CONDITION)
+		if (scsi_status_is_check_condition(cmnd->result))
 			memcpy(cmnd->sense_buffer,
 			       rsp->data,
 			       be32_to_cpu(rsp->sense_data_len));

drivers/scsi/scsi.c

···
 		    (level > 1)) {
 			scsi_print_result(cmd, "Done", disposition);
 			scsi_print_command(cmd);
-			if (status_byte(cmd->result) == CHECK_CONDITION)
+			if (scsi_status_is_check_condition(cmd->result))
 				scsi_print_sense(cmd);
 			if (level > 3)
 				scmd_printk(KERN_INFO, cmd,

drivers/scsi/scsi_error.c

···
 					     current->comm));
 			break;
 		}
-		if (status_byte(scmd->result) != CHECK_CONDITION)
+		if (!scsi_status_is_check_condition(scmd->result))
 			/*
 			 * don't request sense if there's no check condition
 			 * status because the error we're processing isn't one
···
 		return (scmd->request->cmd_flags & REQ_FAILFAST_DRIVER);
 	}
 
-	if (status_byte(scmd->result) != CHECK_CONDITION)
+	if (!scsi_status_is_check_condition(scmd->result))
 		return 0;
 
 check_type:

drivers/scsi/scsi_lib.c

···
 					goto retry;
 				}
 			}
-			if ((status_byte(result) == CHECK_CONDITION) &&
+			if (scsi_status_is_check_condition(result) &&
 			    sshdr->sense_key == UNIT_ATTENTION &&
 			    retry_count) {
 				retry_count--;

include/scsi/scsi.h

···
 	return (lun & 0xff00) == SCSI_W_LUN_BASE;
 }
 
+/**
+ * scsi_status_is_check_condition - check the status return.
+ *
+ * @status: the status passed up from the driver (including host and
+ *          driver components)
+ *
+ * This returns true if the status code is SAM_STAT_CHECK_CONDITION.
+ */
+static inline int scsi_status_is_check_condition(int status)
+{
+	if (status < 0)
+		return false;
+	status &= 0xfe;
+	return status == SAM_STAT_CHECK_CONDITION;
+}
 
 /*
  *  MESSAGE CODES