libfdt: Add fdt_path_offset_namelen

Add a namelen variant of fdt_path_offset to retrieve the node offset using
only a fixed number of characters.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

include/libfdt.h

@@ -365,6 +365,17 @@ int fdt_subnode_offset_namelen(const void *fdt, int parentoffset,
  */
 int fdt_subnode_offset(const void *fdt, int parentoffset, const char *name);
 
+/**
+ * fdt_path_offset_namelen - find a tree node based on substring
+ * @fdt: pointer to the device tree blob
+ * @path: full path of the node to locate
+ * @namelen: number of characters of name to consider
+ *
+ * Identical to fdt_path_offset(), but only examine the first
+ * namelen characters of path for matching the node path.
+ */
+int fdt_path_offset_namelen(const void *fdt, const char *path, int namelen);
+
 /**
  * fdt_path_offset - find a tree node by its full path
  * @fdt: pointer to the device tree blob
@@ -387,7 +398,10 @@ int fdt_subnode_offset(const void *fdt, int parentoffset, const char *name);
  *	-FDT_ERR_BADSTRUCTURE,
  *	-FDT_ERR_TRUNCATED, standard meanings.
  */
-int fdt_path_offset(const void *fdt, const char *path);
+static inline int fdt_path_offset(const void *fdt, const char *path)
+{
+	return fdt_path_offset_namelen(fdt, path, strlen(path));
+}
 
 /**
  * fdt_get_name - retrieve the name of a given node

lib/libfdt/fdt_ro.c

@@ -145,10 +145,10 @@ int fdt_subnode_offset(const void *fdt, int parentoffset,
  * "foo/bar:option" and "bar:option/otheroption", both of which happen, so
  * first searching for either ':' or '/' does not work.
  */
-static const char *fdt_path_next_separator(const char *path)
+static const char *fdt_path_next_separator(const char *path, int len)
 {
-	const char *sep1 = strchr(path, '/');
-	const char *sep2 = strchr(path, ':');
+	const void *sep1 = memchr(path, '/', len);
+	const void *sep2 = memchr(path, ':', len);
 
 	if (sep1 && sep2)
 		return (sep1 < sep2) ? sep1 : sep2;
@@ -158,9 +158,9 @@ static const char *fdt_path_next_separator(const char *path)
 		return sep2;
 }
 
-int fdt_path_offset(const void *fdt, const char *path)
+int fdt_path_offset_namelen(const void *fdt, const char *path, int namelen)
 {
-	const char *end = path + strlen(path);
+	const char *end = path + namelen;
 	const char *p = path;
 	int offset = 0;
 
@@ -168,7 +168,7 @@ int fdt_path_offset(const void *fdt, const char *path)
 
 	/* see if we have an alias */
 	if (*path != '/') {
-		const char *q = fdt_path_next_separator(path);
+		const char *q = fdt_path_next_separator(path, namelen);
 
 		if (!q)
 			q = end;
@@ -181,14 +181,16 @@ int fdt_path_offset(const void *fdt, const char *path)
 		p = q;
 	}
 
-	while (*p) {
+	while (*p && (p < end)) {
 		const char *q;
 
 		while (*p == '/')
 			p++;
+
 		if (*p == '\0' || *p == ':')
 			return offset;
-		q = fdt_path_next_separator(p);
+
+		q = fdt_path_next_separator(p, end - p);
 		if (!q)
 			q = end;