1 files changed, 109 insertions, 0 deletions

diff --git a/drivers/of/base.c b/drivers/of/base.c
index cd1ce7ab8517..4270eb4a26a1 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -458,3 +458,112 @@ int of_modalias_node(struct device_node *node, char *modalias, int len)
 }
 EXPORT_SYMBOL_GPL(of_modalias_node);
 
+/**
+ * of_parse_phandles_with_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
+ * @cells_name: property name that specifies phandles' arguments count
+ * @index:      index of a phandle to parse out
+ * @out_node:   pointer to device_node struct pointer (will be filled)
+ * @out_args:   pointer to arguments pointer (will be filled)
+ *
+ * This function is useful to parse lists of phandles and their arguments.
+ * Returns 0 on success and fills out_node and out_args, on error returns
+ * appropriate errno value.
+ *
+ * Example:
+ *
+ * phandle1: node1 {
+ *      #list-cells = <2>;
+ * }
+ *
+ * phandle2: node2 {
+ *      #list-cells = <1>;
+ * }
+ *
+ * node3 {
+ *      list = <&phandle1 1 2 &phandle2 3>;
+ * }
+ *
+ * To get a device_node of the `node2' node you may call this:
+ * of_parse_phandles_with_args(node3, "list", "#list-cells", 2, &node2, &args);
+ */
+int of_parse_phandles_with_args(struct device_node *np, const char *list_name,
+                                const char *cells_name, int index,
+                                struct device_node **out_node,
+                                const void **out_args)
+{
+        int ret = -EINVAL;
+        const u32 *list;
+        const u32 *list_end;
+        int size;
+        int cur_index = 0;
+        struct device_node *node = NULL;
+        const void *args;
+
+        list = of_get_property(np, list_name, &size);
+        if (!list) {
+                ret = -ENOENT;
+                goto err0;
+        }
+        list_end = list + size / sizeof(*list);
+
+        while (list < list_end) {
+                const u32 *cells;
+                const phandle *phandle;
+
+                phandle = list;
+                args = list + 1;
+
+                /* one cell hole in the list = <>; */
+                if (!*phandle) {
+                        list++;
+                        goto next;
+                }
+
+                node = of_find_node_by_phandle(*phandle);
+                if (!node) {
+                        pr_debug("%s: could not find phandle\n",
+                                 np->full_name);
+                        goto err0;
+                }
+
+                cells = of_get_property(node, cells_name, &size);
+                if (!cells || size != sizeof(*cells)) {
+                        pr_debug("%s: could not get %s for %s\n",
+                                 np->full_name, cells_name, node->full_name);
+                        goto err1;
+                }
+
+                /* Next phandle is at offset of one phandle cell + #cells */
+                list += 1 + *cells;
+                if (list > list_end) {
+                        pr_debug("%s: insufficient arguments length\n",
+                                 np->full_name);
+                        goto err1;
+                }
+next:
+                if (cur_index == index)
+                        break;
+
+                of_node_put(node);
+                node = NULL;
+                cur_index++;
+        }
+
+        if (!node) {
+                ret = -ENOENT;
+                goto err0;
+        }
+
+        *out_node = node;
+        *out_args = args;
+
+        return 0;
+err1:
+        of_node_put(node);
+err0:
+        pr_debug("%s failed with status %d\n", __func__, ret);
+        return ret;
+}
+EXPORT_SYMBOL(of_parse_phandles_with_args);