of: introduce of_parse_phandle_with_fixed_args

This is identical to of_parse_phandle_with_args(), except that the
number of argument cells is fixed, rather than being parsed out of the
node referenced by each phandle.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Grant Likely <grant.likely@linaro.org>

drivers/of/base.c

@@ -1082,7 +1082,8 @@ EXPORT_SYMBOL_GPL(of_property_count_strings);
 
 static int __of_parse_phandle_with_args(const struct device_node *np,
 					const char *list_name,
-					const char *cells_name, int index,
+					const char *cells_name,
+					int cell_count, int index,
 					struct of_phandle_args *out_args)
 {
 	const __be32 *list, *list_end;
@@ -1118,12 +1119,18 @@ static int __of_parse_phandle_with_args(const struct device_node *np,
 					 np->full_name);
 				goto err;
 			}
-			if (of_property_read_u32(node, cells_name, &count)) {
+
+			if (cells_name) {
+				if (of_property_read_u32(node, cells_name,
+							 &count)) {
 					pr_err("%s: could not get %s for %s\n",
 						np->full_name, cells_name,
 						node->full_name);
 					goto err;
 				}
+			} else {
+				count = cell_count;
+			}
 
 			/*
 			 * Make sure that the arguments actually fit in the
@@ -1244,10 +1251,52 @@ int of_parse_phandle_with_args(const struct device_node *np, const char *list_na
 {
 	if (index < 0)
 		return -EINVAL;
-	return __of_parse_phandle_with_args(np, list_name, cells_name, index, out_args);
+	return __of_parse_phandle_with_args(np, list_name, cells_name, 0,
+					    index, out_args);
 }
 EXPORT_SYMBOL(of_parse_phandle_with_args);
 
+/**
+ * of_parse_phandle_with_fixed_args() - Find a node pointed by phandle in a list
+ * @np:		pointer to a device tree node containing a list
+ * @list_name:	property name that contains a list
+ * @cell_count: number of argument cells following the phandle
+ * @index:	index of a phandle to parse out
+ * @out_args:	optional pointer to output arguments structure (will be filled)
+ *
+ * This function is useful to parse lists of phandles and their arguments.
+ * Returns 0 on success and fills out_args, on error returns appropriate
+ * errno value.
+ *
+ * Caller is responsible to call of_node_put() on the returned out_args->node
+ * pointer.
+ *
+ * Example:
+ *
+ * phandle1: node1 {
+ * }
+ *
+ * phandle2: node2 {
+ * }
+ *
+ * node3 {
+ * 	list = <&phandle1 0 2 &phandle2 2 3>;
+ * }
+ *
+ * To get a device_node of the `node2' node you may call this:
+ * of_parse_phandle_with_fixed_args(node3, "list", 2, 1, &args);
+ */
+int of_parse_phandle_with_fixed_args(const struct device_node *np,
+				const char *list_name, int cell_count,
+				int index, struct of_phandle_args *out_args)
+{
+	if (index < 0)
+		return -EINVAL;
+	return __of_parse_phandle_with_args(np, list_name, NULL, cell_count,
+					   index, out_args);
+}
+EXPORT_SYMBOL(of_parse_phandle_with_fixed_args);
+
 /**
  * of_count_phandle_with_args() - Find the number of phandles references in a property
  * @np:		pointer to a device tree node containing a list
@@ -1266,7 +1315,8 @@ EXPORT_SYMBOL(of_parse_phandle_with_args);
 int of_count_phandle_with_args(const struct device_node *np, const char *list_name,
 				const char *cells_name)
 {
-	return __of_parse_phandle_with_args(np, list_name, cells_name, -1, NULL);
+	return __of_parse_phandle_with_args(np, list_name, cells_name, 0, -1,
+					    NULL);
 }
 EXPORT_SYMBOL(of_count_phandle_with_args);
 

include/linux/of.h

@@ -280,6 +280,9 @@ extern struct device_node *of_parse_phandle(const struct device_node *np,
 extern int of_parse_phandle_with_args(const struct device_node *np,
 	const char *list_name, const char *cells_name, int index,
 	struct of_phandle_args *out_args);
+extern int of_parse_phandle_with_fixed_args(const struct device_node *np,
+	const char *list_name, int cells_count, int index,
+	struct of_phandle_args *out_args);
 extern int of_count_phandle_with_args(const struct device_node *np,
 	const char *list_name, const char *cells_name);
 
@@ -477,6 +480,13 @@ static inline int of_parse_phandle_with_args(struct device_node *np,
 	return -ENOSYS;
 }
 
+static inline int of_parse_phandle_with_fixed_args(const struct device_node *np,
+	const char *list_name, int cells_count, int index,
+	struct of_phandle_args *out_args)
+{
+	return -ENOSYS;
+}
+
 static inline int of_count_phandle_with_args(struct device_node *np,
 					     const char *list_name,
 					     const char *cells_name)