/****************************************************************************
*
* Copyright (C) 2012 PX4 Development Team. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
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* used to endorse or promote products derived from this software
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*
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****************************************************************************/
/**
* @file drv_hrt.h
*
* High-resolution timer with callouts and timekeeping.
*/
#pragma once
#include <sys/types.h>
#include <stdbool.h>
#include <time.h>
#include <queue.h>
__BEGIN_DECLS
/*
* Absolute time, in microsecond units.
*
* Absolute time is measured from some arbitrary epoch shortly after
* system startup. It should never wrap or go backwards.
*/
typedef uint64_t hrt_abstime;
/*
* Callout function type.
*
* Note that callouts run in the timer interrupt context, so
* they are serialised with respect to each other, and must not
* block.
*/
typedef void (* hrt_callout)(void *arg);
/*
* Callout record.
*/
typedef struct hrt_call {
struct sq_entry_s link;
hrt_abstime deadline;
hrt_abstime period;
hrt_callout callout;
void *arg;
} *hrt_call_t;
/*
* Get absolute time.
*/
__EXPORT extern hrt_abstime hrt_absolute_time(void);
/*
* Convert a timespec to absolute time.
*/
__EXPORT extern hrt_abstime ts_to_abstime(struct timespec *ts);
/*
* Convert absolute time to a timespec.
*/
__EXPORT extern void abstime_to_ts(struct timespec *ts, hrt_abstime abstime);
/*
* Compute the delta between a timestamp taken in the past
* and now.
*
* This function is safe to use even if the timestamp is updated
* by an interrupt during execution.
*/
__EXPORT extern hrt_abstime hrt_elapsed_time(const volatile hrt_abstime *then);
/*
* Store the absolute time in an interrupt-safe fashion.
*
* This function ensures that the timestamp cannot be seen half-written by an interrupt handler.
*/
__EXPORT extern hrt_abstime hrt_store_absolute_time(volatile hrt_abstime *now);
/*
* Call callout(arg) after delay has elapsed.
*
* If callout is NULL, this can be used to implement a timeout by testing the call
* with hrt_called().
*/
__EXPORT extern void hrt_call_after(struct hrt_call *entry, hrt_abstime delay, hrt_callout callout, void *arg);
/*
* Call callout(arg) at absolute time calltime.
*/
__EXPORT extern void hrt_call_at(struct hrt_call *entry, hrt_abstime calltime, hrt_callout callout, void *arg);
/*
* Call callout(arg) after delay, and then after every interval.
*
* Note thet the interval is timed between scheduled, not actual, call times, so the call rate may
* jitter but should not drift.
*/
__EXPORT extern void hrt_call_every(struct hrt_call *entry, hrt_abstime delay, hrt_abstime interval, hrt_callout callout, void *arg);
/*
* If this returns true, the entry has been invoked and removed from the callout list,
* or it has never been entered.
*
* Always returns false for repeating callouts.
*/
__EXPORT extern bool hrt_called(struct hrt_call *entry);
/*
* Remove the entry from the callout list.
*/
__EXPORT extern void hrt_cancel(struct hrt_call *entry);
/*
* Initialise the HRT.
*/
__EXPORT extern void hrt_init(void);
__END_DECLS
