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/*
ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010 Giovanni Di Sirio.
This file is part of ChibiOS/RT.
ChibiOS/RT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
ChibiOS/RT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @file chbsem.h
* @brief Binary semaphores structures and macros.
*
* @addtogroup binary_semaphores
* @details Binary semaphores related APIs and services.
*
* <h2>Operation mode</h2>
* Binary semaphores are implemented as a set of macros that use the
* existing counting semaphores primitives. The difference between
* counting and binary semaphores is that the counter of binary
* semaphores is not allowed to grow above the value 1. Repeated
* signal operation are ignored. A binary semaphore can thus have
* only two defined states:
* - <b>Taken</b>, when its counter has a value of zero or lower
* than zero. A negative number represent the number of threads
* queued on the binary semaphore.
* - <b>Not taken</b>, when its counter has a value of one.
* .
* Binary semaphores are different from mutexes because there is no
* the concept of ownership, a binary semaphore can be taken by a
* thread and signaled by another thread or an interrupt handler,
* mutexes can only be taken and released by the same thread. Another
* difference is that binary semaphores, unlike mutexes, do not
* implement the priority inheritance protocol.<br>
* In order to use the binary semaphores APIs the @p CH_USE_SEMAPHORES
* option must be enabled in @p chconf.h.
* @{
*/
#ifndef _CHBSEM_H_
#define _CHBSEM_H_
#if CH_USE_SEMAPHORES || defined(__DOXYGEN__)
/**
* @extends Semaphore
*
* @brief Binary semaphore type.
*/
typedef struct {
Semaphore bs_sem;
} BinarySemaphore;
/**
* @brief Data part of a static semaphore initializer.
* @details This macro should be used when statically initializing a semaphore
* that is part of a bigger structure.
*
* @param[in] name the name of the semaphore variable
* @param[in] taken the semaphore initial state
*/
#define _BSEMAPHORE_DATA(name, taken) \
{_SEMAPHORE_DATA(name.bs_sem), ((taken) ? 0 : 1)}
/**
* @brief Static semaphore initializer.
* @details Statically initialized semaphores require no explicit
* initialization using @p chSemInit().
*
* @param[in] name the name of the semaphore variable
* @param[in] taken the semaphore initial state
*/
#define BSEMAPHORE_DECL(name, taken) \
BinarySemaphore name = _BSEMAPHORE_DATA(name, taken)
/**
* @brief Initializes a binary semaphore.
*
* @param[out] bsp pointer to a @p BinarySemaphore structure
* @param[in] taken initial state of the binary semaphore:
* - @a FALSE, the initial state is not taken.
* - @a TRUE, the initial state is taken.
* .
*
* @init
*/
#define chBSemInit(bsp, taken) chSemInit(&(bsp)->bs_sem, (taken) ? 0 : 1)
/**
* @brief Wait operation on the binary semaphore.
*
* @param[in] bsp pointer to a @p BinarySemaphore structure
* @return A message specifying how the invoking thread has been
* released from the semaphore.
* @retval RDY_OK if the binary semaphore has been successfully taken.
* @retval RDY_RESET if the binary semaphore has been reset using
* @p bsemReset().
*
* @api
*/
#define chBSemWait(bsp) chSemWait(&(bsp)->bs_sem)
/**
* @brief Wait operation on the binary semaphore.
*
* @param[in] bsp pointer to a @p BinarySemaphore structure
* @return A message specifying how the invoking thread has been
* released from the semaphore.
* @retval RDY_OK if the binary semaphore has been successfully taken.
* @retval RDY_RESET if the binary semaphore has been reset using
* @p bsemReset().
*
* @sclass
*/
#define chBSemWaitS(bsp) chSemWaitS(&(bsp)->bs_sem)
/**
* @brief Wait operation on the binary semaphore.
*
* @param[in] bsp pointer to a @p BinarySemaphore structure
* @param[in] time the number of ticks before the operation timeouts,
* the following special values are allowed:
* - @a TIME_IMMEDIATE immediate timeout.
* - @a TIME_INFINITE no timeout.
* .
* @return A message specifying how the invoking thread has been
* released from the semaphore.
* @retval RDY_OK if the binary semaphore has been successfully taken.
* @retval RDY_RESET if the binary semaphore has been reset using
* @p bsemReset().
* @retval RDY_TIMEOUT if the binary semaphore has not been signaled or reset
* within the specified timeout.
*
* @api
*/
#define chBSemWaitTimeout(bsp, time) chSemWaitTimeout(&(bsp)->bs_sem, (time))
/**
* @brief Wait operation on the binary semaphore.
*
* @param[in] bsp pointer to a @p BinarySemaphore structure
* @param[in] time the number of ticks before the operation timeouts,
* the following special values are allowed:
* - @a TIME_IMMEDIATE immediate timeout.
* - @a TIME_INFINITE no timeout.
* .
* @return A message specifying how the invoking thread has been
* released from the semaphore.
* @retval RDY_OK if the binary semaphore has been successfully taken.
* @retval RDY_RESET if the binary semaphore has been reset using
* @p bsemReset().
* @retval RDY_TIMEOUT if the binary semaphore has not been signaled or reset
* within the specified timeout.
*
* @sclass
*/
#define chBSemWaitTimeoutS(bsp, time) chSemWaitTimeoutS(&(bsp)->bs_sem, (time))
/**
* @brief Reset operation on the binary semaphore.
* @note The released threads can recognize they were waked up by a reset
* rather than a signal because the @p bsemWait() will return
* @p RDY_RESET instead of @p RDY_OK.
*
* @param[in] bsp pointer to a @p BinarySemaphore structure
* @param[in] taken new state of the binary semaphore
* - @a FALSE, the new state is not taken.
* - @a TRUE, the new state is taken.
* .
*
* @api
*/
#define chBSemReset(bsp, taken) chSemReset(&(bsp)->bs_sem, (taken) ? 0 : 1)
/**
* @brief Reset operation on the binary semaphore.
* @note The released threads can recognize they were waked up by a reset
* rather than a signal because the @p bsemWait() will return
* @p RDY_RESET instead of @p RDY_OK.
* @note This function does not reschedule.
*
* @param[in] bsp pointer to a @p BinarySemaphore structure
* @param[in] taken new state of the binary semaphore
* - @a FALSE, the new state is not taken.
* - @a TRUE, the new state is taken.
* .
*
* @iclass
*/
#define chBSemResetI(bsp, taken) chSemResetI(&(bsp)->bs_sem, (taken) ? 0 : 1)
/**
* @brief Performs a signal operation on a binary semaphore.
*
* @param[in] bsp pointer to a @p BinarySemaphore structure
*
* @api
*/
#define chBSemSignal(bsp) { \
chSysLock(); \
chBSemSignalI((bsp)); \
chSchRescheduleS(); \
chSysUnlock(); \
}
/**
* @brief Performs a signal operation on a binary semaphore.
* @note This function does not reschedule.
*
* @param[in] bsp pointer to a @p BinarySemaphore structure
*
* @iclass
*/
#define chBSemSignalI(bsp) { \
if ((bsp)->bs_sem.s_cnt < 1) \
chSemSignalI(&(bsp)->bs_sem); \
}
/**
* @brief Returns the binary semaphore current state.
*
* @param[in] bsp pointer to a @p BinarySemaphore structure
* @return The binary semaphore current state.
* @retval FALSE if the binary semaphore is not taken.
* @retval TRUE if the binary semaphore is taken.
*
* @iclass
*/
#define chBSemGetStateI(bsp) ((bsp)->bs_sem.s_cnt > 0 ? FALSE : TRUE)
#endif /* CH_USE_SEMAPHORES */
#endif /* _CHBSEM_H_ */
/** @} */
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