source: rtems/cpukit/posix/include/rtems/posix/priorityimpl.h @ 5a32c48

/**
 * @file
 * 
 * @brief POSIX Priority Support
 *
 * This include file defines the interface to the POSIX priority
 * implementation.
 */

/*
 *  COPYRIGHT (c) 1989-2011.
 *  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.org/license/LICENSE.
 */

#ifndef _RTEMS_POSIX_PRIORITYIMPL_H
#define _RTEMS_POSIX_PRIORITYIMPL_H

#include <rtems/score/scheduler.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @defgroup POSIX_PRIORITY POSIX Priority Support
 *
 * @ingroup POSIXAPI
 *
 * @brief Interface to the POSIX Priority Implementation.
 *
 * @{
 */

/**
 *  This is the numerically least important POSIX priority.
 */
#define POSIX_SCHEDULER_MINIMUM_PRIORITY (1)

/**
 * @brief Gets the maximum POSIX API priority for this scheduler instance.
 *
 * Such a priority is valid.  A scheduler instance may support priority values
 * that are not representable as an integer.
 *
 * @return The maximum POSIX API priority for this scheduler instance.
 */
int _POSIX_Priority_Get_maximum( const Scheduler_Control *scheduler );

/**
 * @brief Check if POSIX priority is valid.
 * 
 * According to POSIX, numerically higher values represent higher priorities.
 * Thus, SuperCore has priorities run in the opposite sense of the POSIX API.
 *
 * Let N be the maximum priority of this scheduler instance.   The SuperCore
 * priority zero is system reserved (PRIORITY_PSEUDO_ISR).  There are only
 * N - 1 POSIX API priority levels since a thread at SuperCore priority N would
 * never run because of the idle threads.  This is necessary because GNAT maps
 * the lowest Ada task priority to the lowest thread priority.  The lowest
 * priority Ada task should get to run, so there is a fundamental conflict with
 * having N priorities.
 *
 * @param[in] scheduler The scheduler instance.
 * @param[in] priority The POSIX API priority to test.
 *
 * @retval true The priority is valid.
 * @retval false Otherwise.
 */
bool _POSIX_Priority_Is_valid(
  const Scheduler_Control *scheduler,
  int                      priority
);

/**
 * @brief Converts the SuperCore priority to the corresponding POSIX API
 * priority.
 *
 * @param[in] scheduler The scheduler instance.
 * @param[in] priority The SuperCore priority to convert.
 *
 * @return The corresponding POSIX API priority.
 */
RTEMS_INLINE_ROUTINE int _POSIX_Priority_From_core(
  const Scheduler_Control *scheduler,
  Priority_Control         priority
)
{
  return (int) ( scheduler->maximum_priority - priority );
}

/** @} */

#ifdef __cplusplus
}
#endif

#endif