fdt: Add a function to count strings

Given a device tree node and a property name, the fdt_count_strings()
function counts the number of strings found in the property value.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>

include/libfdt.h

@@ -857,6 +857,15 @@ int fdt_node_offset_by_compatible(const void *fdt, int startoffset,
  */
 int fdt_stringlist_contains(const char *strlist, int listlen, const char *str);
 
+/**
+ * fdt_count_strings - count the number of strings in a string list
+ * @fdt: pointer to the device tree blob
+ * @node: offset of the node
+ * @property: name of the property containing the string list
+ * @return: the number of strings in the given property
+ */
+int fdt_count_strings(const void *fdt, int node, const char *property);
+
 /**********************************************************************/
 /* Read-only functions (addressing related)                           */
 /**********************************************************************/

lib/libfdt/fdt_ro.c

@@ -491,6 +491,26 @@ int fdt_stringlist_contains(const char *strlist, int listlen, const char *str)
 	return 0;
 }
 
+int fdt_count_strings(const void *fdt, int node, const char *property)
+{
+	int length, i, count = 0;
+	const char *list;
+
+	list = fdt_getprop(fdt, node, property, &length);
+	if (!list)
+		return -length;
+
+	for (i = 0; i < length; i++) {
+		int len = strlen(list);
+
+		list += len + 1;
+		i += len;
+		count++;
+	}
+
+	return count;
+}
+
 int fdt_node_check_compatible(const void *fdt, int nodeoffset,
 			      const char *compatible)
 {