fs/vfs: Add file descriptor based timers support

Signed-off-by: Petro Karashchenko <petro.karashchenko@gmail.com>

include/nuttx/wdog.h

@@ -90,7 +90,7 @@ extern "C"
  * Name: wd_start
  *
  * Description:
- *   This function adds a watchdog timer to the actuve timer queue.  The
+ *   This function adds a watchdog timer to the active timer queue.  The
  *   specified watchdog function at 'wdentry' will be called from the
  *   interrupt level after the specified number of ticks has elapsed.
  *   Watchdog timers may be started from the interrupt level.

include/sys/syscall_lookup.h

@@ -218,6 +218,11 @@ SYSCALL_LOOKUP(pwrite,                     4)
 #ifdef CONFIG_EVENT_FD
   SYSCALL_LOOKUP(eventfd,                  2)
 #endif
+#ifdef CONFIG_TIMER_FD
+  SYSCALL_LOOKUP(timerfd_create,           2)
+  SYSCALL_LOOKUP(timerfd_settime,          4)
+  SYSCALL_LOOKUP(timerfd_gettime,          2)
+#endif
 #ifdef CONFIG_SERIAL_TERMIOS
   SYSCALL_LOOKUP(tcdrain,                  1)
 #endif

include/sys/timerfd.h

@@ -0,0 +1,80 @@
+/****************************************************************************
+ * include/sys/timerfd.h
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_SYS_TIMERFD_H
+#define __INCLUDE_SYS_TIMERFD_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <stdint.h>
+#include <fcntl.h>
+#include <time.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define TFD_NONBLOCK O_NONBLOCK
+#define TFD_CLOEXEC  O_CLOEXEC
+
+#define TFD_TIMER_ABSTIME TIMER_ABSTIME
+
+/****************************************************************************
+ * Public Type Declarations
+ ****************************************************************************/
+
+/* Type for timer counter */
+
+/* Type for event counter */
+
+#ifdef __INT64_DEFINED
+typedef uint64_t timerfd_t;
+#else
+typedef uint32_t timerfd_t;
+#endif
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+#ifdef __cplusplus
+#define EXTERN extern "C"
+extern "C"
+{
+#else
+#define EXTERN extern
+#endif
+
+int timerfd_create(int clockid, int flags);
+
+int timerfd_settime(int fd, int flags,
+                    FAR const struct itimerspec *new_value,
+                    FAR struct itimerspec *old_value);
+
+int timerfd_gettime(int fd, FAR struct itimerspec *curr_value);
+
+#undef EXTERN
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __INCLUDE_SYS_TIMERFD_H */