serial: Move tcdrain implementation from drivers/serial to libc

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

libs/libc/termios/Make.defs

@@ -26,7 +26,7 @@ ifeq ($(CONFIG_SERIAL_TERMIOS),y)
 # Add the termios C files to the build
 
 CSRCS += lib_cfspeed.c lib_cfmakeraw.c lib_isatty.c lib_tcflush.c
-CSRCS += lib_tcflow.c lib_tcgetattr.c lib_tcsetattr.c
+CSRCS += lib_tcdrain.c lib_tcflow.c lib_tcgetattr.c lib_tcsetattr.c
 CSRCS += lib_ttyname.c lib_ttynamer.c
 
 # Add the termios directory to the build

libs/libc/termios/lib_tcdrain.c

@@ -0,0 +1,57 @@
+/****************************************************************************
+ * libs/libc/termios/lib_tcdrain.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 <sys/ioctl.h>
+
+#include <termios.h>
+#include <errno.h>
+
+#include <nuttx/serial/tioctl.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: tcdrain
+ *
+ * Description:
+ *   Function for draining the output buffer of a terminal/serial device
+ *
+ * Input Parameters:
+ *   fd  - The 'fd' argument is an open file descriptor associated with a
+ *         terminal.
+ *
+ * Returned Value:
+ *   Upon successful completion, 0 is returned. Otherwise, -1 is returned and
+ *   errno is set to indicate the error.
+ *
+ ****************************************************************************/
+
+int tcdrain(int fd)
+{
+  return ioctl(fd, TCDRN, (unsigned long)0);
+}