sched/hrtimer: Add hrtimer_gettime.

This commit added hrtimer_gettime API to support the query of the
rest of the delay time of the hrtimer in nanoseconds.

Signed-off-by: ouyangxiangzhen <ouyangxiangzhen@xiaomi.com>

include/nuttx/hrtimer.h

@@ -199,6 +199,25 @@ int hrtimer_start(FAR hrtimer_t *hrtimer, hrtimer_entry_t func,
                   uint64_t expired,
                   enum hrtimer_mode_e mode);
 
+/****************************************************************************
+ * Name: hrtimer_gettime
+ *
+ * Description:
+ *   Get the rest of the delay time of the hrtimer in nanoseconds.
+ *
+ * Input Parameters:
+ *   timer - The hrtimer to be queried.
+ *
+ * Returned Value
+ *   The time until next expiration in nanoseconds.
+ *
+ * Assumption:
+ *   The timer should not be NULL.
+ *
+ ****************************************************************************/
+
+uint64_t hrtimer_gettime(FAR hrtimer_t *timer);
+
 #undef EXTERN
 #ifdef __cplusplus
 }

sched/hrtimer/CMakeLists.txt

@@ -23,8 +23,14 @@
 # Add hrtimer-related files to the build
 set(CSRCS)
 if(CONFIG_HRTIMER)
-  list(APPEND CSRCS hrtimer_cancel.c hrtimer_initialize.c hrtimer_process.c
+  list(
-       hrtimer_start.c)
+    APPEND
+    CSRCS
+    hrtimer_cancel.c
+    hrtimer_initialize.c
+    hrtimer_process.c
+    hrtimer_start.c
+    hrtimer_gettime.c)
 endif()
 
 target_sources(sched PRIVATE ${CSRCS})

sched/hrtimer/Make.defs

@@ -24,6 +24,7 @@
 
 ifeq ($(CONFIG_HRTIMER),y)
   CSRCS += hrtimer_cancel.c hrtimer_initialize.c hrtimer_process.c hrtimer_start.c
+  CSRCS += hrtimer_gettime.c
 endif
 
 # Include hrtimer build support

sched/hrtimer/hrtimer_gettime.c

@@ -0,0 +1,58 @@
+/****************************************************************************
+ * sched/hrtimer/hrtimer_gettime.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * 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 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 "hrtimer/hrtimer.h"
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: hrtimer_gettime
+ *
+ * Description:
+ *   Get the rest of the delay time of the hrtimer in nanoseconds.
+ *
+ * Input Parameters:
+ *   timer - The hrtimer to be queried.
+ *
+ * Returned Value
+ *   The time until next expiration in nanoseconds.
+ *
+ * Assumption:
+ *   The timer should not be NULL.
+ *
+ ****************************************************************************/
+
+uint64_t hrtimer_gettime(FAR hrtimer_t *timer)
+{
+  uint64_t expire = hrtimer_read_64(&timer->expired);
+  int64_t  remain = expire - clock_systime_nsec();
+
+  return remain < 0 ? 0u : remain;
+}