/****************************************************************************
 * Copyright (c) 2006 DST Technologies Inc.  All Rights Reserved.   
 *
 * Module:  EVENTS
 *
 * Description: This is a decent implementation of events under Linux.
 *
 * Notes:   This implementation poses some limitations, some of which can
 *          be changed by adjusting some defines:
 *        - Max number of events, shared and local, in the system is
 *          defined by MAX_NOF_EVENTS
 *        - Max number of processes that can share the same event at
 *          any given time is defined by MAX_NOF_PROCS
 *        - When a event is deleted, all tasks within the calling process
 *          that may be pending on the event will be unlocked with an
 *          error code.
 *
 ***************************************************************************/

/*============================
 * Includes
 *===========================*/
#include "lld_os.h"
#include "dsthallocal.h"
#include "lld_local.h"
#include "os.h"

/*============================
 * Defines
 *===========================*/
#define UNUSED_EVENT            0xffffffff
#define SIGNALED                1
#define NOT_SIGNALED            0
#define INVALID_PID             0xffffffff  /* Invalid process ID   */
#define Event(i)                (EventsPtr->_Events[i])
#define EventPtr(i)             (&(EventsPtr->_Events[i]))

/*============================
 * Structures
 *===========================*/
typedef struct 
{
    DS_U32  Status;                     /* = UNUSED_EVENT if not used       */
    DS_U32  Name;                       /* 0 for local events               */
    DS_U32  OwnerPid[MAX_NOF_PROCS];    /* Owner process IDs. Contains      */
                                        /* INVALID_PID for non used entries */
    WAIT_Q  WaitQ;                      /* Queue of processes waiting on    */
                                        /* the event                        */
}EVNT_STR;

typedef struct
{
    EVNT_STR _Events[MAX_NOF_EVENTS];
}EVENTS;

/*============================
 * Shared variables
 *===========================*/
static EVENTS *EventsPtr = NULL;        /* Pointer to events area */

/*============================
 * Prototypes
 *===========================*/
static DS_U32 EventCreate (DS_U32 EventName, DS_BOOL Signaled, DS_U32 *EvntId);
static DS_U32 EventWait   (DS_U32 EvntId, DS_U32 Timeout, DS_U32 *TimeLeft,
                           DS_U32 AutoReset);
static DS_U32 EventSet    (DS_U32 EvntId);
static DS_U32 EventReset  (DS_U32 EvntId);
static DS_U32 EventDelete (DS_U32 EvntId);
static DS_U32 EventInfo   (DS_U32 EvntId, DS_U32 *Size, void *Dest);
static EVNT_STR *GetEvPtr (DS_U32 EvntId, DS_U32 *ProcIndex);

/*^^***************************************************************************
 * void EventInit (void)
 *
 * Description: Initialize kernel events for first use
 *
 * Entry :  None
 *
 * Return:  None
 *
 * Notes :
 *
 **************************************************************************^^*/
void EventInit (void)
{
    DS_U32 i;
    EVNT_STR *EvPtr;

    /*=======================================
     * Allocate shared mem for events
     *======================================*/
    if (EventsPtr == NULL)
    {
        EventsPtr = lld_os_malloc (sizeof(EVENTS));

        /*=======================================
         * Initialize events array
         *======================================*/
        for (i=0; i<MAX_NOF_EVENTS; i++)
        {
            EvPtr = EventPtr(i);
            EvPtr->Status = UNUSED_EVENT;
        }
    }
}

/*^^***************************************************************************
 * void EventCleanup (void)
 *
 * Description: Cleanup for module shutdown
 *
 * Entry :  None
 *
 * Return:  None
 *
 * Notes :
 *
 **************************************************************************^^*/
void EventCleanup (void)
{
    if (EventsPtr != NULL)
    {
        lld_os_free (EventsPtr);
    }
}

/*^^***************************************************************************
 * void EventProcessExit (void)
 *
 * Description: Cleanup for all events when a process exits normally
 *              or upnormally.
 *
 * Entry :  None
 *
 * Return:  None
 *
 * Notes :  
 *
 **************************************************************************^^*/
void EventProcessExit (void)
{
    DS_U32  i, j, k, ProcId;
    EVNT_STR *EvPtr;

    ProcId = mCurrentPid;

    /*================================
     * For all events in the system
     *===============================*/
    for (i=0; i<MAX_NOF_EVENTS; i++)
    {
        EvPtr = EventPtr(i);
        /*===============================
         * If event exist
         *==============================*/
        if (EvPtr->Status != UNUSED_EVENT)
        {
            k = 0;                                  /* Ev reference count */
            /*===============================
             * Find ev reference count
             *==============================*/
            for (j=0; j<MAX_NOF_PROCS; j++)
            {
                /*=======================================
                 * If the terminating proc owns the ev
                 * remove it from the list
                 *======================================*/
                if (EvPtr->OwnerPid[j] == ProcId)
                {
                    EvPtr->OwnerPid[j] = INVALID_PID;
                }
                if (EvPtr->OwnerPid[j] != INVALID_PID)
                {
                    k++;                    /* Other process owns the event */
                }
            }
            /*============================================
             * If no other processes reference the ev
             *===========================================*/
            if (k == 0)
            {
                EvPtr->Status = UNUSED_EVENT;
            }
        }
    }
}

/*^^***************************************************************************
 * DS_U32 EventOperation (OBJ_OPER *EvPrm)
 *
 * Description: Perform event operation defined in EvPrm
 *
 * Entry :  EvPrm = Pointer to OBJ_OPER struc holding the requested operation.
 *
 * Return:  0 or -ERESTARTSYS
 *          EvPrm.RetCode hold return values (varies by the opcode)
 *          EvPrm.Prm2 will also be set as follows:
 *            Create: EvPrm.Prm2 = Event ID. = 0 if any error.
 *            Wait:   EvPrm.Prm2 = Adjusted timeout if ret due to signal
 *            Info:   EvPrm.Prm2 = Info size
 *
 * Notes :
 *
 **************************************************************************^^*/
DS_U32 EventOperation (OBJ_OPER *EvPrm)
{
    switch (EvPrm->Opcode)
    {
        case OBJ_OPCODE_CREATE:
            EvPrm->RetCode = EventCreate (EvPrm->Prm1, EvPrm->Prm2, 
                                          &(EvPrm->Prm2));
            break;
        case OBJ_OPCODE_DELETE:
            EvPrm->RetCode = EventDelete (EvPrm->Prm1);
            break;
        case OBJ_OPCODE_WAIT:
            EvPrm->RetCode = EventWait (EvPrm->Prm1, EvPrm->Prm2, 
                                        &(EvPrm->Prm2), EvPrm->RetCode);
            if (EvPrm->RetCode == OBJ_SIGNAL_RCV)
            {
                return (ERR_RESTART_SYS);
            }
            break;
        case OBJ_OPCODE_SET:
            EvPrm->RetCode = EventSet (EvPrm->Prm1);
            break;
        case OBJ_OPCODE_RESET:
            EvPrm->RetCode = EventReset (EvPrm->Prm1);
            break;
        case OBJ_OPCODE_INFO:
            EvPrm->RetCode = EventInfo (EvPrm->Prm1, &(EvPrm->Prm2), 
                                        (void *)(EvPrm->Prm2));
            break;
        default:
            EvPrm->RetCode = OBJ_INVALID_OP;
            break;
    }
    return (0);
}

/*^^***************************************************************************
 * static DS_U32 EventCreate (DS_U32 EventName, DS_BOOL Signaled, DS_U32 *EvntId)
 *
 * Description: Creates an event object with the specified status
 *
 * Entry :  EventName  = Unique number identifying the event.
 *                       Set to NULL to create unnamed event (can not be
 *                       used for inter-process synchronization)
 *          Status     = Initial status (Set=_TRUE_, Reset=_FALSE_)
 *          EvntId     = Pointer to receive event ID
 *
 * Return:  Entry EvntId holds event ID. =0 if any error. Return codes are:
 *          OBJ_OK              Operation completed
 *          OBJ_INVALID_ID      Invalid ev id or process does not own ev
 *          OBJ_MAX_PROCS       Max number of procs reached
 *          OBJ_MAX_OBJS        Max number of events reached
 *
 * Notes :  If the same process creates a shared event multiple times,
 *          it's pid will appear in the event's OwnerPid list only once.
 *          In this case, only one delete is required by the calling process
 *          to delete the event.
 *
 **************************************************************************^^*/
static DS_U32 EventCreate (DS_U32 EventName, DS_BOOL Signaled, DS_U32 *EvntId)
{
    DS_U32 i, j;
    EVNT_STR *EvPtr = NULL;

    *EvntId = 0;
    if (EventsPtr == NULL)
    {
        return (OBJ_INVALID_ID);
    }

    /*================================
     * If shared event
     *===============================*/
    if (EventName != 0)
    {
        /*===========================================
         * Find if shared ev exist (same name)
         *==========================================*/
        for (i=0; i<MAX_NOF_EVENTS; i++)
        {
            EvPtr = EventPtr(i);
            if ((EvPtr->Status != UNUSED_EVENT) && (EvPtr->Name == EventName))
            {
                /*===============================================
                 * Find if current process already owns the ev
                 *==============================================*/
                for (j=0; j<MAX_NOF_PROCS; j++)
                {
                    if (EvPtr->OwnerPid[j] == mCurrentPid)
                    {
                        *EvntId = (i+1);
                        return (OBJ_OK);
                    }
                }
                /*===============================================
                 * No, add process to owners list
                 *==============================================*/
                for (j=0; j<MAX_NOF_PROCS; j++)
                {
                    if (EvPtr->OwnerPid[j] == INVALID_PID)
                    {
                        EvPtr->OwnerPid[j] = mCurrentPid;
                        *EvntId = (i+1);
                        return (OBJ_OK);
                    }
                }
                return (OBJ_MAX_PROCS);
            }
        }
    }

    /*======================================================
     * If ev does not exist or local ev, create new one
     *=====================================================*/
    for (i=0; i<MAX_NOF_EVENTS; i++)
    {
        EvPtr = EventPtr(i);
        if (EvPtr->Status == UNUSED_EVENT)
        {
            if (Signaled)
            {
                EvPtr->Status = SIGNALED;
            }
            else
            {
                EvPtr->Status = NOT_SIGNALED;
            }
            EvPtr->Name = EventName;
            for (j=0; j<MAX_NOF_PROCS; j++)
            {
                EvPtr->OwnerPid[j] = INVALID_PID;
            }
            EvPtr->OwnerPid[0] = mCurrentPid;
            lld_init_wait_q (&(EvPtr->WaitQ));
            *EvntId = (i+1);
            return (OBJ_OK);
        }
    }
    return (OBJ_MAX_OBJS);
}

/*^^***************************************************************************
 * static DS_U32 EventWait (DS_U32 EvntId, DS_U32 Timeout, DS_U32 *TimeLeft,
 *                          DS_U32 AutoReset)
 *
 * Description: Locks a event (decrement count) with a timeout
 *
 * Entry :  EvntId    = Returned by EventCreate
 *          Timeout   = In 1/100 of a second increments.
 *                      = 0 to return immidiately if the resource not available
 *                      = 0xffffffff to wait forever on the resource
 *          TimeLeft  = Pointer to DS_U32 to receive remaining timeout if the
 *                      wait operation interrupted by a signal (if return value
 *                      is OBJ_SIGNAL_RCV)
 *          AutoReset = _TRUE_ to reset the event after receiving it
 *
 * Return:  OBJ_OK              Operation completed
 *          OBJ_INVALID_ID      Invalid ev id or process does not own ev
 *          OBJ_TIMEOUT         Timedout
 *          OBJ_SIGNAL_RCV      Signal received
 *
 * Notes :  - If ev status = SIGNALED and AutoReset = _FALSE_, the function will
 *            return immediately with OBJ_OK
 *          - If ev status = SIGNALED and AutoReset = _TRUE_, Status will be set
 *            to NOT_SIGNALED and the function will return with OBJ_OK
 *          - If ev status = NOT_SIGNALED and timeout = 0, will return TIMEOUT
 *          - If ev status = NOT_SIGNALED and timeout > 0, other processes will
 *            be scheduled until either timeout is elapsed (return TIMEOUT), 
 *            the calling process detects that ev state > 0 (return OK) or the 
 *            process receives a signal (return SIGNAL_RCV)
 *
 *          **** VERY IMPORTANT ***
 *          This locking mechanism does not support priority inversion since
 *          linux does not support (_TRUE_) task priorities.
 *
 **************************************************************************^^*/
static DS_U32 EventWait (DS_U32 EvntId, DS_U32 Timeout, DS_U32 *TimeLeft,
                         DS_U32 AutoReset)
{
    DS_U32 i, Idx;
    EVNT_STR *EvPtr;

    while (_TRUE_)
    {
        /*===========================================
         * Make sure ev still exist (not deleted)
         *==========================================*/
        EvPtr = GetEvPtr(EvntId, &Idx);
        if (EvPtr == NULL)
        {
            return (OBJ_INVALID_ID);
        }

        /*==========================
         * If event is signaled
         *=========================*/
        if (EvPtr->Status == SIGNALED)
        {
            if (AutoReset)
            {
                EvPtr->Status = NOT_SIGNALED;
            }
            return (OBJ_OK);
        }

        /*==================================
         * If not signaled and timeout = 0
         *=================================*/
        if (Timeout == 0)
        {
            return (OBJ_TIMEOUT);
        }

        /*==============================================================
         * If not signaled and timeout, wait signaled or timeout
         *=============================================================*/
        if (Timeout == OS_WAIT_FOREVER)
        {
            lld_wait_on_q (&(EvPtr->WaitQ));
            i = Timeout;                        /* Any non zero value */
        }
        else
        {
            i = lld_timeout_wait_on_q (&(EvPtr->WaitQ), Timeout);
        }
        if (i == 0)
        {
            return (OBJ_TIMEOUT);
        }
        if (lld_os_signal_detected())
        {
            *TimeLeft = i;
            return (OBJ_SIGNAL_RCV);
        }
        if (Timeout != OS_WAIT_FOREVER)
        {
            Timeout = i;
        }
    }
}

/*^^***************************************************************************
 * static DS_U32 EventSet (DS_U32 EvntId)
 *
 * Description: Set event state to signaled
 *
 * Entry :  EvntId   = Returned by EventCreate
 *
 * Return:  OBJ_OK          Operation completed
 *          OBJ_INVALID_ID  Invalid ev id or process does not own ev
 *
 * Notes:   
 *
 **************************************************************************^^*/
static DS_U32 EventSet (DS_U32 EvntId)
{
    EVNT_STR *EvPtr;

    EvPtr = GetEvPtr(EvntId, NULL);
    if (EvPtr == NULL)
    {
        return (OBJ_INVALID_ID);
    }
    if (EvPtr->Status == NOT_SIGNALED)
    {
        EvPtr->Status = SIGNALED;
        lld_wakeup_wait_q (&(EvPtr->WaitQ));
    }
    return (OBJ_OK);
}

/*^^***************************************************************************
 * static DS_U32 EventReset (DS_U32 EvntId)
 *
 * Description: Set event to not signaled state
 *
 * Entry :  EvntId   = Returned by EventCreate
 *
 * Return:  OBJ_OK          Operation completed
 *          OBJ_INVALID_ID  Invalid ev id or process does not own ev
 *
 * Notes:   
 *
 **************************************************************************^^*/
static DS_U32 EventReset (DS_U32 EvntId)
{
    EVNT_STR *EvPtr;

    EvPtr = GetEvPtr(EvntId, NULL);
    if (EvPtr == NULL)
    {
        return (OBJ_INVALID_ID);
    }
    EvPtr->Status = NOT_SIGNALED;
    return (OBJ_OK);
}

/*^^***************************************************************************
 * static DS_U32 EventDelete (DS_U32 EvntId)
 * 
 * Description: Deletes an event.
 *
 * Entry :  EvntId   = Returned by EventCreate
 *
 * Return:  OBJ_OK              Operation completed
 *          OBJ_INVALID_ID      Invalid ev id or process does not own ev
 *
 * Notes:   The event will be deleted only if its reference count is 0.
 *          All tasks waiting on the event will be unblocked with error
 *          return code.
 *          The only caveat here is:
 *          If a taskA deletes a event while other task(s) are pending or
 *          already locked it, and TaskA then creates another event before
 *          the other tasks gets notified of the deleted event, it is
 *          possible that the returned EvntId will be the same as the just
 *          deleted event and hence other pending task(s) will continue to 
 *          run normally.
 *
 **************************************************************************^^*/
static DS_U32 EventDelete (DS_U32 EvntId)
{
    DS_U32 i, j;
    EVNT_STR *EvPtr;

    EvPtr = GetEvPtr(EvntId, &j);
    if (EvPtr == NULL)
    {
        return (OBJ_INVALID_ID);
    }

    /*======================================
     * Remove process from owners list
     *=====================================*/
    EvPtr->OwnerPid[j] = INVALID_PID;

    /*==================================================
     * Check if other process still use the event
     *=================================================*/
    j = 0;
    for (i=0; i<MAX_NOF_PROCS; i++)
    {
        if (EvPtr->OwnerPid[i] != INVALID_PID)
        {
            j = 1;                          /* Other process is using it */
            break;
        }
    }

    /*================================================
     * If no other process is using the event
     *===============================================*/
    if (j == 0)
    {
        EvPtr->Status = UNUSED_EVENT;
    }

    /*======================================
     * Awake all tasks waiting on the ev
     *=====================================*/
    lld_wakeup_wait_q (&(EvPtr->WaitQ));
    return (OBJ_OK);
}

/*^^***************************************************************************
 * static DS_U32 EventInfo (DS_U32 EvntId, DS_U32 *Size, void *Dest)
 * 
 * Description: Return a copy of kernel structure for a event.
 *
 * Entry :  EvntId   = User mode ev ID
 *          Size    = Pointer to receive size of ev structure
 *          Dest    = Area to copy ev info to
 *
 * Return:  
 *
 * Notes:   This fucntion is provided for diagnostic purpose only.
 *
 **************************************************************************^^*/
static DS_U32 EventInfo (DS_U32 EvntId, DS_U32 *Size, void *Dest)
{
    EVNT_STR *EvPtr;

    EvntId--;
    if ((EvntId >= MAX_NOF_EVENTS) || (EventsPtr == NULL))
    {
        return (OBJ_INVALID_ID);
    }
    EvPtr = EventPtr(EvntId);
    *Size = sizeof (EVNT_STR);
    lld_os_copy_to_user(Dest, (DS_S8 *)EvPtr, sizeof(EVNT_STR));
    return (OBJ_OK);
}

/*^^***************************************************************************
 * static EVNT_STR *GetEvPtr (DS_U32 EvntId, DS_U32 *ProcIndex)
 * 
 * Description: Find event corresponding to a ev ID and process ID
 *
 * Entry :  EvntId       = User mode ev ID
 *          ProcIndex   = Ptr to receive process index in OwnerPid array or
 *                        NULL if not needed
 *
 * Return:  Pointer to event struc or NULL
 *
 * Notes:   This call will fail if the event does not exist or if
 *          the caller process did not create the event.
 *
 **************************************************************************^^*/
static EVNT_STR *GetEvPtr (DS_U32 EvntId, DS_U32 *ProcIndex)
{
    EVNT_STR *EvPtr;
    DS_U32  i, ProcId;

    EvntId--;
    if ((EvntId >= MAX_NOF_EVENTS) || (EventsPtr == NULL))
    {
        return (NULL);
    }
    ProcId = mCurrentPid;                  /* Current process ID */
    EvPtr = EventPtr(EvntId);
    if (EvPtr->Status == UNUSED_EVENT)
    {
        return (NULL);
    }
    for (i=0; i<MAX_NOF_PROCS; i++)
    {
        if (EvPtr->OwnerPid[i] == ProcId)
        {
            if (ProcIndex != NULL)
            {
                *ProcIndex = i;
            }
            return (EvPtr);
        }
    }
    return (NULL);
}