--- Gnu-Mach/i386/i386at/kd_queue.h	2020/09/02 04:46:53	1.1.1.2
+++ Gnu-Mach/i386/i386at/kd_queue.h	2020/09/02 04:49:22	1.1.1.3
@@ -64,6 +64,9 @@ WITH THE USE OR PERFORMANCE OF THIS SOFT
  * /dev/mouse.
  */
 
+#ifndef _KD_QUEUE_H_
+#define _KD_QUEUE_H_
+
 #include <mach/std_types.h>
 #include <i386at/kd.h>
 
@@ -76,6 +79,8 @@ typedef struct {
 
 extern void kdq_put(kd_event_queue *, kd_event *);
 extern void kdq_reset(kd_event_queue *);
-extern boolean_t kdq_empty(kd_event_queue *);
-extern boolean_t kdq_full(kd_event_queue *);
+extern boolean_t kdq_empty(const kd_event_queue *);
+extern boolean_t kdq_full(const kd_event_queue *);
 extern kd_event *kdq_get(kd_event_queue *);
+
+#endif /* _KD_QUEUE_H_ */