Index: uspace/srv/devman/devman.c
===================================================================
--- uspace/srv/devman/devman.c	(revision 4265fd4cfd339bb9dddcf6a99fd97a78197407e7)
+++ uspace/srv/devman/devman.c	(revision 0876062b1bae2fe8bf001411631addd301e0647d)
@@ -1165,4 +1165,33 @@
 }
 
+/** Find function with a specified name belonging to given device.
+ *
+ * Device tree rwlock should be held at least for reading.
+ *
+ * @param dev Device the function belongs to.
+ * @param name Function name (not path).
+ * @return Function node.
+ * @retval NULL No function with given name.
+ */
+fun_node_t *find_fun_node_in_device(dev_node_t *dev, const char *name)
+{
+	assert(dev != NULL);
+	assert(name != NULL);
+
+	fun_node_t *fun;
+	link_t *link;
+
+	for (link = dev->functions.next;
+	    link != &dev->functions;
+	    link = link->next) {
+		fun = list_get_instance(link, fun_node_t, dev_functions);
+
+		if (str_cmp(name, fun->name) == 0)
+			return fun;
+	}
+
+	return NULL;
+}
+
 /** Find child function node with a specified name.
  *
@@ -1175,19 +1204,5 @@
 fun_node_t *find_node_child(fun_node_t *pfun, const char *name)
 {
-	fun_node_t *fun;
-	link_t *link;
-	
-	link = pfun->child->functions.next;
-	
-	while (link != &pfun->child->functions) {
-		fun = list_get_instance(link, fun_node_t, dev_functions);
-		
-		if (str_cmp(name, fun->name) == 0)
-			return fun;
-		
-		link = link->next;
-	}
-	
-	return NULL;
+	return find_fun_node_in_device(pfun->child, name);
 }
 
Index: uspace/srv/devman/devman.h
===================================================================
--- uspace/srv/devman/devman.h	(revision 4265fd4cfd339bb9dddcf6a99fd97a78197407e7)
+++ uspace/srv/devman/devman.h	(revision 0876062b1bae2fe8bf001411631addd301e0647d)
@@ -338,4 +338,5 @@
 extern fun_node_t *find_fun_node(dev_tree_t *tree, devman_handle_t handle);
 extern fun_node_t *find_fun_node_by_path(dev_tree_t *, char *);
+extern fun_node_t *find_fun_node_in_device(dev_node_t *, const char *);
 
 /* Device tree */
Index: uspace/srv/devman/main.c
===================================================================
--- uspace/srv/devman/main.c	(revision 4265fd4cfd339bb9dddcf6a99fd97a78197407e7)
+++ uspace/srv/devman/main.c	(revision 0876062b1bae2fe8bf001411631addd301e0647d)
@@ -243,4 +243,14 @@
 	}
 	
+	/* Check that function with same name is not there already. */
+	if (find_fun_node_in_device(pdev, fun_name) != NULL) {
+		fibril_rwlock_write_unlock(&tree->rwlock);
+		async_answer_0(callid, EEXISTS);
+		printf(NAME ": Warning, driver tried to register `%s' twice.\n",
+		    fun_name);
+		free(fun_name);
+		return;
+	}
+
 	fun_node_t *fun = create_fun_node();
 	if (!insert_fun_node(&device_tree, fun, fun_name, pdev)) {