device_tree: introduce qemu_fdt_node_path

This new helper routine returns a NULL terminated array of
node paths matching a node name and a compat string.

Signed-off-by: Eric Auger <eric.auger@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

device_tree.c

@@ -226,6 +226,60 @@ static int findnode_nofail(void *fdt, const char *node_path)
     return offset;
 }
 
+char **qemu_fdt_node_path(void *fdt, const char *name, char *compat,
+                          Error **errp)
+{
+    int offset, len, ret;
+    const char *iter_name;
+    unsigned int path_len = 16, n = 0;
+    GSList *path_list = NULL, *iter;
+    char **path_array;
+
+    offset = fdt_node_offset_by_compatible(fdt, -1, compat);
+
+    while (offset >= 0) {
+        iter_name = fdt_get_name(fdt, offset, &len);
+        if (!iter_name) {
+            offset = len;
+            break;
+        }
+        if (!strcmp(iter_name, name)) {
+            char *path;
+
+            path = g_malloc(path_len);
+            while ((ret = fdt_get_path(fdt, offset, path, path_len))
+                  == -FDT_ERR_NOSPACE) {
+                path_len += 16;
+                path = g_realloc(path, path_len);
+            }
+            path_list = g_slist_prepend(path_list, path);
+            n++;
+        }
+        offset = fdt_node_offset_by_compatible(fdt, offset, compat);
+    }
+
+    if (offset < 0 && offset != -FDT_ERR_NOTFOUND) {
+        error_setg(errp, "%s: abort parsing dt for %s/%s: %s",
+                   __func__, name, compat, fdt_strerror(offset));
+        for (iter = path_list; iter; iter = iter->next) {
+            g_free(iter->data);
+        }
+        g_slist_free(path_list);
+        return NULL;
+    }
+
+    path_array = g_new(char *, n + 1);
+    path_array[n--] = NULL;
+
+    for (iter = path_list; iter; iter = iter->next) {
+        path_array[n--] = iter->data;
+    }
+
+    g_slist_free(path_list);
+
+    return path_array;
+}
+
 int qemu_fdt_setprop(void *fdt, const char *node_path,
                      const char *property, const void *val, int size)
 {

include/sysemu/device_tree.h

@@ -25,6 +25,24 @@ void *load_device_tree(const char *filename_path, int *sizep);
 void *load_device_tree_from_sysfs(void);
 #endif
 
+/**
+ * qemu_fdt_node_path: return the paths of nodes matching a given
+ * name and compat string
+ * @fdt: pointer to the dt blob
+ * @name: node name
+ * @compat: compatibility string
+ * @errp: handle to an error object
+ *
+ * returns a newly allocated NULL-terminated array of node paths.
+ * Use g_strfreev() to free it. If one or more nodes were found, the
+ * array contains the path of each node and the last element equals to
+ * NULL. If there is no error but no matching node was found, the
+ * returned array contains a single element equal to NULL. If an error
+ * was encountered when parsing the blob, the function returns NULL
+ */
+char **qemu_fdt_node_path(void *fdt, const char *name, char *compat,
+                          Error **errp);
+
 int qemu_fdt_setprop(void *fdt, const char *node_path,
                      const char *property, const void *val, int size);
 int qemu_fdt_setprop_cell(void *fdt, const char *node_path,