/*
*********************************************************************************************************
*                                                uC/OS-II
*                                          The Real-Time Kernel
*                                  MUTUAL EXCLUSION SEMAPHORE MANAGEMENT
*
*                              (c) Copyright 1992-2007, Micrium, Weston, FL
*                                           All Rights Reserved
*
* File    : OS_MUTEX.C
* By      : Jean J. Labrosse
* Version : V2.86
*
* LICENSING TERMS:
* ---------------
*   uC/OS-II is provided in source form for FREE evaluation, for educational use or for peaceful research.  
* If you plan on using  uC/OS-II  in a commercial product you need to contact Micri祄 to properly license 
* its use in your product. We provide ALL the source code for your convenience and to help you experience 
* uC/OS-II.   The fact that the  source is provided does  NOT  mean that you can use it without  paying a 
* licensing fee.
*********************************************************************************************************
*/

#ifndef  OS_MASTER_FILE
#include <ucos_ii.h>
#endif


#if OS_MUTEX_EN > 0
/*
*********************************************************************************************************
*                                            LOCAL CONSTANTS
*********************************************************************************************************
*/

#define  OS_MUTEX_KEEP_LOWER_8   ((INT16U)0x00FFu)
#define  OS_MUTEX_KEEP_UPPER_8   ((INT16U)0xFF00u)

#define  OS_MUTEX_AVAILABLE      ((INT16U)0x00FFu)

/*
*********************************************************************************************************
*                                            LOCAL CONSTANTS
*********************************************************************************************************
*/

static  void  OSMutex_RdyAtPrio(OS_TCB *ptcb, INT8U prio);

/*$PAGE*/
/*
*********************************************************************************************************
*                                   ACCEPT MUTUAL EXCLUSION SEMAPHORE
*
* Description: This  function checks the mutual exclusion semaphore to see if a resource is available.
*              Unlike OSMutexPend(), OSMutexAccept() does not suspend the calling task if the resource is
*              not available or the event did not occur.
*
* Arguments  : pevent     is a pointer to the event control block
*
*              perr       is a pointer to an error code which will be returned to your application:
*                            OS_ERR_NONE         if the call was successful.
*                            OS_ERR_EVENT_TYPE   if 'pevent' is not a pointer to a mutex
*                            OS_ERR_PEVENT_NULL  'pevent' is a NULL pointer
*                            OS_ERR_PEND_ISR     if you called this function from an ISR
*                            OS_ERR_PIP_LOWER    If the priority of the task that owns the Mutex is
*                                                HIGHER (i.e. a lower number) than the PIP.  This error
*                                                indicates that you did not set the PIP higher (lower
*                                                number) than ALL the tasks that compete for the Mutex.
*                                                Unfortunately, this is something that could not be
*                                                detected when the Mutex is created because we don't know
*                                                what tasks will be using the Mutex.
*
* Returns    : == OS_TRUE    if the resource is available, the mutual exclusion semaphore is acquired
*              == OS_FALSE   a) if the resource is not available
*                            b) you didn't pass a pointer to a mutual exclusion semaphore
*                            c) you called this function from an ISR
*
* Warning(s) : This function CANNOT be called from an ISR because mutual exclusion semaphores are
*              intended to be used by tasks only.
*********************************************************************************************************
*/

#if OS_MUTEX_ACCEPT_EN > 0
BOOLEAN  OSMutexAccept (OS_EVENT *pevent, INT8U *perr)
{
    INT8U      pip;                                    /* Priority Inheritance Priority (PIP)          */
#if OS_CRITICAL_METHOD == 3                            /* Allocate storage for CPU status register     */
    OS_CPU_SR  cpu_sr = 0;
#endif



#if OS_ARG_CHK_EN > 0
    if (perr == (INT8U *)0) {                          /* Validate 'perr'                              */
        return (OS_FALSE);
    }
    if (pevent == (OS_EVENT *)0) {                     /* Validate 'pevent'                            */
        *perr = OS_ERR_PEVENT_NULL;
        return (OS_FALSE);
    }
#endif
    if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX) {  /* Validate event block type                    */
        *perr = OS_ERR_EVENT_TYPE;
        return (OS_FALSE);
    }
    if (OSIntNesting > 0) {                            /* Make sure it's not called from an ISR        */
        *perr = OS_ERR_PEND_ISR;
        return (OS_FALSE);
    }
    OS_ENTER_CRITICAL();                               /* Get value (0 or 1) of Mutex                  */
    pip = (INT8U)(pevent->OSEventCnt >> 8);            /* Get PIP from mutex                           */
    if ((pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8) == OS_MUTEX_AVAILABLE) {
        pevent->OSEventCnt &= OS_MUTEX_KEEP_UPPER_8;   /*      Mask off LSByte (Acquire Mutex)         */
        pevent->OSEventCnt |= OSTCBCur->OSTCBPrio;     /*      Save current task priority in LSByte    */
        pevent->OSEventPtr  = (void *)OSTCBCur;        /*      Link TCB of task owning Mutex           */
        if (OSTCBCur->OSTCBPrio <= pip) {              /*      PIP 'must' have a SMALLER prio ...      */
            OS_EXIT_CRITICAL();                        /*      ... than current task!                  */
            *perr = OS_ERR_PIP_LOWER;
        } else {
            OS_EXIT_CRITICAL();
            *perr = OS_ERR_NONE;
        }
        return (OS_TRUE);
    }
    OS_EXIT_CRITICAL();
    *perr = OS_ERR_NONE;
    return (OS_FALSE);
}
#endif

/*$PAGE*/
/*
*********************************************************************************************************
*                                  CREATE A MUTUAL EXCLUSION SEMAPHORE
*
* Description: This function creates a mutual exclusion semaphore.
*
* Arguments  : prio          is the priority to use when accessing the mutual exclusion semaphore.  In
*                            other words, when the semaphore is acquired and a higher priority task
*                            attempts to obtain the semaphore then the priority of the task owning the
*                            semaphore is raised to this priority.  It is assumed that you will specify
*                            a priority that is LOWER in value than ANY of the tasks competing for the
*                            mutex.
*
*              perr          is a pointer to an error code which will be returned to your application:
*                               OS_ERR_NONE         if the call was successful.
*                               OS_ERR_CREATE_ISR   if you attempted to create a MUTEX from an ISR
*                               OS_ERR_PRIO_EXIST   if a task at the priority inheritance priority
*                                                   already exist.
*                               OS_ERR_PEVENT_NULL  No more event control blocks available.
*                               OS_ERR_PRIO_INVALID if the priority you specify is higher that the
*                                                   maximum allowed (i.e. > OS_LOWEST_PRIO)
*
* Returns    : != (void *)0  is a pointer to the event control clock (OS_EVENT) associated with the
*                            created mutex.
*              == (void *)0  if an error is detected.
*
* Note(s)    : 1) The LEAST significant 8 bits of '.OSEventCnt' are used to hold the priority number
*                 of the task owning the mutex or 0xFF if no task owns the mutex.
*
*              2) The MOST  significant 8 bits of '.OSEventCnt' are used to hold the priority number
*                 to use to reduce priority inversion.
*********************************************************************************************************
*/

OS_EVENT  *OSMutexCreate (INT8U prio, INT8U *perr)
{
    OS_EVENT  *pevent;
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
    OS_CPU_SR  cpu_sr = 0;
#endif



#if OS_ARG_CHK_EN > 0
    if (perr == (INT8U *)0) {                              /* Validate 'perr'                          */
        return ((OS_EVENT *)0);
    }
    if (prio >= OS_LOWEST_PRIO) {                          /* Validate PIP                             */
        *perr = OS_ERR_PRIO_INVALID;
        return ((OS_EVENT *)0);
    }
#endif
    if (OSIntNesting > 0) {                                /* See if called from ISR ...               */
        *perr = OS_ERR_CREATE_ISR;                         /* ... can't CREATE mutex from an ISR       */
        return ((OS_EVENT *)0);
    }
    OS_ENTER_CRITICAL();
    if (OSTCBPrioTbl[prio] != (OS_TCB *)0) {               /* Mutex priority must not already exist    */
        OS_EXIT_CRITICAL();                                /* Task already exist at priority ...       */
        *perr = OS_ERR_PRIO_EXIST;                         /* ... inheritance priority                 */
        return ((OS_EVENT *)0);
    }
    OSTCBPrioTbl[prio] = OS_TCB_RESERVED;                  /* Reserve the table entry                  */
    pevent             = OSEventFreeList;                  /* Get next free event control block        */
    if (pevent == (OS_EVENT *)0) {                         /* See if an ECB was available              */
        OSTCBPrioTbl[prio] = (OS_TCB *)0;                  /* No, Release the table entry              */
        OS_EXIT_CRITICAL();
        *perr              = OS_ERR_PEVENT_NULL;           /* No more event control blocks             */
        return (pevent);
    }
    OSEventFreeList        = (OS_EVENT *)OSEventFreeList->OSEventPtr;   /* Adjust the free list        */
    OS_EXIT_CRITICAL();
    pevent->OSEventType    = OS_EVENT_TYPE_MUTEX;
    pevent->OSEventCnt     = (INT16U)((INT16U)prio << 8) | OS_MUTEX_AVAILABLE; /* Resource is avail.   */
    pevent->OSEventPtr     = (void *)0;                                 /* No task owning the mutex    */
#if OS_EVENT_NAME_SIZE > 1
    pevent->OSEventName[0] = '?';
    pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
    OS_EventWaitListInit(pevent);
    *perr                  = OS_ERR_NONE;
    return (pevent);
}

/*$PAGE*/
/*
*********************************************************************************************************
*                                          DELETE A MUTEX
*
* Description: This function deletes a mutual exclusion semaphore and readies all tasks pending on the it.
*
* Arguments  : pevent        is a pointer to the event control block associated with the desired mutex.
*
*              opt           determines delete options as follows:
*                            opt == OS_DEL_NO_PEND   Delete mutex ONLY if no task pending
*                            opt == OS_DEL_ALWAYS    Deletes the mutex even if tasks are waiting.
*                                                    In this case, all the tasks pending will be readied.
*
*              perr          is a pointer to an error code that can contain one of the following values:
*                            OS_ERR_NONE             The call was successful and the mutex was deleted
*                            OS_ERR_DEL_ISR          If you attempted to delete the MUTEX from an ISR
*                            OS_ERR_INVALID_OPT      An invalid option was specified
*                            OS_ERR_TASK_WAITING     One or more tasks were waiting on the mutex
*                            OS_ERR_EVENT_TYPE       If you didn't pass a pointer to a mutex
*                            OS_ERR_PEVENT_NULL      If 'pevent' is a NULL pointer.
*
* Returns    : pevent        upon error
*              (OS_EVENT *)0 if the mutex was successfully deleted.