1 files changed, 76 insertions, 0 deletions
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index b10ba00cc3e6..4fb06f3e7b3c 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -545,6 +545,82 @@ int __init of_flat_dt_match(unsigned long node, const char *const *compat)
 	return of_fdt_match(initial_boot_params, node, compat);
 }
 
+struct fdt_scan_status {
+	const char *name;
+	int namelen;
+	int depth;
+	int found;
+	int (*iterator)(unsigned long node, const char *uname, int depth, void *data);
+	void *data;
+};
+
+/**
+ * fdt_scan_node_by_path - iterator for of_scan_flat_dt_by_path function
+ */
+static int __init fdt_scan_node_by_path(unsigned long node, const char *uname,
+					int depth, void *data)
+{
+	struct fdt_scan_status *st = data;
+
+	/*
+	 * if scan at the requested fdt node has been completed,
+	 * return -ENXIO to abort further scanning
+	 */
+	if (depth <= st->depth)
+		return -ENXIO;
+
+	/* requested fdt node has been found, so call iterator function */
+	if (st->found)
+		return st->iterator(node, uname, depth, st->data);
+
+	/* check if scanning automata is entering next level of fdt nodes */
+	if (depth == st->depth + 1 &&
+	    strncmp(st->name, uname, st->namelen) == 0 &&
+	    uname[st->namelen] == 0) {
+		st->depth += 1;
+		if (st->name[st->namelen] == 0) {
+			st->found = 1;
+		} else {
+			const char *next = st->name + st->namelen + 1;
+			st->name = next;
+			st->namelen = strcspn(next, "/");
+		}
+		return 0;
+	}
+
+	/* scan next fdt node */
+	return 0;
+}
+
+/**
+ * of_scan_flat_dt_by_path - scan flattened tree blob and call callback on each
+ *			     child of the given path.
+ * @path: path to start searching for children
+ * @it: callback function
+ * @data: context data pointer
+ *
+ * This function is used to scan the flattened device-tree starting from the
+ * node given by path. It is used to extract information (like reserved
+ * memory), which is required on ealy boot before we can unflatten the tree.
+ */
+int __init of_scan_flat_dt_by_path(const char *path,
+	int (*it)(unsigned long node, const char *name, int depth, void *data),
+	void *data)
+{
+	struct fdt_scan_status st = {path, 0, -1, 0, it, data};
+	int ret = 0;
+
+	if (initial_boot_params)
+                ret = of_scan_flat_dt(fdt_scan_node_by_path, &st);
+
+	if (!st.found)
+		return -ENOENT;
+	else if (ret == -ENXIO)	/* scan has been completed */
+		return 0;
+	else
+		return ret;
+}
+
 #ifdef CONFIG_BLK_DEV_INITRD
 /**
  * early_init_dt_check_for_initrd - Decode initrd location from flat tree