diff --git a/sys/alpha/include/bus.h b/sys/alpha/include/bus.h
index 7fe2726736a..1810c4b5306 100644
--- a/sys/alpha/include/bus.h
+++ b/sys/alpha/include/bus.h
@@ -364,6 +364,18 @@ void busspace_generic_barrier(struct alpha_busspace *space,
 #define bus_space_barrier(t, h, o, l, f) \
 	(t)->ab_ops->abo_barrier(t, (h)+(o), l, f)
 
+#define barrier_read \
+	bus_space_barrier(busspace_isa_mem, 0, BUS_SPACE_UNRESTRICTED,	\
+	    BUS_SPACE_BARRIER_READ)
+
+#define barrier_write \
+	bus_space_barrier(busspace_isa_mem, 0, BUS_SPACE_UNRESTRICTED,	\
+	    BUS_SPACE_BARRIER_WRITE)
+
+#define barrier_rw \
+	bus_space_barrier(busspace_isa_mem, 0, BUS_SPACE_UNRESTRICTED,	\
+	    BUS_SPACE_BARRIER_READ | BUS_SPACE_BARRIER_WRITE)
+
 /*
  * Flags used in various bus DMA methods.
  */
diff --git a/sys/amd64/include/bus_amd64.h b/sys/amd64/include/bus_amd64.h
index 2d84400e8bd..3423e6b1ad4 100644
--- a/sys/amd64/include/bus_amd64.h
+++ b/sys/amd64/include/bus_amd64.h
@@ -1153,6 +1153,29 @@ bus_space_barrier(bus_space_tag_t tag, bus_space_handle_t bsh,
 }
 	
 
+/*
+ * Generic memory barrier functions.
+ */
+static __inline void
+barrier_read(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0, BUS_SPACE_BARRIER_READ);
+}
+
+static __inline void
+barrier_write(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_WRITE);
+}
+
+static __inline void
+barrier_rw(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_READ | BUS_SPACE_BARRIER_WRITE);
+}
+
 /*
  * Flags used in various bus DMA methods.
  */
diff --git a/sys/amd64/include/bus_at386.h b/sys/amd64/include/bus_at386.h
index 2d84400e8bd..3423e6b1ad4 100644
--- a/sys/amd64/include/bus_at386.h
+++ b/sys/amd64/include/bus_at386.h
@@ -1153,6 +1153,29 @@ bus_space_barrier(bus_space_tag_t tag, bus_space_handle_t bsh,
 }
 	
 
+/*
+ * Generic memory barrier functions.
+ */
+static __inline void
+barrier_read(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0, BUS_SPACE_BARRIER_READ);
+}
+
+static __inline void
+barrier_write(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_WRITE);
+}
+
+static __inline void
+barrier_rw(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_READ | BUS_SPACE_BARRIER_WRITE);
+}
+
 /*
  * Flags used in various bus DMA methods.
  */
diff --git a/sys/amd64/include/bus_dma.h b/sys/amd64/include/bus_dma.h
index 2d84400e8bd..3423e6b1ad4 100644
--- a/sys/amd64/include/bus_dma.h
+++ b/sys/amd64/include/bus_dma.h
@@ -1153,6 +1153,29 @@ bus_space_barrier(bus_space_tag_t tag, bus_space_handle_t bsh,
 }
 	
 
+/*
+ * Generic memory barrier functions.
+ */
+static __inline void
+barrier_read(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0, BUS_SPACE_BARRIER_READ);
+}
+
+static __inline void
+barrier_write(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_WRITE);
+}
+
+static __inline void
+barrier_rw(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_READ | BUS_SPACE_BARRIER_WRITE);
+}
+
 /*
  * Flags used in various bus DMA methods.
  */
diff --git a/sys/i386/include/bus_at386.h b/sys/i386/include/bus_at386.h
index 2d84400e8bd..3423e6b1ad4 100644
--- a/sys/i386/include/bus_at386.h
+++ b/sys/i386/include/bus_at386.h
@@ -1153,6 +1153,29 @@ bus_space_barrier(bus_space_tag_t tag, bus_space_handle_t bsh,
 }
 	
 
+/*
+ * Generic memory barrier functions.
+ */
+static __inline void
+barrier_read(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0, BUS_SPACE_BARRIER_READ);
+}
+
+static __inline void
+barrier_write(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_WRITE);
+}
+
+static __inline void
+barrier_rw(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_READ | BUS_SPACE_BARRIER_WRITE);
+}
+
 /*
  * Flags used in various bus DMA methods.
  */
diff --git a/sys/i386/include/bus_dma.h b/sys/i386/include/bus_dma.h
index 2d84400e8bd..3423e6b1ad4 100644
--- a/sys/i386/include/bus_dma.h
+++ b/sys/i386/include/bus_dma.h
@@ -1153,6 +1153,29 @@ bus_space_barrier(bus_space_tag_t tag, bus_space_handle_t bsh,
 }
 	
 
+/*
+ * Generic memory barrier functions.
+ */
+static __inline void
+barrier_read(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0, BUS_SPACE_BARRIER_READ);
+}
+
+static __inline void
+barrier_write(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_WRITE);
+}
+
+static __inline void
+barrier_rw(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_READ | BUS_SPACE_BARRIER_WRITE);
+}
+
 /*
  * Flags used in various bus DMA methods.
  */
diff --git a/sys/i386/include/bus_pc98.h b/sys/i386/include/bus_pc98.h
index c18029d791b..fef8b865f59 100644
--- a/sys/i386/include/bus_pc98.h
+++ b/sys/i386/include/bus_pc98.h
@@ -1455,6 +1455,29 @@ bus_space_barrier(bus_space_tag_t tag, bus_space_handle_t bsh,
 }
 	
 
+/*
+ * Generic memory barrier functions.
+ */
+static __inline void
+barrier_read(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0, BUS_SPACE_BARRIER_READ);
+}
+
+static __inline void
+barrier_write(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_WRITE);
+}
+
+static __inline void
+barrier_rw(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_READ | BUS_SPACE_BARRIER_WRITE);
+}
+
 /*
  * Flags used in various bus DMA methods.
  */
diff --git a/sys/ia64/include/bus.h b/sys/ia64/include/bus.h
index c05419317a5..9bb2f76ad78 100644
--- a/sys/ia64/include/bus.h
+++ b/sys/ia64/include/bus.h
@@ -1023,6 +1023,28 @@ bus_space_barrier(bus_space_tag_t tag, bus_space_handle_t bsh,
 	ia64_mf();
 }
 
+/*
+ * Generic memory barrier functions.
+ */
+static __inline void
+barrier_read(void)
+{
+	bus_space_barrier(IA64_BUS_SPACE_MEM, 0, 0, ~0, BUS_SPACE_BARRIER_READ);
+}
+
+static __inline void
+barrier_write(void)
+{
+	bus_space_barrier(IA64_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_WRITE);
+}
+
+static __inline void
+barrier_rw(void)
+{
+	bus_space_barrier(IA64_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_READ | BUS_SPACE_BARRIER_WRITE);
+}
 
 /*
  * Flags used in various bus DMA methods.
diff --git a/sys/sys/bus_dma.h b/sys/sys/bus_dma.h
index 2d84400e8bd..3423e6b1ad4 100644
--- a/sys/sys/bus_dma.h
+++ b/sys/sys/bus_dma.h
@@ -1153,6 +1153,29 @@ bus_space_barrier(bus_space_tag_t tag, bus_space_handle_t bsh,
 }
 	
 
+/*
+ * Generic memory barrier functions.
+ */
+static __inline void
+barrier_read(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0, BUS_SPACE_BARRIER_READ);
+}
+
+static __inline void
+barrier_write(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_WRITE);
+}
+
+static __inline void
+barrier_rw(void)
+{
+	bus_space_barrier(I386_BUS_SPACE_MEM, 0, 0, ~0,
+	    BUS_SPACE_BARRIER_READ | BUS_SPACE_BARRIER_WRITE);
+}
+
 /*
  * Flags used in various bus DMA methods.
  */