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-@c
-@c COPYRIGHT (c) 1988-2002.
-@c On-Line Applications Research Corporation (OAR).
-@c All rights reserved.
-@c
-@c This is the chapter from the RTEMS ITRON User's Guide that
-@c documents the services provided by the eventflags
-@c manager.
-@c
-@c $Id$
-@c
-
-@chapter Eventflags Manager
-
-@section Introduction
-
-The eventflag manager provides a high performance method of intertask communication and synchronization. The directives provided by the eventflag manager are:
-
-The services provided by the eventflags manager are:
-
-@itemize @bullet
-@item @code{cre_flg} - Create Eventflag
-@item @code{del_flg} - Delete Eventflag
-@item @code{set_flg} - Set Eventflag
-@item @code{clr_flg} - Clear Eventflag
-@item @code{wai_flg} - Wait on Eventflag
-@item @code{pol_flg} - Wait for Eventflag (Polling)
-@item @code{twai_flg} - Wait on Eventflag with Timeout
-@item @code{ref_flg} - Reference Eventflag Status
-@end itemize
-
-@section Background
-
-@subsection Event sets
-
-An eventflag is used by a task (or ISR) to inform another task of the
-occurrence of a significant situation. One word bit-field is associated with each eventflags. The application developer should remember the
-following key characteristics of event operations when utilizing the event
-manager:
-
-@itemize @bullet
-@item Events provide a simple synchronization facility.
-@item Events are aimed at tasks.
-@item Tasks can wait on more than one event simultaneously.
-@item Events are independent of one another.
-@item Events do not hold or transport data.
-@item 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.
-@end itemize
-
-A pending event is an event that has been set. An
-event condition is used to specify the events 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 @code{TWF_ORW} algorithm
-states that an event condition is satisfied when at least a single
-requested event is posted. The @code{TWF_ANDW} algorithm states that an
-event condition is satisfied when every requested event is posted.
-
-An eventflags or condition is built by a bitwise OR of the desired events.
-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.
-
-@subsection T_CFLG Structure
-
-The T_CFLG structire is used to define the characteristics of an eventflag
-and passed as an argument to the @code{cre_flg} service. The structure is
-defined as follows:
-
-@example
-
-/*
- * Create Eventflags (cre_flg) Structure
- */
-
-typedef struct t_cflg @{
- VP exinf; /* extended information */
- ATR flgatr; /* eventflag attribute */
- UINT iflgptn; /* initial eventflag */
- /* additional implementation dependent information may be included */
-@} T_CFLG;
-
-/*
- * flgatr - Eventflag Attribute Values
- */
-
-
-/* multiple tasks are not allowed to wait (Wait Single Task)*/
-
-#define TA_WSGL 0x00
-
-/* multiple tasks are allowed to wait (Wait Multiple Task) */
-
-#define TA_WMUL 0x08
-
-/* wfmode */
-#define TWF_ANDW 0x00 /* AND wait */
-#define TWF_ORW 0x02 /* OR wait */
-#define TWF_CLR 0x01 /* clear specification */
-@end example
-
-where the meaning of each field is:
-
-@table @b
-
-@item exinf
-
-may be used freely by the user for including extended information about
-the eventflag to be created. Information set here may be accessed by
-@code{ref_flg}. If a larger region is desired for including user information, or
-if the user wishes to change the contents of this information, the usr
-should allocate memory area and set the address of this memory packet to
-@code{exinf}. The OS does not take care of the contents of @code{exinf}. This
-implementation does not use this field.
-
-@item flgatr
-
-is the attributes for this eventflag. The lower bits of flgatr represent
-system attributes, while the upper bits represent implementation-dependent
-attributes.
-
-@item iflgptn
-
-is the initial eventflag pattern.
-(CPU and/or implementation-dependent information may also be included)
-
-@end table
-
-@subsection T_RFLG Structure
-
-The T_RFLG structire is used to define the characteristics of an eventflag
-and passed as an argument to the @code{ref_flg} service. The structure is
-defined as follows:
-
-@example
-/* Reference Eventflags (ref_flg) Structure */
-typedef struct t_rflg @{
- VP exinf; /* extended information */
- BOOL_ID wtsk; /* indicates whether or not there is a waiting task */
- UINT flgptn; /* eventflag bit pattern */
- /* additional implementation dependent information may be included */
-@} T_RFLG;
-@end example
-
-@table @b
-
-@item exinf
-
-see @code{T_CFLG}.
-
-@item wtsk
-
-indicates whether or not there is a task waiting for the eventflag in
-question. If there is no waiting task, @code{wtsk} is returned as FALSE = 0.
-If there is a waiting task, @code{wtsk} is returned as a value other than 0.
-
-@item flgptn
-
-is the eventflag pattern.
-
-@end table
-
-@section Operations
-
-@section System Calls
-
-This section details the eventflags manager's services. A subsection is
-dedicated to each of this manager's services and describes the calling
-sequence, related constants, usage, and status codes.
-
-
-@c
-@c cre_flg
-@c
-
-@page
-@subsection cre_flg - Create Eventflag
-
-@subheading CALLING SEQUENCE:
-
-@ifset is-C
-@example
-ER cre_flg(
- ID flgid,
- T_CFLG *pk_cflg
-);
-@end example
-@end ifset
-
-@ifset is-Ada
-@end ifset
-
-@subheading STATUS CODES:
-
-@code{E_OK} - Normal Completion
-
-@code{E_NOMEM} - Insufficient memory (Memory for control block cannot be
-allocated)
-
-@code{E_ID} - Invalid ID number (flgid was invalid or could not be used)
-
-@code{E_RSATR} - Reserved attribute (flgatr was invalid or could not be
-used)
-
-@code{E_OBJ} - Invalid object state (an eventflag of the same ID already
-exists)
-
-@code{E_OACV} - Object access violation (A flgid less than -4 was
-specified from a user task. This is implementation dependent.)
-
-@code{E_PAR} - Parameter error (pk_cflg is invalid)
-
-@code{EN_OBJNO} - An object number which could not be accessed on the
-target node is specified.
-
-@code{EN_CTXID} - Specified an object on another node when the system call
-was issued from a task in dispatch disabled state or from a
-task-independent portion
-
-@code{EN_PAR}- A value outside the range supported by the target node
-and/or transmission packet format was specified as a parameter (a value
-outside supported range was specified for exinf, flgatr and/or iflgptn)
-
-@subheading DESCRIPTION:
-
-This system call creates the eventflag specified by @code{flgid}.
-Specifically, a control block for the eventflag to be created is allocated
-and the associated flag pattern is initialized using @code{iflgptn}. A
-single eventflag handles one word's worth of bits of the processor in
-question as a group. All operations are done in single word units.
-
-User eventflags have positive ID numbers, while system eventflags have
-negative ID numbers. User tasks (tasks having positive task IDs) cannot
-access system eventflags. An @code{E_OACV} error will result if a user
-task issues a system call on a system eventflag, but error detection is
-implementation dependent.
-
-Eventflags having ID numbers from -4 through 0 cannot be created. An
-@code{E_ID} error will result if a value in this range is specified for
-@code{flgid}.
-
-The system attribute part of @code{flgatr} may be specified as @code{TA_WSGL}
-(Wait Single Task) or @code{TA_WMUL} (Wait Multiple Tasks)
-
-@subheading NOTES:
-
-Multiprocessing is not supported. Thus none of the "@code{EN_}" status
-codes will be returned.
-
-All memory is preallocated for @code{RTEMS ITRON} objects. Thus, no
-dynamic memory allocation is performed by @code{cre_flg} and the
-@code{E_NOMEM} error can not be returned.
-
-@c
-@c del_flg
-@c
-
-@page
-@subsection del_flg - Delete Eventflag
-
-@subheading CALLING SEQUENCE:
-
-@ifset is-C
-@example
-ER del_flg(
- ID flgid
-);
-@end example
-@end ifset
-
-@ifset is-Ada
-@end ifset
-
-@subheading STATUS CODES:
-
-@code{E_OK} - Normal Completion
-
-@code{E_ID} - Invalid ID number (flgid was invalid or could not be used)
-
-@code{E_NOEXS} - Object does not exist (the eventflag specified by flgid
-does not exist)
-
-@code{E_OACV} - Object access violation (A flgid less than -4 was
-specified from a user task. This is implementation dependent.)
-
-@code{EN_OBJNO} - An object number which could not be accessed on the
-target node is specified.
-
-@code{EN_CTXID} - Specified an object on another node when the system call
-was issued from a task in dispatch disabled state or from a
-task-independent portion
-
-@subheading DESCRIPTION:
-
-This system call deletes the eventflag specified by @code{flgid}.
-
-Issuing this system call causes memory used for the control block of the
-associated eventflag to be released. After this system call is invoked,
-another eventflag having the same ID number can be created.
-
-This system call will complete normally even if there are tasks waiting
-for the eventflag. In that case, an @code{E_DLT} error will be returned
-to each waiting task.
-
-@subheading NOTES:
-
-Multiprocessing is not supported. Thus none of the "@code{EN_}" status
-codes will be returned.
-
-When an eventflag being waited for by more than one tasks is deleted, the
-order of tasks on the ready queue after the WAIT state is cleared is
-implementation dependent in the case of tasks having the same priority.
-
-@c
-@c set_flg
-@c
-
-@page
-@subsection set_flg - Set Eventflag
-
-@subheading CALLING SEQUENCE:
-
-@ifset is-C
-@example
-ER set_flg(
- ID flgid,
- UINT setptn
-);
-@end example
-@end ifset
-
-@ifset is-Ada
-@end ifset
-
-@subheading STATUS CODES:
-
-@code{E_OK} - Normal Completion
-
-@code{E_ID} - Invalid ID number (flgid was invalid or could not be used)
-
-@code{E_NOEXS} - Object does not exist (the eventflag specified by flgid
-does not exist)
-
-@code{E_OACV} - Object access violation (A flgid less than -4 was
-specified from a user task. This is implementation dependent.)
-
-@code{EN_OBJNO} - An object number which could not be accessed on the
-target node is specified.
-
-@code{EN_CTXID} - Specified an object on another node when the system call
-was issued from a task in dispatch disabled state or from a
-task-independent portion
-
-@code{EN_PAR} - A value outside the range supported by the target node
-and/or transmission packet format was specified as a parameter (a value
-outside supported range was specified for setptn or clrptn)
-
-@subheading DESCRIPTION:
-
-The @code{set_flg} system call sets the bits specified by @code{setptn} of the
-one word eventflag specified by @code{flgid}. In other words, a logical
-sum is taken for the values of the eventflag specified by @code{flgid} with the
-value of @code{setptn}.
-
-If the eventflag value is changed by @code{set_flg} and the new eventflag
-value satisfies the condition to release the WAIT state of the task which
-issued @code{wai_flg} on the eventflag, the WAIT state of that task will
-be released and the task will be put into RUN or READY state (or SUSPEND
-state if the task was in WAIT-SUSPEND).
-
-Nothing will happen to the target eventflag if all bits of @code{setptn}
-are specified as 0 with @code{set_flg}. No error will result in either
-case.
-
-Multiple tasks can wait for a single eventflag if that eventflags has the
-@code{TA_WMUL} attribute. This means that even eventflags can make queues
-for tasks to wait on. When such eventflags are used, a single
-@code{set_flg} call may result in the release of multiple waiting tasks.
-In this case, the order of tasks on the ready queue after the WAIT state
-is cleared is preserved for tasks having the same priority.
-
-@subheading NOTES:
-
-Multiprocessing is not supported. Thus none of the "@code{EN_}" status
-codes will be returned.
-
-@c
-@c clr_flg
-@c
-
-@page
-@subsection clr_flg - Clear Eventflag
-
-@subheading CALLING SEQUENCE:
-
-@ifset is-C
-@example
-ER clr_flg(
- ID flgid,
- UINT clrptn
-);
-@end example
-@end ifset
-
-@ifset is-Ada
-@end ifset
-
-@subheading STATUS CODES:
-
-
-@code{E_OK} - Normal Completion
-
-@code{E_ID} - Invalid ID number (flgid was invalid or could not be used)
-
-@code{E_NOEXS} - Object does not exist (the eventflag specified by flgid
-does not exist)
-
-@code{E_OACV} - Object access violation (A flgid less than -4 was
-specified from a user task. This is implementation dependent.)
-
-@code{EN_OBJNO} - An object number which could not be accessed on the
-target node is specified.
-
-@code{EN_CTXID} - Specified an object on another node when the system call
-was issued from a task in dispatch disabled state or from a
-task-independent portion
-
-@code{EN_PAR} - A value outside the range supported by the target node
-and/or transmission packet format was specified as a parameter (a value
-outside supported range was specified for setptn or clrptn)
-
-@subheading DESCRIPTION:
-
-The @code{clr_flg} system call clears the bits of the one word eventflag
-based on the corresponding zero bits of @code{clrptn}. In other words, a
-logical product is taken for the values of the eventflag specified by
-@code{flgid} with the value of @code{clrptn}.
-
-Issuing @code{clr_flg} never results in wait conditions being released on
-a task waiting for the specified eventflag. In other words, dispatching
-never occurs with @code{clr_flg}.
-
-Nothing will happen to the target eventflag if all bits of @code{clrptn}
-are specified as 1 with @code{clr_flg}. No error will result.
-
-@subheading NOTES:
-
-Multiprocessing is not supported. Thus none of the "@code{EN_}" status
-codes will be returned.
-
-@c
-@c wai_flg
-@c
-
-@page
-@subsection wai_flg - Wait on Eventflag
-
-@subheading CALLING SEQUENCE:
-
-@ifset is-C
-@example
-ER wai_flg(
- UINT *p_flgptn,
- ID flgid,
- UINT waiptn,
- UINT wfmode
-);
-@end example
-@end ifset
-
-@ifset is-Ada
-@end ifset
-
-@subheading STATUS CODES:
-
-
-@code{E_OK} - Normal Completion
-
-@code{E_ID} - Invalid ID number (flgid was invalid or could not be used)
-
-@code{E_NOEXS} - Object does not exist (the eventflag specified by flgid
-does not exist)
-
-@code{E_OACV} - Object access violation (A flgid less than -4 was
-specified from a user task. This is implementation dependent.)
-
-@code{E_PAR} - Parameter error (waiptn = 0, wfmode invalid, or tmout is -2
-or less)
-
-@code{E_OBJ} - Invalid object state (multiple tasks waiting for an
-eventflag with the TA_WSGL attribute)
-
-@code{E_DLT} - The object being waited for was deleted (the specified
-eventflag was deleted while waiting)
-
-@code{E_RLWAI} - WAIT state was forcibly released (rel_wai was received
-while waiting)
-
-@code{E_TMOUT} - Polling failure or timeout exceeded
-
-@code{E_CTX} - Context error (issued from task-independent portions or a
-task in dispatch disabled state)
-
-@code{EN_OBJNO} - An object number which could not be accessed on the
-target node is specified.
-
-@code{EN_PAR} - A value outside the range supported by the target node
-and/or transmission packet format was specified as a parameter (a value
-outside supported range was specified for waiptn and tmout)
-
-@code{EN_RPAR} - A value outside the range supported by the requesting
-node and/or transmission packet format was specified as a parameter (a
-value exceeding the range for the requesting node was specified for
-flgptn)
-
-@subheading DESCRIPTION:
-
-The @code{wai_flg} system call waits for the eventflag specified by
-@code{flgid} to be set to satisfy the wait release condition specified by
-@code{wfmode}. The Eventflags bit-pattern will be returned with a pointer @code{p_flgptn}.
-
-If the eventflag specified by @code{flgid} already satisfies the wait
-release conditions given by @code{wfmode}, the issuing task will continue
-execution without waiting. @code{wfmode} may be specified as follows.
-
-@example
- wfmode = TWF_ANDW (or TWF_ORW) | TWF_CLR(optional)
-@end example
-
-If @code{TWF_ORW} is specified, the issuing task will wait for any of the
-bits specified by @code{waiptn} to be set for the eventflag given by
-@code{flgid} (OR wait). If @code{TWF_ANDW} is specified, the issuing task
-will wait for all of the bits specified by @code{waiptn} to be set for the
-eventflag given by @code{flgid} (AND wait).
-
-If the @code{TWF_CLR} specification is not present, the eventflag value
-will remain unchanged even after the wait conditions have been satisfied
-and the task has been released from the WAIT state. If @code{TWF_CLR} is
-specified, all bits of the eventflag will be cleared to 0 once the wait
-conditions of the waiting task have been satisfied.
-
-The return parameter @code{flgptn} returns the value of the eventflag after the
-wait state of a task has been released due to this system call. If
-@code{TWF_CLR} was specified, the value before eventflag bits were cleared
-is returned. The value returned by @code{flgptn} fulfills the wait
-release conditions of this system call.
-
-An @code{E_PAR} parameter error will result if @code{waiptn} is 0.
-
-A task can not execute any of @code{wai_flg, twai_flg} or @code{pol_flg}
-on an eventflag having the @code{TA_WSGL} attribute if another task is
-already waiting for that eventflag. An @code{E_OBJ} error will be
-returned to a task which executes @code{wai_flg} at a later time
-regardless as to whether or not the task that executes @code{wai_flg} or
-@code{twai_flg} later will be placed in a WAIT state (conditions for
-releasing wait state be satisfied). An @code{E_OBJ} error will be
-returned even to tasks which just execute @code{pol_flg}, again regardless
-as to whether or not wait release conditions for that task were satisfied.
-
-On the other hand, multiple tasks can wait at the same time for the same
-eventflag if that eventflag has the @code{TA_WMUL} attribute. This means
-that event flags can make queues for tasks to wait on. When such
-eventflags are used, a single @code{set_flg} call may release multiple
-waiting tasks.
-
-The following processing takes place if a queue for allowing multiple
-tasks to wait has been created for an eventflag with the @code{TA_WMUL}
-attribute.
-
-@itemize @bullet
-
-@item The waiting order on the queue is FIFO. (However, depending on
-@code{waiptn} and @code{wfmode}, task at the head of the queue will not
-always be released from waiting.)
-
-@item If a task specifying that the eventflag be cleared is on the queue,
-the flag is cleared when that task is released from waiting.
-
-@item Since any tasks behind a task which clears the eventflag (by
-specifying @code{TWF_CLR}) will check the eventflag after it is cleared,
-they will not be released from waiting.
-
-@end itemize
-
-If multiple tasks having the same priority are released from waiting
-simultaneously due to @code{set_flg}, the order of tasks on the ready
-queue after release will be the same as their original order on the
-eventflag queue.
-
-@subheading NOTES:
-
-Multiprocessing is not supported. Thus none of the "@code{EN_}" status
-codes will be returned.
-
-
-@c
-@c pol_flg
-@c
-
-@page
-@subsection pol_flg - Wait for Eventflag (Polling)
-
-@subheading CALLING SEQUENCE:
-
-@ifset is-C
-@example
-ER pol_flg(
- UINT *p_flgptn,
- ID flgid,
- UINT waiptn,
- UINT wfmode
-);
-@end example
-@end ifset
-
-@ifset is-Ada
-@end ifset
-
-@subheading STATUS CODES:
-
-
-@code{E_OK} - Normal Completion
-
-@code{E_ID} - Invalid ID number (flgid was invalid or could not be used)
-
-@code{E_NOEXS} - Object does not exist (the eventflag specified by flgid
-does not exist)
-
-@code{E_OACV} - Object access violation (A flgid less than -4 was
-specified from a user task. This is implementation dependent.)
-
-@code{E_PAR} - Parameter error (waiptn = 0, wfmode invalid, or tmout is -2
-or less)
-
-@code{E_OBJ} - Invalid object state (multiple tasks waiting for an
-eventflag with the TA_WSGL attribute)
-
-@code{E_DLT} - The object being waited for was deleted (the specified
-eventflag was deleted while waiting)
-
-@code{E_RLWAI} - WAIT state was forcibly released (rel_wai was received
-while waiting)
-
-@code{E_TMOUT} - Polling failure or timeout exceeded
-
-@code{E_CTX} - Context error (issued from task-independent portions or a
-task in dispatch disabled state)
-
-@code{EN_OBJNO} - An object number which could not be accessed on the
-target node is specified.
-
-@code{EN_PAR} - A value outside the range supported by the target node
-and/or transmission packet format was specified as a parameter (a value
-outside supported range was specified for waiptn and tmout)
-
-@code{EN_RPAR} - A value outside the range supported by the requesting
-node and/or transmission packet format was specified as a parameter (a
-value exceeding the range for the requesting node was specified for
-flgptn)
-
-@subheading DESCRIPTION:
-
-The @code{pol_flg} system call has the same function as @code{wai_flg}
-except for the waiting feature. @code{pol_flg} polls whether or not the
-task should wait if @code{wai_flg} is executed. The meanings of
-parameters to @code{pol_flg} are the same as for @code{wai_flg}. The
-specific operations by @code{pol_flg} are as follows.
-
-@itemize @bullet
-
-@item If the target eventflag already satisfies the conditions for
-releasing wait given by @code{wfmode}, processing is the same as
-@code{wai_flg}: the eventflag is cleared if @code{TWF_CLR} is specified
-and the system call completes normally.
-
-@item If the target eventflag does not yet satisfy the conditions for
-releasing wait given by @code{wfmode}, an @code{E_TMOUT} error is returned to
-indicate polling failed and the system call finishes. Unlike
-@code{wai_flg}, the issuing task does not wait in this case. The eventflag
-is not cleared in this case even if @code{TWF_CLR} has been specified.
-
-@end itemize
-
-@subheading NOTES:
-
-Multiprocessing is not supported. Thus none of the "@code{EN_}" status
-codes will be returned.
-
-
-@c
-@c twai_flg
-@c
-
-@page
-@subsection twai_flg - Wait on Eventflag with Timeout
-
-@subheading CALLING SEQUENCE:
-
-@ifset is-C
-@example
-ER twai_flg(
- UINT *p_flgptn,
- ID flgid,
- UINT waiptn,
- UINT wfmode,
- TMO tmout
-);
-@end example
-@end ifset
-
-@ifset is-Ada
-@end ifset
-
-@subheading STATUS CODES:
-
-
-@code{E_OK} - Normal Completion
-
-@code{E_ID} - Invalid ID number (flgid was invalid or could not be used)
-
-@code{E_NOEXS} - Object does not exist (the eventflag specified by flgid
-does not exist)
-
-@code{E_OACV} - Object access violation (A flgid less than -4 was
-specified from a user task. This is implementation dependent.)
-
-@code{E_PAR} - Parameter error (waiptn = 0, wfmode invalid, or tmout is -2
-or less)
-
-@code{E_OBJ} - Invalid object state (multiple tasks waiting for an
-eventflag with the TA_WSGL attribute)
-
-@code{E_DLT} - The object being waited for was deleted (the specified
-eventflag was deleted while waiting)
-
-@code{E_RLWAI} - WAIT state was forcibly released (rel_wai was received
-while waiting)
-
-@code{E_TMOUT} - Polling failure or timeout exceeded
-
-@code{E_CTX} - Context error (issued from task-independent portions or a
-task in dispatch disabled state)
-
-@code{EN_OBJNO} - An object number which could not be accessed on the
-target node is specified.
-
-@code{EN_PAR} - A value outside the range supported by the target node
-and/or transmission packet format was specified as a parameter (a value
-outside supported range was specified for waiptn and tmout)
-
-@code{EN_RPAR} - A value outside the range supported by the requesting
-node and/or transmission packet format was specified as a parameter (a
-value exceeding the range for the requesting node was specified for
-flgptn)
-
-@subheading DESCRIPTION:
-
-The @code{twai_flg} system call has the same function as @code{wai_flg}
-with an additional timeout feature. A maximum wait time (timeout value)
-can be specified using the parameter @code{tmout}. When a timeout is specified,
-a timeout error, @code{E_TMOUT}, will result and the system call will
-finish if the period specified by @code{tmout} elapses without conditions for
-releasing wait being satisfied.
-
-Specifying @code{TMO_POL = 0} to @code{twai_flg} for @code{tmout} indicates that
-a timeout value of 0 be used, resulting in exactly the same processing as
-@code{pol_flg}. Specifying @code{TMO_FEVR = -1} to @code{twai_flg} for
-@code{tmout} indicates that an infinite timeout value be used, resulting in
-exactly the same processing as @code{wai_flg}.
-
-@subheading NOTES:
-
-Multiprocessing is not supported. Thus none of the "@code{EN_}" status
-codes will be returned.
-
-
-@code{Pol_flg} and @code{wai_flg} represent the same processing as
-specifying certain values (@code{TMO_POL} or @code{TMO_FEVR}) to
-@code{twai_flg} for tmout. As such, only @code{twai_flg} is implemented
-in the kernel; @code{pol_flg} and @code{wai_flg} should be implemented as macros
-which call @code{twai_flg}.
-
-@c
-@c ref_flg
-@c
-
-@page
-@subsection ref_flg - Reference Eventflag Status
-
-@subheading CALLING SEQUENCE:
-
-@ifset is-C
-@example
-ER ref_flg(
- T_RFLG *pk_rflg,
- ID flgid );
-@end example
-@end ifset
-
-@ifset is-Ada
-@end ifset
-
-@subheading STATUS CODES:
-
-
-@code{E_OK} - Normal Completion
-
-@code{E_ID} - Invalid ID number (flgid was invalid or could not be used)
-
-@code{E_NOEXS} - Object does not exist (the eventflag specified by flgid
-does not exist)
-
-@code{E_OACV} - Object access violation (A flgid less than -4 was
-specified from a user task. This is implementation dependent.)
-
-@code{E_PAR} - Parameter error (the packet address for the return
-parameters could not be used)
-
-@code{EN_OBJNO} - An object number which could not be accessed on the
-target node is specified.
-
-@code{EN_CTXID} - Specified an object on another node when the system call
-was issued from a task in dispatch disabled state or from a
-task-independent portion
-
-@code{EN_RPAR} - A value outside the range supported by the requesting
-node and/or transmission packet format was returned as a parameter (a
-value outside supported range was specified for exinf, wtsk and/or flgptn)
-
-@subheading DESCRIPTION:
-
-This system call refers to the state of the eventflag specified by
-@code{flgid}, and returns its current flag pattern (@code{flgptn}),
-waiting task information (@code{wtsk}), and its extended information
-(@code{exinf}).
-
-Depending on the implementation, @code{wtsk} may be returned as the ID
-(non-zero) of the task waiting for the eventflag. If there are multiple
-tasks waiting for the eventflag (only when attribute is @code{TA_WMUL}),
-the ID of the task at the head of the queue is returned.
-
-An @code{E_NOEXS} error will result if the eventflag specified to
-@code{ref_flg} does not exist.
-
-@subheading NOTES:
-
-Multiprocessing is not supported. Thus none of the "@code{EN_}" status
-codes will be returned.
-
-Although both @code{ref_flg} and @code{pol_flg} can be used to find an
-eventflag's pattern (@code{flgptn}) without causing the issuing task to
-wait, @code{ref_flg} simply reads the eventflag's pattern (@code{flgptn})
-while @code{pol_flg} functions is identical to @code{wai_flg} when wait
-release conditions are satisfied (it clears the eventflag if
-@code{TWF_CLR} is specified).
-
-Depending on the implementation, additional information besides
-@code{wtsk} and @code{flgptn} (such as eventflag attributes,
-@code{flgatr}) may also be referred.
generated by cgit v1.2.3 (git 2.25.1) at 2024-04-26 19:35:37 +0000