/**
* @file rtems/rtems/event.h
*
* This include file contains the information pertaining to the Event
* Manager. This manager provides a high performance method of communication
* and synchronization.
*
* Directives provided are:
*
* - send an event set to a task
* - receive event condition
*
*/
/* COPYRIGHT (c) 1989-2008.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*
* $Id$
*/
#ifndef _RTEMS_RTEMS_EVENT_H
#define _RTEMS_RTEMS_EVENT_H
/**
* This constant is defined to extern most of the time when using
* this header file. However by defining it to nothing, the data
* declared in this header file can be instantiated. This is done
* in a single per manager file.
*/
#ifndef RTEMS_EVENT_EXTERN
#define RTEMS_EVENT_EXTERN extern
#endif
#ifdef __cplusplus
extern "C" {
#endif
#include <rtems/score/object.h>
#include <rtems/rtems/status.h>
#include <rtems/rtems/types.h>
#include <rtems/rtems/options.h>
#include <rtems/score/thread.h>
#include <rtems/score/threadsync.h>
#include <rtems/score/watchdog.h>
#include <rtems/rtems/eventset.h>
/**
* @defgroup ClassicEvent Events
*
* @ingroup ClassicRTEMS
*
* @brief The event manager provides a high performance method of intertask
* communication and synchronization.
*
* An event flag is used by a task (or ISR) to inform another task of the
* occurrence of a significant situation. Thirty-two event flags are
* associated with each task. A collection of one or more event flags is
* referred to as an event set. The data type rtems_event_set is used to
* manage event sets.
*
* The application developer should remember the following key characteristics
* of event operations when utilizing the event manager:
*
* - Events provide a simple synchronization facility.
* - Events are aimed at tasks.
* - Tasks can wait on more than one event simultaneously.
* - Events are independent of one another.
* - Events do not hold or transport data.
* - Events are not queued. In other words, if an event is sent more than once
* to a task before being received, the second and subsequent send
* operations to that same task have no effect.
*
* An event set is posted when it is directed (or sent) to a task. A pending
* event is an event that has been posted but not received. An event condition
* is used to specify the event set which the task desires to receive and the
* algorithm which will be used to determine when the request is satisfied. An
* event condition is satisfied based upon one of two algorithms which are
* selected by the user. The @ref RTEMS_EVENT_ANY algorithm states that an
* event condition is satisfied when at least a single requested event is
* posted. The @ref RTEMS_EVENT_ALL algorithm states that an event condition
* is satisfied when every requested event is posted.
*
* An event set or condition is built by a bitwise or of the desired events.
* The set of valid events is @ref RTEMS_EVENT_0 through @ref RTEMS_EVENT_31.
* If an event is not explicitly specified in the set or condition, then it is
* not present. Events are specifically designed to be mutually exclusive,
* therefore bitwise or and addition operations are equivalent as long as each
* event appears exactly once in the event set list.
*
* For example, when sending the event set consisting of @ref RTEMS_EVENT_6,
* @ref RTEMS_EVENT_15, and @ref RTEMS_EVENT_31, the event parameter to the
* rtems_event_send() directive should be @ref RTEMS_EVENT_6 |
* @ref RTEMS_EVENT_15 | @ref RTEMS_EVENT_31.
*
* @{
*/
/**
* @brief Sends an event set to the target task.
*
* This directive sends an event set @a event_in to the task specified by
* @a id.
*
* Based upon the state of the target task, one of the following situations
* applies. The target task is
* - blocked waiting for events.
* If the waiting task's input event condition is
* - satisfied, then the task is made ready for execution.
* - not satisfied, then the event set is posted but left pending and the
* task remains blocked.
* - not waiting for events.
* - The event set is posted and left pending.
*
* Identical events sent to a task are not queued. In other words, the second,
* and subsequent, posting of an event to a task before it can perform an
* rtems_event_receive() has no effect.
*
* The calling task will be preempted if it has preemption enabled and a
* higher priority task is unblocked as the result of this directive.
*
* Sending an event set to a global task which does not reside on the local
* node will generate a request telling the remote node to send the event set
* to the appropriate task.
*
* @param[in] id Identifier of the target task. Specifying @ref RTEMS_SELF
* results in the event set being sent to the calling task.
* @param[in] event_in Event set sent to the target task.
*
* @retval RTEMS_SUCCESSFUL Successful operation.
* @retval RTEMS_INVALID_ID Invalid task identifier.
*/
rtems_status_code rtems_event_send (
rtems_id id,
rtems_event_set event_in
);
/**
* @brief Receives pending events.
*
* This directive attempts to receive the event condition specified in
* @a event_in. If @a event_in is set to @ref RTEMS_PENDING_EVENTS, then the
* current pending events are returned in @a event_out and left pending. The
* @aref RTEMS_WAIT and @aref RTEMS_NO_WAIT options in the @a option_set
* parameter are used to specify whether or not the task is willing to wait
* for the event condition to be satisfied. The @ref RTEMS_EVENT_ANY and @ref
* RTEMS_EVENT_ALL are used in the @a option_set parameter to specify whether
* at least a single event or the complete event set is necessary to satisfy
* the event condition. The @a event_out parameter is returned to the calling
* task with the value that corresponds to the events in @a event_in that were
* satisfied.
*
* A task can determine the pending event set by using a value of
* @ref RTEMS_PENDING_EVENTS for the input event set @a event_in. The pending
* events are returned to the calling task but the event set is left
* unaltered.
*
* A task can receive all of the currently pending events by using the a value
* of @ref RTEMS_ALL_EVENTS for the input event set @a event_in and
* @ref RTEMS_NO_WAIT | @ref RTEMS_EVENT_ANY for the option set @a option_set.
* The pending events are returned to the calling task and the event set is
* cleared. If no events are pending then the @ref RTEMS_UNSATISFIED status
* code will be returned.
*
* If pending events satisfy the event condition, then @a event_out is set to
* the satisfied events and the pending events in the event condition are
* cleared. If the event condition is not satisfied and @ref RTEMS_NO_WAIT is
* specified, then @a event_out is set to the currently satisfied events. If
* the calling task chooses to wait, then it will block waiting for the event
* condition.
*
* If the calling task must wait for the event condition to be satisfied, then
* the timeout parameter is used to specify the maximum interval to wait. If
* it is set to @ref RTEMS_NO_TIMEOUT, then the calling task will wait forever.
*
* This directive only affects the events specified in @a event_in. Any
* pending events that do not correspond to any of the events specified in
* @a event_in will be left pending.
*
* A clock tick is required to support the wait with time out functionality of
* this directive.
*
* @param[in] event_in Set of requested events (input events).
* @param[in] option_set Use a bitwise or of the following options
* - @ref RTEMS_WAIT - task will wait for event (default),
* - @ref RTEMS_NO_WAIT - task should not wait,
* - @ref RTEMS_EVENT_ALL - return after all events (default), and
* - @ref RTEMS_EVENT_ANY - return after any events.
* @param[in] ticks Time out in ticks. Use @ref RTEMS_NO_TIMEOUT to wait
* without a time out (potentially forever).
* @param[out] event_out Set of received events (output events).
*
* @retval RTEMS_SUCCESSFUL Successful operation.
* @retval RTEMS_UNSATISFIED Input events not satisfied (only with the
* @ref RTEMS_NO_WAIT option).
* @retval RTEMS_INVALID_ADDRESS The @a event_out pointer is @c NULL.
* @retval RTEMS_TIMEOUT Timed out waiting for events.
*/
rtems_status_code rtems_event_receive (
rtems_event_set event_in,
rtems_option option_set,
rtems_interval ticks,
rtems_event_set *event_out
);
/** @} */
/**
* @defgroup ScoreEvent Event Handler
*
* @ingroup Score
*
* @{
*/
/**
* This constant is passed as the event_in to the
* rtems_event_receive directive to determine which events are pending.
*/
#define EVENT_CURRENT 0
/**
* @brief Event_Manager_initialization
*
* This routine performs the initialization necessary for this manager.
*/
void _Event_Manager_initialization( void );
/**
* @brief Event_Seize
*
* This routine determines if the event condition event_in is
* satisfied. If so or if the no_wait option is enabled in option_set,
* then the procedure returns immediately. If neither of these
* conditions is true, then the calling task is blocked with an
* optional timeout of ticks clock ticks.
*/
void _Event_Seize (
rtems_event_set event_in,
rtems_option option_set,
rtems_interval ticks,
rtems_event_set *event_out
);
/**
* @brief Event_Surrender
*
* This routine determines if the event condition of the_thread
* has been satisfied. If so, it unblocks the_thread.
*/
void _Event_Surrender (
Thread_Control *the_thread
);
/**
* @brief Event_Timeout
*
* This routine is invoked when a task's event receive request
* has not been satisfied after the specified timeout interval.
* The task represented by ID will be unblocked and its status
* code will be set in it's control block to indicate that a timeout
* has occurred.
*/
void _Event_Timeout (
Objects_Id id,
void *ignored
);
/**
* @brief he following defines the synchronization flag used by the
*/
RTEMS_EVENT_EXTERN volatile Thread_blocking_operation_States _Event_Sync_state;
/** @} */
#if defined(RTEMS_MULTIPROCESSING)
#include <rtems/rtems/eventmp.h>
#endif
#ifndef __RTEMS_APPLICATION__
#include <rtems/rtems/event.inl>
#endif
#ifdef __cplusplus
}
#endif
#endif
/* end of include file */
