9.4. Directives¶

This section details the directives of the Clock Manager. A subsection is dedicated to each of this manager’s directives and lists the calling sequence, parameters, description, return values, and notes of the directive.

9.4.1. rtems_clock_set()¶

Sets the CLOCK_REALTIME to the time of day.

CALLING SEQUENCE:

rtems_status_code rtems_clock_set( const rtems_time_of_day *time_of_day );

PARAMETERS:

time_of_day: This parameter is the time of day to set the clock.

RETURN VALUES:

RTEMS_SUCCESSFUL: The requested operation was successful.
RTEMS_INVALID_ADDRESS: The time_of_day parameter was NULL.
RTEMS_INVALID_CLOCK: The time of day specified by time_of_day was invalid.

NOTES:

The date, time, and ticks specified by time_of_day are all range-checked, and an error is returned if any one is out of its valid range.

RTEMS can represent time points of the CLOCK_REALTIME clock in nanoseconds ranging from 1988-01-01T00:00:00.000000000Z to 2514-05-31T01:53:03.999999999Z. The future uptime of the system shall be in this range, otherwise the system behaviour is undefined. Due to implementation constraints, the time of day set by the directive shall be before 2100-01-01:00:00.000000000Z. The latest valid time of day accepted by the POSIX clock_settime() is 2400-01-01T00:00:00.999999999Z.

The specified time is based on the configured clock tick rate, see the CONFIGURE_MICROSECONDS_PER_TICK application configuration option.

Setting the time forward will fire all CLOCK_REALTIME timers which are scheduled at a time point before or at the time set by the directive. This may unblock tasks, which may preempt the calling task. User-provided timer routines will execute in the context of the caller.

It is allowed to call this directive from within interrupt context, however, this is not recommended since an arbitrary number of timers may fire.

The directive shall be called at least once to enable the service of CLOCK_REALTIME related directives. If the clock is not set at least once, they may return an error status.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive may change the priority of a task. This may cause the calling task to be preempted.
The directive may unblock a task. This may cause the calling task to be preempted.
The time of day set by the directive shall be 1988-01-01T00:00:00.000000000Z or later.
The time of day set by the directive shall be before 2100-01-01T00:00:00.000000000Z.

9.4.2. rtems_clock_get_tod()¶

Gets the time of day associated with the current CLOCK_REALTIME.

CALLING SEQUENCE:

rtems_status_code rtems_clock_get_tod( rtems_time_of_day *time_of_day );

PARAMETERS:

time_of_day: This parameter is the pointer to an rtems_time_of_day object. When the directive call is successful, the time of day associated with the CLOCK_REALTIME at some point during the directive call will be stored in this object.

RETURN VALUES:

RTEMS_SUCCESSFUL: The requested operation was successful.
RTEMS_INVALID_ADDRESS: The time_of_day parameter was NULL.
RTEMS_NOT_DEFINED: The CLOCK_REALTIME was not set. It can be set with rtems_clock_set().

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.3. rtems_clock_get_tod_timeval()¶

Gets the seconds and microseconds elapsed since the Unix epoch and the current CLOCK_REALTIME.

CALLING SEQUENCE:

rtems_status_code rtems_clock_get_tod_timeval( struct timeval *time_of_day );

PARAMETERS:

time_of_day: This parameter is the pointer to a struct timeval object. When the directive call is successful, the seconds and microseconds elapsed since the Unix epoch and the CLOCK_REALTIME at some point during the directive call will be stored in this object.

RETURN VALUES:

RTEMS_SUCCESSFUL: The requested operation was successful.
RTEMS_INVALID_ADDRESS: The time_of_day parameter was NULL.
RTEMS_NOT_DEFINED: The CLOCK_REALTIME was not set. It can be set with rtems_clock_set().

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.4. rtems_clock_get_realtime()¶

Gets the time elapsed since the Unix epoch measured using CLOCK_REALTIME in seconds and nanoseconds format.

CALLING SEQUENCE:

void rtems_clock_get_realtime( struct timespec *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct timespec object. The time elapsed since the Unix epoch measured using the CLOCK_REALTIME at some time point during the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive accesses a device provided by the Clock Driver to get the time in the highest resolution available to the system. Alternatively, the rtems_clock_get_realtime_coarse() directive may be used to get the time in a lower resolution and with less runtime overhead.

See rtems_clock_get_realtime_bintime() and rtems_clock_get_realtime_timeval() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.5. rtems_clock_get_realtime_bintime()¶

Gets the time elapsed since the Unix epoch measured using CLOCK_REALTIME in binary time format.

CALLING SEQUENCE:

void rtems_clock_get_realtime_bintime( struct bintime *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct bintime object. The time elapsed since the Unix epoch measured using the CLOCK_REALTIME at some time point during the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive accesses a device provided by the Clock Driver to get the time in the highest resolution available to the system. Alternatively, the rtems_clock_get_realtime_coarse_bintime() directive may be used to get the time in a lower resolution and with less runtime overhead.

See rtems_clock_get_realtime() and rtems_clock_get_realtime_timeval() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.6. rtems_clock_get_realtime_timeval()¶

Gets the time elapsed since the Unix epoch measured using CLOCK_REALTIME in seconds and microseconds format.

CALLING SEQUENCE:

void rtems_clock_get_realtime_timeval( struct timeval *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct timeval object. The time elapsed since the Unix epoch measured using the CLOCK_REALTIME at some time point during the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive accesses a device provided by the Clock Driver to get the time in the highest resolution available to the system. Alternatively, the rtems_clock_get_realtime_coarse_timeval() directive may be used to get the time in a lower resolution and with less runtime overhead.

See rtems_clock_get_realtime() and rtems_clock_get_realtime_bintime() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.7. rtems_clock_get_realtime_coarse()¶

Gets the time elapsed since the Unix epoch measured using CLOCK_REALTIME in coarse resolution in seconds and nanoseconds format.

CALLING SEQUENCE:

void rtems_clock_get_realtime_coarse( struct timespec *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct timespec object. The time elapsed since the Unix epoch measured using the CLOCK_REALTIME at some time point close to the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive does not access a device to get the time. It uses a recent snapshot provided by the Clock Driver. Alternatively, the rtems_clock_get_realtime() directive may be used to get the time in a higher resolution and with a higher runtime overhead.

See rtems_clock_get_realtime_coarse_bintime() and rtems_clock_get_realtime_coarse_timeval() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.8. rtems_clock_get_realtime_coarse_bintime()¶

Gets the time elapsed since the Unix epoch measured using CLOCK_REALTIME in coarse resolution in binary time format.

CALLING SEQUENCE:

void rtems_clock_get_realtime_coarse_bintime( struct bintime *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct bintime object. The time elapsed since the Unix epoch measured using the CLOCK_REALTIME at some time point close to the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive does not access a device to get the time. It uses a recent snapshot provided by the Clock Driver. Alternatively, the rtems_clock_get_realtime_bintime() directive may be used to get the time in a higher resolution and with a higher runtime overhead.

See rtems_clock_get_realtime_coarse() and rtems_clock_get_realtime_coarse_timeval() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.9. rtems_clock_get_realtime_coarse_timeval()¶

Gets the time elapsed since the Unix epoch measured using CLOCK_REALTIME in coarse resolution in seconds and microseconds format.

CALLING SEQUENCE:

void rtems_clock_get_realtime_coarse_timeval( struct timeval *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct timeval object. The time elapsed since the Unix epoch measured using the CLOCK_REALTIME at some time point close to the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive does not access a device to get the time. It uses a recent snapshot provided by the Clock Driver. Alternatively, the rtems_clock_get_realtime_timeval() directive may be used to get the time in a higher resolution and with a higher runtime overhead.

See rtems_clock_get_realtime_coarse() and rtems_clock_get_realtime_coarse_timeval() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.10. rtems_clock_get_monotonic()¶

Gets the time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC in seconds and nanoseconds format.

CALLING SEQUENCE:

void rtems_clock_get_monotonic( struct timespec *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct timespec object. The time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC at some time point during the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive accesses a device provided by the Clock Driver to get the time in the highest resolution available to the system. Alternatively, the rtems_clock_get_monotonic_coarse() directive may be used to get the time with in a lower resolution and with less runtime overhead.

See rtems_clock_get_monotonic_bintime(), rtems_clock_get_monotonic_sbintime(), and rtems_clock_get_monotonic_timeval() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.11. rtems_clock_get_monotonic_bintime()¶

Gets the time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC in binary time format.

CALLING SEQUENCE:

void rtems_clock_get_monotonic_bintime( struct bintime *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct bintime object. The time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC at some time point during the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive accesses a device provided by the Clock Driver to get the time in the highest resolution available to the system. Alternatively, the rtems_clock_get_monotonic_coarse_bintime() directive may be used to get the time in a lower resolution and with less runtime overhead.

See rtems_clock_get_monotonic(), rtems_clock_get_monotonic_sbintime(), and rtems_clock_get_monotonic_timeval() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.12. rtems_clock_get_monotonic_sbintime()¶

Gets the time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC in signed binary time format.

CALLING SEQUENCE:

int64_t rtems_clock_get_monotonic_sbintime( void );

RETURN VALUES:

Returns the time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC at some time point during the directive call.

NOTES:

The directive accesses a device provided by the Clock Driver to get the time in the highest resolution available to the system.

See rtems_clock_get_monotonic(), rtems_clock_get_monotonic_bintime(), and rtems_clock_get_monotonic_timeval() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.13. rtems_clock_get_monotonic_timeval()¶

Gets the time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC in seconds and microseconds format.

CALLING SEQUENCE:

void rtems_clock_get_monotonic_timeval( struct timeval *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct timeval object. The time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC at some time point during the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive accesses a device provided by the Clock Driver to get the time in the highest resolution available to the system. Alternatively, the rtems_clock_get_monotonic_coarse_timeval() directive may be used to get the time in a lower resolution and with less runtime overhead.

See rtems_clock_get_monotonic(), rtems_clock_get_monotonic_bintime(), and rtems_clock_get_monotonic_sbintime() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.14. rtems_clock_get_monotonic_coarse()¶

Gets the time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC in coarse resolution in seconds and nanoseconds format.

CALLING SEQUENCE:

void rtems_clock_get_monotonic_coarse( struct timespec *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct timespec object. The time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC at some time point close to the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive does not access a device to get the time. It uses a recent snapshot provided by the Clock Driver. Alternatively, the rtems_clock_get_monotonic() directive may be used to get the time in a higher resolution and with a higher runtime overhead.

See rtems_clock_get_monotonic_coarse_bintime() and rtems_clock_get_monotonic_coarse_timeval() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.15. rtems_clock_get_monotonic_coarse_bintime()¶

Gets the time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC in coarse resolution in binary time format.

CALLING SEQUENCE:

void rtems_clock_get_monotonic_coarse_bintime( struct bintime *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct bintime object. The time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC at some time point close to the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive does not access a device to get the time. It uses a recent snapshot provided by the Clock Driver. Alternatively, the rtems_clock_get_monotonic_bintime() directive may be used to get the time in a higher resolution and with a higher runtime overhead.

See rtems_clock_get_monotonic_coarse() and rtems_clock_get_monotonic_coarse_timeval() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.16. rtems_clock_get_monotonic_coarse_timeval()¶

Gets the time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC in coarse resolution in seconds and microseconds format.

CALLING SEQUENCE:

void rtems_clock_get_monotonic_coarse_timeval( struct timeval *time_snapshot );

PARAMETERS:

time_snapshot: This parameter is the pointer to a struct timeval object. The time elapsed since some fixed time point in the past measured using the CLOCK_MONOTONIC at some time point close to the directive call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

The directive does not access a device to get the time. It uses a recent snapshot provided by the Clock Driver. Alternatively, the rtems_clock_get_monotonic_timeval() directive may be used to get the time in a higher resolution and with a higher runtime overhead.

See rtems_clock_get_monotonic_coarse() and rtems_clock_get_monotonic_coarse_bintime() to get the time in alternative formats.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.17. rtems_clock_get_boot_time()¶

Gets the time elapsed since the Unix epoch at some time point during system initialization in seconds and nanoseconds format.

CALLING SEQUENCE:

void rtems_clock_get_boot_time( struct timespec *boot_time );

PARAMETERS:

boot_time: This parameter is the pointer to a struct timespec object. The time elapsed since the Unix epoch at some time point during system initialization call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

See rtems_clock_get_boot_time_bintime() and rtems_clock_get_boot_time_timeval() to get the boot time in alternative formats. Setting the CLOCK_REALTIME will also set the boot time.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.18. rtems_clock_get_boot_time_bintime()¶

Gets the time elapsed since the Unix epoch at some time point during system initialization in binary time format.

CALLING SEQUENCE:

void rtems_clock_get_boot_time_bintime( struct bintime *boot_time );

PARAMETERS:

boot_time: This parameter is the pointer to a struct bintime object. The time elapsed since the Unix epoch at some time point during system initialization call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

See rtems_clock_get_boot_time() and rtems_clock_get_boot_time_timeval() to get the boot time in alternative formats. Setting the CLOCK_REALTIME will also set the boot time.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.19. rtems_clock_get_boot_time_timeval()¶

Gets the time elapsed since the Unix epoch at some time point during system initialization in seconds and microseconds format.

CALLING SEQUENCE:

void rtems_clock_get_boot_time_timeval( struct timeval *boot_time );

PARAMETERS:

boot_time: This parameter is the pointer to a struct timeval object. The time elapsed since the Unix epoch at some time point during system initialization call will be stored in this object. Calling the directive with a pointer equal to NULL is undefined behaviour.

NOTES:

See rtems_clock_get_boot_time() and rtems_clock_get_boot_time_bintime() to get the boot time in alternative formats. Setting the CLOCK_REALTIME will also set the boot time.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.20. rtems_clock_get_seconds_since_epoch()¶

Gets the seconds elapsed since the RTEMS epoch and the current CLOCK_REALTIME.

CALLING SEQUENCE:

rtems_status_code rtems_clock_get_seconds_since_epoch(
  rtems_interval *seconds_since_rtems_epoch
);

PARAMETERS:

seconds_since_rtems_epoch: This parameter is the pointer to an rtems_interval object. When the directive call is successful, the seconds elapsed since the RTEMS epoch and the CLOCK_REALTIME at some point during the directive call will be stored in this object.

RETURN VALUES:

RTEMS_SUCCESSFUL: The requested operation was successful.
RTEMS_INVALID_ADDRESS: The seconds_since_rtems_epoch parameter was NULL.
RTEMS_NOT_DEFINED: The CLOCK_REALTIME was not set. It can be set with rtems_clock_set().

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.21. rtems_clock_get_ticks_per_second()¶

Gets the number of clock ticks per second configured for the application.

CALLING SEQUENCE:

rtems_interval rtems_clock_get_ticks_per_second( void );

RETURN VALUES:

Returns the number of clock ticks per second configured for this application.

NOTES:

The number of clock ticks per second is defined indirectly by the CONFIGURE_MICROSECONDS_PER_TICK configuration option.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.

9.4.22. rtems_clock_get_ticks_since_boot()¶

Gets the number of clock ticks since some time point during the system initialization or the last overflow of the clock tick counter.

CALLING SEQUENCE:

rtems_interval rtems_clock_get_ticks_since_boot( void );

RETURN VALUES:

Returns the number of clock ticks since some time point during the system initialization or the last overflow of the clock tick counter.

NOTES:

With a 1ms clock tick, this counter overflows after 50 days since boot. This is the historical measure of uptime in an RTEMS system. The newer service rtems_clock_get_uptime() is another and potentially more accurate way of obtaining similar information.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.

9.4.23. rtems_clock_get_uptime()¶

Gets the seconds and nanoseconds elapsed since some time point during the system initialization using CLOCK_MONOTONIC.

CALLING SEQUENCE:

rtems_status_code rtems_clock_get_uptime( struct timespec *uptime );

PARAMETERS:

uptime: This parameter is the pointer to a struct timespec object. When the directive call is successful, the seconds and nanoseconds elapsed since some time point during the system initialization and some point during the directive call using CLOCK_MONOTONIC will be stored in this object.

RETURN VALUES:

RTEMS_SUCCESSFUL: The requested operation was successful.
RTEMS_INVALID_ADDRESS: The uptime parameter was NULL.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.24. rtems_clock_get_uptime_timeval()¶

Gets the seconds and microseconds elapsed since some time point during the system initialization using CLOCK_MONOTONIC.

CALLING SEQUENCE:

void rtems_clock_get_uptime_timeval( struct timeval *uptime );

PARAMETERS:

uptime: This parameter is the pointer to a struct timeval object. The seconds and microseconds elapsed since some time point during the system initialization and some point during the directive call using CLOCK_MONOTONIC will be stored in this object. The pointer shall be valid, otherwise the behaviour is undefined.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.25. rtems_clock_get_uptime_seconds()¶

Gets the seconds elapsed since some time point during the system initialization using CLOCK_MONOTONIC.

CALLING SEQUENCE:

time_t rtems_clock_get_uptime_seconds( void );

RETURN VALUES:

Returns the seconds elapsed since some time point during the system initialization and some point during the directive call using CLOCK_MONOTONIC.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.26. rtems_clock_get_uptime_nanoseconds()¶

Gets the nanoseconds elapsed since some time point during the system initialization using CLOCK_MONOTONIC.

CALLING SEQUENCE:

uint64_t rtems_clock_get_uptime_nanoseconds( void );

RETURN VALUES:

Returns the nanoseconds elapsed since some time point during the system initialization and some point during the directive call using CLOCK_MONOTONIC.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.27. rtems_clock_tick_later()¶

Gets a clock tick value which is at least delta clock ticks in the future.

CALLING SEQUENCE:

rtems_interval rtems_clock_tick_later( rtems_interval delta );

PARAMETERS:

delta: This parameter is the delta value in clock ticks.

RETURN VALUES:

Returns a clock tick counter value which is at least delta clock ticks in the future.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.28. rtems_clock_tick_later_usec()¶

Gets a clock tick value which is at least delta microseconds in the future.

CALLING SEQUENCE:

rtems_interval rtems_clock_tick_later_usec( rtems_interval delta_in_usec );

PARAMETERS:

delta_in_usec: This parameter is the delta value in microseconds.

RETURN VALUES:

Returns a clock tick counter value which is at least delta_in_usec microseconds in the future.

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.

9.4.29. rtems_clock_tick_before()¶

Indicates if the current clock tick counter is before the ticks.

CALLING SEQUENCE:

bool rtems_clock_tick_before( rtems_interval ticks );

PARAMETERS:

ticks: This parameter is the ticks value to check.

RETURN VALUES:

Returns true, if current clock tick counter indicates a time before the time in ticks, otherwise returns false.

NOTES:

This directive can be used to write busy loops with a timeout.

status busy( void )
{
  rtems_interval timeout;

  timeout = rtems_clock_tick_later_usec( 10000 );

  do {
    if ( ok() ) {
      return success;
    }
  } while ( rtems_clock_tick_before( timeout ) );

  return timeout;
}

CONSTRAINTS:

The following constraints apply to this directive:

The directive may be called from within any runtime context.
The directive will not cause the calling task to be preempted.
The directive requires a Clock Driver.