sched/hrtimer/hrtimer_start.c

/****************************************************************************
 * sched/hrtimer/hrtimer_start.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 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 <nuttx/arch.h>
#include <nuttx/clock.h>
#include <errno.h>

#include "hrtimer/hrtimer.h"

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: hrtimer_start_absolute
 *
 * Description:
 *   Start a high-resolution timer to expire after a specified duration
 *   in nanoseconds.
 *
 * Input Parameters:
 *   hrtimer - Pointer to the hrtimer.
 *   func    - Expiration callback function.
 *   expired - Expiration time in nanoseconds.
 *
 * Returned Value:
 *   OK (0) on success, or a negated errno value on failure.
 *
 * Assumptions:
 *   - hrtimer is not NULL and func is not NULL.
 *
 ****************************************************************************/

int hrtimer_start_absolute(FAR hrtimer_t *hrtimer, hrtimer_entry_t func,
                           uint64_t expired)
{
  irqstate_t flags;
  bool       reprogram = false;
  int        ret       = OK;

  DEBUGASSERT(hrtimer != NULL && func != NULL);

  /* Acquire the lock and seize the ownership of the hrtimer queue. */

  flags = write_seqlock_irqsave(&g_hrtimer_lock);

  /* Ensure no running core can write the hrtimer. */

  hrtimer_cancel_running(hrtimer);

  if (hrtimer_is_pending(hrtimer))
    {
      reprogram = hrtimer_remove(hrtimer);
    }

  hrtimer->func    = func;
  hrtimer->expired = expired;

  /* Insert the timer into the hrtimer queue. */

  reprogram |= hrtimer_insert(hrtimer);

  /* If the inserted timer is now the earliest, start hardware timer */

  if (reprogram)
    {
      hrtimer_reprogram(hrtimer->expired);
    }

  /* Release the lock and give up the ownership of the hrtimer queue. */

  write_sequnlock_irqrestore(&g_hrtimer_lock, flags);

  return ret;
}