diff --git a/tools/bus_space/C/lang.c b/tools/bus_space/C/lang.c
index f9b404b1b26c..3ef454466f9d 100644
--- a/tools/bus_space/C/lang.c
+++ b/tools/bus_space/C/lang.c
@@ -227,8 +227,15 @@ busdma_seg_get_size(busdma_seg_t seg)
 }
 
 int
-busdma_sync(busdma_md_t md, int op, bus_addr_t base, bus_size_t size)
+busdma_sync(busdma_md_t md, int op)
 {
 
-	return (bd_sync(md, op, base, size));
+	return (bd_sync(md, op, 0UL, ~0UL));
+}
+
+int
+busdma_sync_range(busdma_md_t md, int op, bus_size_t ofs, bus_size_t len)
+{
+
+	return (bd_sync(md, op, ofs, len));
 }
diff --git a/tools/bus_space/C/libbus.h b/tools/bus_space/C/libbus.h
index 0fae9879d2ce..1f0c3f176516 100644
--- a/tools/bus_space/C/libbus.h
+++ b/tools/bus_space/C/libbus.h
@@ -78,6 +78,7 @@ bus_size_t	busdma_seg_get_size(busdma_seg_t seg);
 #define	BUSDMA_SYNC_PREWRITE    4
 #define	BUSDMA_SYNC_POSTWRITE   8
 
-int	busdma_sync(busdma_md_t md, int op, bus_addr_t, bus_size_t);
+int	busdma_sync(busdma_md_t md, int op);
+int	busdma_sync_range(busdma_md_t md, int op, bus_size_t, bus_size_t);
 
 #endif /* _LIBBUS_SPACE_H_ */
diff --git a/tools/bus_space/Python/lang.c b/tools/bus_space/Python/lang.c
index 48a112ba0c30..0fde8fc1bb62 100644
--- a/tools/bus_space/Python/lang.c
+++ b/tools/bus_space/Python/lang.c
@@ -384,12 +384,27 @@ busdma_seg_get_size(PyObject *self, PyObject *args)
 static PyObject *
 busdma_sync(PyObject *self, PyObject *args)
 {
-	u_long base, size;
 	int error, mdid, op;
 
-	if (!PyArg_ParseTuple(args, "iikk", &mdid, &op, &base, &size))
+	if (!PyArg_ParseTuple(args, "ii", &mdid, &op))
 		return (NULL);
-	error = bd_sync(mdid, op, base, size);
+	error = bd_sync(mdid, op, 0UL, ~0UL);
+	if (error) {
+		PyErr_SetString(PyExc_IOError, strerror(error));
+		return (NULL);
+	}
+	Py_RETURN_NONE;
+}
+
+static PyObject *
+busdma_sync_range(PyObject *self, PyObject *args)
+{
+	u_long ofs, len;
+	int error, mdid, op;
+
+	if (!PyArg_ParseTuple(args, "iikk", &mdid, &op, &ofs, &len))
+		return (NULL);
+	error = bd_sync(mdid, op, ofs, len);
 	if (error) {
 		PyErr_SetString(PyExc_IOError, strerror(error));
 		return (NULL);
@@ -448,7 +463,9 @@ static PyMethodDef busdma_methods[] = {
 	"Return the size of the segment." },
 
     { "sync", busdma_sync, METH_VARARGS,
-	"Keep memory/caches coherent WRT to DMA." },
+	"Make the entire memory descriptor coherent WRT to DMA." },
+    { "sync_range", busdma_sync_range, METH_VARARGS,
+	"Make part of the memory descriptor coherent WRT to DMA." },
 
     { NULL, NULL, 0, NULL }
 };
diff --git a/tools/bus_space/busdma.c b/tools/bus_space/busdma.c
index 3f948b72f983..04a9da8b2ef4 100644
--- a/tools/bus_space/busdma.c
+++ b/tools/bus_space/busdma.c
@@ -536,7 +536,7 @@ bd_seg_get_size(int sid, u_long *size_p)
 }
 
 int
-bd_sync(int mdid, u_int op, u_long base, u_long size)
+bd_sync(int mdid, u_int op, u_long ofs, u_long len)
 {
 	struct proto_ioc_busdma ioc;
 	struct obj *md;
@@ -549,8 +549,8 @@ bd_sync(int mdid, u_int op, u_long base, u_long size)
 	ioc.request = PROTO_IOC_BUSDMA_SYNC;
 	ioc.key = md->key;
 	ioc.u.sync.op = op;
-	ioc.u.sync.base = base;
-	ioc.u.sync.size = size;
+	ioc.u.sync.base = ofs;
+	ioc.u.sync.size = len;
 	if (ioctl(md->fd, PROTO_IOC_BUSDMA, &ioc) == -1)
 		return (errno);
 
diff --git a/tools/bus_space/busdma.h b/tools/bus_space/busdma.h
index cf9d4f27542f..ec4890dd201f 100644
--- a/tools/bus_space/busdma.h
+++ b/tools/bus_space/busdma.h
@@ -51,6 +51,6 @@ int	bd_md_next_seg(int mdid, int sid);
 int	bd_seg_get_addr(int sid, u_long *);
 int	bd_seg_get_size(int sid, u_long *);
 
-int	bd_sync(int mdid, u_int op, u_long base, u_long size);
+int	bd_sync(int mdid, u_int op, u_long ofs, u_long len);
 
 #endif /* _TOOLS_BUS_DMA_H_ */