libc: Implement ttyname and ttyname_r

Note: this patch can get file path from root pseudo file handle,
but a general infrastructure is setup for other file system too.

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
Change-Id: I86cd79ebb741f2f43fdd398bb7498c40687d949b

fs/inode/fs_inodegetpath.c

@@ -0,0 +1,72 @@
+/****************************************************************************
+ * fs/inode/fs_inodegetpath.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <errno.h>
+#include <string.h>
+#include <nuttx/fs/fs.h>
+
+#include "inode/inode.h"
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: inode_getpath
+ *
+ * Description:
+ *   Given the full path from inode.
+ *
+ ****************************************************************************/
+
+int inode_getpath(FAR struct inode *node, FAR char *path)
+{
+  if (path == NULL)
+    {
+      return -EINVAL;
+    }
+  else if (node == NULL)
+    {
+      path[0] = '\0';
+      return OK;
+    }
+  else if (node->i_parent != NULL)
+    {
+      int ret = inode_getpath(node->i_parent, path);
+      if (ret < 0)
+        {
+          return ret;
+        }
+    }
+
+  strcat(path, node->i_name);
+  if (node->i_child)
+    {
+      strcat(path, "/");
+    }
+
+  return OK;
+}