diff --git a/sys/net/bpf.h b/sys/net/bpf.h
index 50ed0b91a42e..0c905f1e5cc0 100644
--- a/sys/net/bpf.h
+++ b/sys/net/bpf.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: bpf.h,v 1.64 2014/06/24 10:53:30 alnsn Exp $	*/
+/*	$NetBSD: bpf.h,v 1.65 2014/06/24 22:19:36 rmind Exp $	*/
 
 /*
  * Copyright (c) 1990, 1991, 1993
@@ -280,19 +280,16 @@ struct bpf_insn {
 /*
  * Number of scratch memory words (for BPF_LD|BPF_MEM and BPF_ST).
  */
-#define	BPF_MEMWORDS	16
+#define	BPF_MEMWORDS		16
 
 /*
- * Each bit in bpf_memword_init_t value indicates if the corresponding
- * external memory word is initialised prior to calling a bpf program.
- * Note that when used internally, a meaning is often flipped: bits
- * indicate which memory words need to be initialised prior to
- * executing a bpf program.
+ * bpf_memword_init_t: bits indicate which words in the external memory
+ * store will be initialised by the caller before BPF program execution.
  */
 typedef uint32_t bpf_memword_init_t;
-#define BPF_MEMWORD_INIT(k) (UINT32_C(1) << (k))
+#define	BPF_MEMWORD_INIT(k)	(UINT32_C(1) << (k))
 
-/* Two most significant bits are reserved by bpfjit. */
+/* Note: two most significant bits are reserved by bpfjit. */
 __CTASSERT(BPF_MEMWORDS + 2 <= sizeof(bpf_memword_init_t) * NBBY);
 
 #ifdef _KERNEL
@@ -300,13 +297,10 @@ __CTASSERT(BPF_MEMWORDS + 2 <= sizeof(bpf_memword_init_t) * NBBY);
  * Max number of external memory words (for BPF_LD|BPF_MEM and BPF_ST).
  */
 #define	BPF_MAX_MEMWORDS	30
-__CTASSERT(BPF_MAX_MEMWORDS >= BPF_MEMWORDS);
 
-#ifdef __BPF_PRIVATE
-/* Two most significant bits are reserved by bpfjit. */
+__CTASSERT(BPF_MAX_MEMWORDS >= BPF_MEMWORDS);
 __CTASSERT(BPF_MAX_MEMWORDS + 2 <= sizeof(bpf_memword_init_t) * NBBY);
 #endif
-#endif
 
 /*
  * Structure to retrieve available DLTs for the interface.
@@ -319,10 +313,7 @@ struct bpf_dltlist {
 struct bpf_ctx;
 typedef struct bpf_ctx bpf_ctx_t;
 
-struct bpf_args;
-typedef struct bpf_args bpf_args_t;
-
-struct bpf_args {
+typedef struct bpf_args {
 	const uint8_t *	pkt;
 	size_t		wirelen;
 	size_t		buflen;
@@ -336,21 +327,32 @@ struct bpf_args {
 	 */
 	uint32_t *	mem; /* pointer to external memory store */
 	void *		arg; /* auxiliary argument for a copfunc */
-};
+} bpf_args_t;
 
 #if defined(_KERNEL) || defined(__BPF_PRIVATE)
+
 typedef uint32_t (*bpf_copfunc_t)(const bpf_ctx_t *, bpf_args_t *, uint32_t);
 
 struct bpf_ctx {
+	/*
+	 * BPF coprocessor functions and the number of them.
+	 */
 	const bpf_copfunc_t *	copfuncs;
 	size_t			nfuncs;
+
 	/*
-	 * Number of external memwords, up to BPF_MAX_MEMWORDS or 0.
-	 * The latter forces a switch to internal memstore with a
-	 * fixed number (BPF_MEMWORDS) of memwords.
+	 * The number of memory words in the external memory store.
+	 * There may be up to BPF_MAX_MEMWORDS words; if zero is set,
+	 * then the internal memory store is used which has a fixed
+	 * number of words (BPF_MEMWORDS).
 	 */
 	size_t			extwords;
-	bpf_memword_init_t	noinit; /* pre-initialised external memwords */
+
+	/*
+	 * The bitmask indicating which words in the external memstore
+	 * will be initialised by the caller.
+	 */
+	bpf_memword_init_t	preinited;
 };
 #endif
 
@@ -447,20 +449,20 @@ bpf_mtap_sl_out(struct ifnet *_ifp, u_char *_hdr, struct mbuf *_m)
 }
 
 
-void     bpf_setops(void);
+void	bpf_setops(void);
 
-void     bpf_ops_handover_enter(struct bpf_ops *);
-void     bpf_ops_handover_exit(void);
+void	bpf_ops_handover_enter(struct bpf_ops *);
+void	bpf_ops_handover_exit(void);
 
-void	 bpfilterattach(int);
+void	bpfilterattach(int);
 
 bpf_ctx_t *bpf_create(void);
 void	bpf_destroy(bpf_ctx_t *);
 
-int   bpf_set_cop(bpf_ctx_t *, const bpf_copfunc_t *, size_t);
-int   bpf_set_extmem(bpf_ctx_t *, size_t, bpf_memword_init_t);
-u_int bpf_filter_ext(const bpf_ctx_t *, const struct bpf_insn *, bpf_args_t *);
-int   bpf_validate_ext(const bpf_ctx_t *, const struct bpf_insn *, int);
+int	bpf_set_cop(bpf_ctx_t *, const bpf_copfunc_t *, size_t);
+int	bpf_set_extmem(bpf_ctx_t *, size_t, bpf_memword_init_t);
+u_int	bpf_filter_ext(const bpf_ctx_t *, const struct bpf_insn *, bpf_args_t *);
+int	bpf_validate_ext(const bpf_ctx_t *, const struct bpf_insn *, int);
 
 bpfjit_func_t bpf_jit_generate(bpf_ctx_t *, void *, size_t);
 void	bpf_jit_freecode(bpfjit_func_t);
diff --git a/sys/net/bpf_filter.c b/sys/net/bpf_filter.c
index ef47cb13d237..03226c29c134 100644
--- a/sys/net/bpf_filter.c
+++ b/sys/net/bpf_filter.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: bpf_filter.c,v 1.62 2014/06/24 10:53:30 alnsn Exp $	*/
+/*	$NetBSD: bpf_filter.c,v 1.63 2014/06/24 22:19:36 rmind Exp $	*/
 
 /*-
  * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: bpf_filter.c,v 1.62 2014/06/24 10:53:30 alnsn Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bpf_filter.c,v 1.63 2014/06/24 22:19:36 rmind Exp $");
 
 #if 0
 #if !(defined(lint) || defined(KERNEL))
@@ -82,7 +82,7 @@ bpf_set_extmem(bpf_ctx_t *bc, size_t nwords, bpf_memword_init_t preinited)
 	/* XXX check arguments */
 
 	bc->extwords = nwords;
-	bc->noinit = preinited;
+	bc->preinited = preinited;
 	return 0;
 }
 
@@ -591,9 +591,9 @@ bpf_validate(const struct bpf_insn *f, int signed_len)
 #if defined(KERNEL) || defined(_KERNEL)
 	bpf_memword_init_t *mem, invalid;
 	size_t size;
-	const size_t extwords = (bc != NULL) ? bc->extwords : 0;
-	const size_t memwords = (extwords != 0) ? extwords : BPF_MEMWORDS;
-	const bpf_memword_init_t noinit = (extwords != 0) ? bc->noinit : 0;
+	const size_t extwords = bc ? bc->extwords : 0;
+	const size_t memwords = extwords ? extwords : BPF_MEMWORDS;
+	const bpf_memword_init_t preinited = extwords ? bc->preinited : 0;
 #else
 	const size_t memwords = BPF_MEMWORDS;
 #endif
@@ -609,8 +609,9 @@ bpf_validate(const struct bpf_insn *f, int signed_len)
 		return 0;
 
 #if defined(KERNEL) || defined(_KERNEL)
+	/* Note: only the pre-initialised is valid on startup */
 	mem = kmem_zalloc(size = sizeof(*mem) * len, KM_SLEEP);
-	invalid = ~noinit; /* Only pre-initialised memory is valid on startup */
+	invalid = ~preinited;
 #endif
 
 	for (i = 0; i < len; ++i) {
diff --git a/sys/net/bpfjit.c b/sys/net/bpfjit.c
index 8fe94836b454..058c0073b100 100644
--- a/sys/net/bpfjit.c
+++ b/sys/net/bpfjit.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: bpfjit.c,v 1.13 2014/06/24 10:53:30 alnsn Exp $	*/
+/*	$NetBSD: bpfjit.c,v 1.14 2014/06/24 22:19:36 rmind Exp $	*/
 
 /*-
  * Copyright (c) 2011-2014 Alexander Nasonov.
@@ -31,9 +31,9 @@
 
 #include <sys/cdefs.h>
 #ifdef _KERNEL
-__KERNEL_RCSID(0, "$NetBSD: bpfjit.c,v 1.13 2014/06/24 10:53:30 alnsn Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bpfjit.c,v 1.14 2014/06/24 22:19:36 rmind Exp $");
 #else
-__RCSID("$NetBSD: bpfjit.c,v 1.13 2014/06/24 10:53:30 alnsn Exp $");
+__RCSID("$NetBSD: bpfjit.c,v 1.14 2014/06/24 22:19:36 rmind Exp $");
 #endif
 
 #include <sys/types.h>
@@ -1611,9 +1611,9 @@ bpfjit_generate_code(const bpf_ctx_t *bc,
 
 	uint32_t jt, jf;
 
-	const size_t extwords = (bc != NULL) ? bc->extwords : 0;
-	const size_t memwords = (extwords != 0) ? extwords : BPF_MEMWORDS;
-	const bpf_memword_init_t noinit = (extwords != 0) ? bc->noinit : 0;
+	const size_t extwords = bc ? bc->extwords : 0;
+	const size_t memwords = extwords ? extwords : BPF_MEMWORDS;
+	const bpf_memword_init_t preinited = extwords ? bc->preinited : 0;
 
 	rv = NULL;
 	ret0 = NULL;
@@ -1690,9 +1690,9 @@ bpfjit_generate_code(const bpf_ctx_t *bc,
 	/*
 	 * Exclude pre-initialised external memory words but keep
 	 * initialization statuses of A and X registers in case
-	 * bc->noinit wrongly sets those two bits.
+	 * bc->preinited wrongly sets those two bits.
 	 */
-	initmask &= ~noinit | BJ_INIT_ABIT | BJ_INIT_XBIT;
+	initmask &= ~preinited | BJ_INIT_ABIT | BJ_INIT_XBIT;
 
 #if defined(_KERNEL)
 	/* bpf_filter() checks initialization of memwords. */