diff --git a/sys/kern/subr_rman.c b/sys/kern/subr_rman.c
index f5bfd5bc2c70..ce6592ea4d58 100644
--- a/sys/kern/subr_rman.c
+++ b/sys/kern/subr_rman.c
@@ -182,6 +182,16 @@ rman_manage_region(struct rman *rm, u_long start, u_long end)
 	return 0;
 }
 
+int
+rman_init_from_resource(struct rman *rm, struct resource *r)
+{
+	int rv;
+
+	if ((rv = rman_init(rm)) != 0)
+		return (rv);
+	return (rman_manage_region(rm, r->__r_i->r_start, r->__r_i->r_end));
+}
+
 int
 rman_fini(struct rman *rm)
 {
diff --git a/sys/sys/rman.h b/sys/sys/rman.h
index e7831707ec35..ba06cc043cb6 100644
--- a/sys/sys/rman.h
+++ b/sys/sys/rman.h
@@ -35,7 +35,7 @@
 #ifndef	_KERNEL
 #include <sys/queue.h>
 #else
-#include <machine/bus.h>
+#include <machine/_bus.h>
 #include <machine/resource.h>
 #endif
 
@@ -129,6 +129,7 @@ void   *rman_get_virtual(struct resource *);
 int	rman_deactivate_resource(struct resource *r);
 int	rman_fini(struct rman *rm);
 int	rman_init(struct rman *rm);
+int	rman_init_from_resource(struct rman *rm, struct resource *r);
 uint32_t rman_make_alignment_flags(uint32_t size);
 int	rman_manage_region(struct rman *rm, u_long start, u_long end);
 int	rman_is_region_manager(struct resource *r, struct rman *rm);