- remove an extra parenthesis in a closing brace;

- add the macro NETMAP_RING_FIRST_RESERVED() which returns
  the index of the first non-released buffer in the ring
  (this is useful for code that retains buffers for some time
  instead of processing them immediately)

sys/net/netmap_user.h

@@ -77,11 +77,16 @@
 
 #define NETMAP_BUF_IDX(ring, buf)			\
 	( ((char *)(buf) - ((char *)(ring) + (ring)->buf_ofs) ) / \
-		(ring)->nr_buf_size) ) 
+		(ring)->nr_buf_size ) 
 
 #define	NETMAP_RING_NEXT(r, i)				\
 	((i)+1 == (r)->num_slots ? 0 : (i) + 1 )
 
+#define	NETMAP_RING_FIRST_RESERVED(r)			\
+	( (r)->cur < (r)->reserved ?			\
+	  (r)->cur + (r)->num_slots - (r)->reserved :	\
+	  (r)->cur - (r)->reserved )
+
 /*
  * Return 1 if the given tx ring is empty.
  */