[Qemu-devel] [PATCH v2 3/7] device_tree: introduce qemu_fdt_node_path

[Eric Auger]

This new helper routine returns the node path of a device
referred to by its node name and compat string.

Signed-off-by: Eric Auger <address@hidden>

---

v1 -> v2:
- move doc comment in header file
- do not use a fixed size buffer
- break on errors in while loop
- use strcmp instead of strncmp

RFC -> v1:
- improve error handling according to Alex' comments
---
 device_tree.c                | 37 +++++++++++++++++++++++++++++++++++++
 include/sysemu/device_tree.h | 14 ++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/device_tree.c b/device_tree.c
index b262c2d..8441e01 100644
--- a/device_tree.c
+++ b/device_tree.c
@@ -231,6 +231,43 @@ static int findnode_nofail(void *fdt, const char 
*node_path)
     return offset;
 }
 
+int qemu_fdt_node_path(void *fdt, const char *name, char *compat,
+                       char **node_path)
+{
+    int offset, len, ret;
+    const char *iter_name;
+    unsigned int path_len = 16;
+    char *path;
+
+    *node_path = NULL;
+    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)) {
+            goto found;
+        }
+        offset = fdt_node_offset_by_compatible(fdt, offset, compat);
+    }
+    return offset;
+
+found:
+    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);
+    }
+    if (!ret) {
+        *node_path = path;
+    }
+    return ret;
+}
+
 int qemu_fdt_setprop(void *fdt, const char *node_path,
                      const char *property, const void *val, int size)
 {
diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
index fdf25a4..269cb1c 100644
--- a/include/sysemu/device_tree.h
+++ b/include/sysemu/device_tree.h
@@ -20,6 +20,20 @@ void *load_device_tree(const char *filename_path, int 
*sizep);
 void *load_device_tree_from_sysfs(void);
 #endif
 
+/**
+ * qemu_fdt_node_path: return the node path of a device, given its
+ * node name and its compat string
+ * @fdt: pointer to the dt blob
+ * @name: device node name
+ * @compat: compatibility string of the device
+ * @node_path: returned node path
+ *
+ * upon success, the path is output at node_path address
+ * returns 0 on success, < 0 on failure
+ */
+int qemu_fdt_node_path(void *fdt, const char *name, char *compat,
+                       char **node_path);
+
 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,
-- 
1.9.1