wavepcistream.cpp

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/********************************************************************************
**    Copyright (c) 1998-2000 Microsoft Corporation. All Rights Reserved.
**
**       Portions Copyright (c) 1998-1999 Intel Corporation
**
********************************************************************************/
 
/* The file wavepcistream.cpp was reviewed by LCA in June 2011 and is acceptable for use by Microsoft. */
 
// Every debug output has "Modulname text"
#define STR_MODULENAME "AC97 Stream: "
 
#include "wavepciminiport.h"
#include "wavepcistream.h"
 
IMP_CMiniportStream_SetFormat(CMiniportWaveICHStream);
IMP_CMiniportStream_QueryInterface(CMiniportWaveICHStream, IMiniportWavePciStream);
 
/*****************************************************************************
 * General Info
 *****************************************************************************
 * To protect the stBDList structure that is used to store mappings, we use a
 * spin lock called MapLock. This spin lock is also acquired when we change
 * the DMA registers. Normally, changes in stBDList and the DMA registers go
 * hand in hand. In case we only want to change the DMA registers, we need
 * to acquire the spin lock!
 */
 
#ifdef _MSC_VER
#pragma code_seg("PAGE")
#endif
/*****************************************************************************
 * CreateMiniportWaveICHStream
 *****************************************************************************
 * Creates a wave miniport stream object for the AC97 audio adapter. This is
 * (nearly) like the macro STD_CREATE_BODY_ from STDUNK.H.
 */
NTSTATUS CreateMiniportWaveICHStream
(
    OUT CMiniportWaveICHStream  **MiniportPCIStream,
    IN  PUNKNOWN                pUnknownOuter,
    _When_((PoolType & NonPagedPoolMustSucceed) != 0,
       __drv_reportError("Must succeed pool allocations are forbidden. "
             "Allocation failures cause a system crash"))
    IN  POOL_TYPE               PoolType
)
{
    PAGED_CODE ();
 
    DOUT (DBG_PRINT, ("[CreateMiniportWaveICHStream]"));
 
    //
    // This is basically like the macro at stdunk with the change that we
    // don't cast to interface unknown but to interface MiniportIchStream.
    //
    *MiniportPCIStream = new (PoolType, PoolTag)
                        CMiniportWaveICHStream (pUnknownOuter);
    if (*MiniportPCIStream)
    {
        (*MiniportPCIStream)->AddRef ();
        return STATUS_SUCCESS;
    }
 
    return STATUS_INSUFFICIENT_RESOURCES;
}
 
 
/*****************************************************************************
 * CMiniportWaveICHStream::~CMiniportWaveICHStream
 *****************************************************************************
 * Destructor
 */
CMiniportWaveICHStream::~CMiniportWaveICHStream ()
{
    PAGED_CODE ();
 
 
    DOUT (DBG_PRINT, ("[CMiniportWaveICHStream::~CMiniportWaveICHStream]"));
 
    //
    // Print information about the scatter gather list.
    //
    DOUT (DBG_DMA, ("Head %d, Tail %d, Entries %d.",
                   stBDList.nHead, stBDList.nTail,
                   stBDList.nBDEntries));
 
    // Release the scatter/gather table.
    BDList_Free();
}
 
 
/*****************************************************************************
 * CMiniportWaveICHStream::Init
 *****************************************************************************
 * This routine initializes the stream object, sets up the BDL, and programs
 * the buffer descriptor list base address register for the pin being
 * initialized.
 */
NTSTATUS CMiniportWaveICHStream::Init_()
{
    PAGED_CODE ();
 
    DOUT (DBG_PRINT, ("[CMiniportWaveICHStream::Init]"));
 
    //
    // The rule here is that we return when we fail without a cleanup.
    // The destructor will relase the allocated memory.
    //
 
    //
    // Initialize the BDL spinlock.
    //
    KeInitializeSpinLock (&MapLock);
 
    //
    // Setup the Buffer Descriptor List (BDL)
    // Allocate 32 entries of 8 bytes (one BDL entry).
    // The pointer is aligned on a 8 byte boundary (that's what we need).
    //
 
    if (!BDList_Alloc())
    {
        DOUT (DBG_ERROR, ("Failed AllocateCommonBuffer!"));
        return STATUS_INSUFFICIENT_RESOURCES;
    }
 
    PPREFETCHOFFSET PreFetchOffset;
    //
    // Query for the new interface "PreFetchOffset" and use
    // function offered there in case the interface is offered.
    //
    if (NT_SUCCESS(PortStream->QueryInterface(IID_IPreFetchOffset, (PVOID *)&PreFetchOffset)))
    {
        // why don't we pad by 32 sample frames
        PreFetchOffset->SetPreFetchOffset(32 * (DataFormat->WaveFormatEx.nChannels * 2));
        PreFetchOffset->Release();
    }
 
    return STATUS_SUCCESS;
}
 
/*****************************************************************************
 * CMiniportWaveICHStream::GetAllocatorFraming
 *****************************************************************************
 * Returns the framing requirements for this device.
 * That is sample size (for one sample) and preferred frame (buffer) size.
 */
STDMETHODIMP_(NTSTATUS) CMiniportWaveICHStream::GetAllocatorFraming
(
    _Out_ PKSALLOCATOR_FRAMING AllocatorFraming
)
{
    PAGED_CODE ();
 
    ULONG SampleSize;
 
    DOUT (DBG_PRINT, ("[CMiniportWaveICHStream::GetAllocatorFraming]"));
 
    //
    // Determine sample size in bytes.  Always number of
    // channels * 2 (because 16-bit).
    //
    SampleSize = DataFormat->WaveFormatEx.nChannels * 2;
 
    //
    // Report the suggested requirements.
    //
    AllocatorFraming->RequirementsFlags =
        KSALLOCATOR_REQUIREMENTF_SYSTEM_MEMORY |
        KSALLOCATOR_REQUIREMENTF_PREFERENCES_ONLY;
    AllocatorFraming->Frames = 8;
 
    //
    // Currently, arbitrarily selecting 10ms as the frame target size.
    //
    //  This value needs to be sample block aligned for AC97 to work correctly.
    //  Assumes 100Hz minimum sample rate (otherwise FrameSize is 0 bytes)
    //
    AllocatorFraming->FrameSize = SampleSize * (DataFormat->WaveFormatEx.nSamplesPerSec / 100);
    AllocatorFraming->FileAlignment = FILE_LONG_ALIGNMENT;
    AllocatorFraming->PoolType = NonPagedPool;
 
    return STATUS_SUCCESS;
}
 
 
 
 
/*****************************************************************************
 * Non paged code begins here
 *****************************************************************************
 */
 
#ifdef _MSC_VER
#pragma code_seg()
#endif
/*****************************************************************************
 * CMiniportWaveICHStream::PowerChangeNotify_
 *****************************************************************************
 * This functions saves and maintains the stream state through power changes.
 */
void CMiniportWaveICHStream::PowerChangeNotify_
(
    IN  POWER_STATE NewState
)
{
    KIRQL       OldIrql;
 
    KeAcquireSpinLock (&MapLock,&OldIrql);
 
    if(NewState.DeviceState == PowerDeviceD0)
    {
        ResetDMA ();
 
        // Restore the remaining DMA registers, that is last valid index
        // only if the index is not pointing to 0. Note that the index is
        // equal to head + entries.
        if (stBDList.nTail)
        {
            WriteReg8 (X_LVI, (UCHAR)((stBDList.nTail - 1) & BDL_MASK));
        }
    }
    else
    {
 
        // Disable interrupts and stop DMA just in case.
        WriteReg8 (X_CR, (UCHAR)0);
 
        // Get current index
       // int nCurrentIndex = (int)ReadReg8 (X_CIV);
    }
 
    KeReleaseSpinLock (&MapLock,OldIrql);
}
 
/*****************************************************************************
 * CMiniportWaveICHStream::SetState
 *****************************************************************************
 * This routine sets/changes the DMA engine state to play, stop, or pause
 */
STDMETHODIMP_(NTSTATUS) CMiniportWaveICHStream::SetState
(
    _In_  KSSTATE State
)
{
    KIRQL OldIrql;
 
    DOUT (DBG_PRINT, ("[CMiniportWaveICHStream::SetState]"));
    DOUT (DBG_STREAM, ("SetState to %d", State));
 
 
    //
    // Start or stop the DMA engine dependent of the state.
    //
    switch (State)
    {
        case KSSTATE_STOP:
            // acquire the mapping spin lock
            KeAcquireSpinLock (&MapLock,&OldIrql);
 
            // Just pause DMA. If we have mappings left in our queue,
            // portcls will call RevokeMappings to destroy them.
            PauseDMA ();
 
            // release the mapping spin lock
            KeReleaseSpinLock (&MapLock,OldIrql);
 
            // Release processed mappings
            ReleaseUsedMappings ();
 
            // Reset the position counters.
            TotalBytesMapped = TotalBytesReleased = 0;
            break;
 
        case KSSTATE_ACQUIRE:
        case KSSTATE_PAUSE:
            // acquire the mapping spin lock
            KeAcquireSpinLock (&MapLock,&OldIrql);
 
            // pause now.
            PauseDMA ();
 
            // release the mapping spin lock
            KeReleaseSpinLock (&MapLock,OldIrql);
 
            // Release processed mappings
            ReleaseUsedMappings ();
 
            break;
 
        case KSSTATE_RUN:
            //
            // Let's rock.
            //
 
 
            // Make sure we are not running already.
            if (DMAEngineState & DMA_ENGINE_ON)
            {
                return STATUS_SUCCESS;
            }
 
            // Release processed mappings.
            ReleaseUsedMappings ();
 
            // Get new mappings.
            GetNewMappings ();
 
            // acquire the mapping spin lock
            KeAcquireSpinLock (&MapLock,&OldIrql);
 
            // Kick DMA again just in case.
            ResumeDMA (DMA_ENGINE_PEND);
 
            // release the mapping spin lock
            KeReleaseSpinLock (&MapLock,OldIrql);
            break;
    }
 
    return STATUS_SUCCESS;
}
 
/*****************************************************************************
 * CMiniportWaveICHStream::Service
 *****************************************************************************
 * This routine is called by the port driver in response to the interrupt
 * service routine requesting service on the stream's service group.
 * Requesting service on the service group results in a DPC being scheduled
 * that calls this routine when it runs.
 */
STDMETHODIMP_(void) CMiniportWaveICHStream::Service (void)
{
 
    DOUT (DBG_PRINT, ("Service"));
 
    // release all mappings
    ReleaseUsedMappings ();
 
    // get new mappings
    GetNewMappings ();
}
 
 
/*****************************************************************************
 * CMiniportWaveICHStream::NormalizePhysicalPosition
 *****************************************************************************
 * Given a physical position based on the actual number of bytes transferred,
 * this function converts the position to a time-based value of 100ns units.
 */
STDMETHODIMP_(NTSTATUS) CMiniportWaveICHStream::NormalizePhysicalPosition
(
    _Inout_ PLONGLONG PhysicalPosition
)
{
    ULONG SampleSize;
 
    DOUT (DBG_PRINT, ("NormalizePhysicalPosition"));
 
    //
    // Determine the sample size in bytes
    //
    SampleSize = DataFormat->WaveFormatEx.nChannels * 2;
 
    //
    // Calculate the time in 100ns steps.
    //
    *PhysicalPosition = (_100NS_UNITS_PER_SECOND / SampleSize *
                         *PhysicalPosition) / CurrentRate;
 
    return STATUS_SUCCESS;
}
 
 
/*****************************************************************************
 * CMiniportWaveICHStream::GetPosition
 *****************************************************************************
 * Gets the stream position. This is a byte count of the current position of
 * a stream running on a particular DMA engine.  We must return a sample
 * accurate count or the MiniportDrv32 wave drift tests (35.2 & 36.2) will fail.
 *
 * The position is the sum of three parts:
 *     1) The total number of bytes in released buffers
 *     2) The position in the current buffer.
 *     3) The total number of bytes in played but not yet released buffers
 */
STDMETHODIMP_(NTSTATUS) CMiniportWaveICHStream::GetPosition
(
    _Out_ PULONGLONG   Position
)
{
    KIRQL   OldIrql;
    UCHAR   nCurrentIndex = 0;
    DWORD   buffPos;
 
    ASSERT (Position);
 
    //
    // Acquire the mapping spin lock.
    //
    KeAcquireSpinLock (&MapLock, &OldIrql);
 
    //
    // Start with TotalBytesReleased (mappings released).
    //
    *Position = TotalBytesReleased;
 
    //
    // If we have entries in the list, we may have buffers that have not been
    // released but have been at least partially played.
    //
    if (DMAEngineState != DMA_ENGINE_OFF)
    {
        nCurrentIndex = GetBuffPos(&buffPos);
 
        //
        // Add in our position in the current buffer
        //
        *Position += buffPos;
 
        //
        // Total any buffers that have been played and not released.
        //
        if (nCurrentIndex != ((stBDList.nHead -1) & BDL_MASK))
        {
            int i = stBDList.nHead;
            while (i != nCurrentIndex)
            {
                *Position += (ULONGLONG)stBDList.pMapData[i].ulBufferLength;
                i = (i + 1) & BDL_MASK;
            }
        }
    }
 
    DOUT (DBG_POSITION, ("[GetPosition] POS: %08x'%08x\n", (DWORD)(*Position >> 32), (DWORD)*Position));
 
    //
    // Release the mapping spin lock.
    //
    KeReleaseSpinLock (&MapLock, OldIrql);
 
 
    return STATUS_SUCCESS;
}
 
 
/*****************************************************************************
 * CMiniportWaveICHStream::RevokeMappings
 *****************************************************************************
 * This routine is used by the port to revoke mappings previously delivered
 * to the miniport stream that have not yet been unmapped.  This would
 * typically be called in response to an I/O cancellation request.
 */
STDMETHODIMP_(NTSTATUS) CMiniportWaveICHStream::RevokeMappings
(
    _In_  PVOID     FirstTag,
    _In_  PVOID     LastTag,
    _Out_ PULONG    MappingsRevoked
)
{
    ASSERT (MappingsRevoked);
 
    KIRQL   OldIrql;
    ULONG   ulOldDMAEngineState;
 
    DOUT (DBG_PRINT, ("[CMiniportWaveICHStream::RevokeMappings]"));
 
    //
    // print information about the scatter gather list.
    //
    DOUT (DBG_DMA, ("Head %d, Tail %d, Entries %d.",
                   stBDList.nHead, stBDList.nTail,
                   stBDList.nBDEntries));
 
    //
    // Start accessing the mappings.
    //
    KeAcquireSpinLock (&MapLock, &OldIrql);
 
    //
    // Save old DMA engine state.
    //
    ulOldDMAEngineState = DMAEngineState;
 
    //
    // First stop the DMA engine so it won't process the next buffer in the
    // scatter gather list which might be one of the revoked buffers.
    //
    PauseDMA ();
 
    //
    // Mark items as revoked
    //
 
    for (intptr_t i = (intptr_t)FirstTag; i != (intptr_t)LastTag; i = (i + 1) & BDL_MASK)
    {
        if (stBDList.pMapData[i].ulState == 1)
        {
            stBDList.pMapData[i].ulState = 2;
            BDList[i].wLength = 0;
            BDList[i].wPolicyBits = 0;
            *MappingsRevoked += 1;
        }
    }
 
    //
    // Just un-pause the DMA engine if it was running before
    //
    ResumeDMA(ulOldDMAEngineState);
 
    //
    // Release the mapping spin lock
    //
    KeReleaseSpinLock (&MapLock, OldIrql);
 
 
    return STATUS_SUCCESS;
}
 
 
/*****************************************************************************
 * CMiniportWaveICHStream::MappingAvailable
 *****************************************************************************
 * This routine is called by the port driver to notify the stream that there
 * are new mappings available.  Note that this is ONLY called after the stream
 * has previously had a GetMapping() call fail due to lack of available
 * mappings.
 */
STDMETHODIMP_(void) CMiniportWaveICHStream::MappingAvailable (void)
{
    DOUT (DBG_PRINT, ("MappingAvailable"));
 
    //
    // Release processed mappings.
    //
    ReleaseUsedMappings ();
 
    //
    // Process the new mappings.
    //
    GetNewMappings ();
}
 
 
/*****************************************************************************
 * CMiniportWaveICHStream::GetNewMappings
 *****************************************************************************
 * This routine is called when new mappings are available from the port driver.
 * The routine places mappings into the input mapping queue. AC97 can handle up
 * to 32 entries (descriptors). We program the DMA registers if we have at least
 * one mapping in the queue. The mapping spin lock must be held when calling
 * this routine.
 */
NTSTATUS CMiniportWaveICHStream::GetNewMappings (void)
{
    KIRQL OldIrql;
 
    NTSTATUS    ntStatus = STATUS_SUCCESS;
    ULONG       ulBytesMapped = 0;
    int         nInsertMappings = 0;
    int         nTail;                  // aut. variable
 
    DOUT (DBG_PRINT, ("[CMiniportWaveICHStream::GetNewMappings]"));
 
    // acquire the mapping spin lock
    KeAcquireSpinLock (&MapLock,&OldIrql);
 
    // detect reentrance
    if(m_inGetMapping) {
        m_inGetMapping = 2;
        KeReleaseSpinLock (&MapLock,OldIrql);
        return STATUS_SUCCESS;
    }
 
#if (DBG)
    if (ReadReg16 (X_SR) & SR_CELV)
    {
        //
        // We starve.  :-(
        //
        DOUT (DBG_DMA, ("[GetNewMappings] We starved ... Head %d, Tail %d, Entries %d.",
                stBDList.nHead, stBDList.nTail, stBDList.nBDEntries));
    }
#endif
 
    //
    // Get available mappings up to the max of 31 that we can hold in the BDL.
    //
    while (stBDList.nBDEntries < (MAX_BDL_ENTRIES - 1))
    {
        //
        // Get the information from the list.
        //
        ULONG               Flags;
        ULONG               ulTag = stBDList.nTail;
        ULONG               ulBufferLength;
        PHYSICAL_ADDRESS    PhysAddr;
        PVOID               VirtAddr;
 
 
        // Release the mapping spin lock
NEW_MAPPINGS_AVAILBLE_MAYBE:
        m_inGetMapping = TRUE;
        KeReleaseSpinLock (&MapLock,OldIrql);
 
        //
        // Try to get the mapping from the port.
        // Here comes the problem: When calling GetMapping or ReleaseMapping we
        // cannot hold our spin lock. So we need to buffer the return values and
        // stick the information into the structure later when we have the spin
        // lock acquired.
        //
        ntStatus = PortStream->GetMapping ((PVOID)ULongToPtr(ulTag),
                                           (PPHYSICAL_ADDRESS)&PhysAddr,
                                           &VirtAddr,
                                           &ulBufferLength,
                                           &Flags);
 
        // Acquire the mapping spin lock
        KeAcquireSpinLock (&MapLock,&OldIrql);
 
        //
        // Quit this loop when we run out of mappings.
        //
        if (!NT_SUCCESS (ntStatus))
        {
            if(m_inGetMapping == 2)
                goto NEW_MAPPINGS_AVAILBLE_MAYBE;
            break;
        }
 
        // Sanity check: The audio stack will not give you data
        // that you cannot handle, but an application could use
        // DirectKS and send bad buffer down.
 
        // One mapping needs to be <0x1FFFF bytes for mono
        // streams on the AC97.
        if (ulBufferLength > 0x1FFFE)
        {
            // That is a little too long. That should never happen.
            DOUT (DBG_ERROR, ("[GetNewMappings] Buffer length too long!"));
            ulBufferLength = 0x1FFFE;
        }
 
        // The AC97 can only handle WORD aligned buffers.
        if (PhysAddr.LowPart & 0x01)
        {
            // we cannot play that! Set the buffer length to 0 so
            // that the HW will skip the buffer.
            DOUT (DBG_WARNING, ("[GetNewMappings] Buffer address unaligned!"));
            ulBufferLength = 0;
        }
 
        // The AC97 cannot handle unaligned mappings with respect
        // to the frame size (eg. 42 bytes on 4ch playback).
        if (ulBufferLength % NumberOfChannels)
        {
            // modify the length (don't play the rest of the bytes)
            DOUT (DBG_WARNING, ("[GetNewMappings] Buffer length unaligned!"));
            ulBufferLength -= ulBufferLength % NumberOfChannels;
        }
 
        //
        // Save the mapping.
        //
        nTail = stBDList.nTail;
        stBDList.pMapData[nTail].ulBufferLength = ulBufferLength;
        stBDList.pMapData[nTail].ulState = 1;
        ulBytesMapped += ulBufferLength;
 
        //
        // Fill in the BDL entry with pointer to physical address and length.
        //
        BDList[nTail].dwPtrToPhyAddress = PhysAddr.LowPart;
        BDList[nTail].wLength = (WORD)(ulBufferLength >> 1);
        BDList[nTail].wPolicyBits = BUP_SET;
 
        //
        // Generate an interrupt when portcls tells us to or roughly every 10ms.
        //
        if (Flags || (ulBytesMapped > (CurrentRate * NumberOfChannels * 2) / 100))
        {
            BDList[nTail].wPolicyBits |= IOC_ENABLE;
            ulBytesMapped = 0;
        }
 
        //
        // Take the new mapping into account.
        //
        stBDList.nTail = (stBDList.nTail + 1) & BDL_MASK;
        stBDList.nBDEntries++;
        TotalBytesMapped += (ULONGLONG)ulBufferLength;
        nInsertMappings++;
 
        //
        // Set last valid index (LVI) register! We need to do this here to avoid inconsistency
        // of the BDList with the HW. Note that we need to release spin locks every time
        // we call into portcls, that means we can be interrupted by ReleaseUsedMappings.
        //
        WriteReg8 (X_LVI, (UCHAR)nTail);
    }
 
    //
    // If there were processed mappings, print out some debug messages and eventually try to
    // restart DMA engine.
    //
    if (nInsertMappings)
    {
        //
        // Print debug information ...
        //
        DOUT (DBG_DMA, ("[GetNewMappings] Got %d mappings.", nInsertMappings));
        DOUT (DBG_DMA, ("[GetNewMappings] Head %d, Tail %d, Entries %d.",
                stBDList.nHead, stBDList.nTail, stBDList.nBDEntries));
 
        if(stBDList.nBDEntries >= 2)
            ResumeDMA (DMA_ENGINE_PAUSE);
    }
 
    // Release the mapping spin lock
    m_inGetMapping = FALSE;
    KeReleaseSpinLock (&MapLock,OldIrql);
 
    return ntStatus;
}
 
 
/*****************************************************************************
 * CMiniportWaveICHStream::ReleaseUsedMappings
 *****************************************************************************
 * This routine unmaps previously mapped memory that the hardware has
 * completed processing on.  This routine is typically called at DPC level
 * from the stream deferred procedure call that results from a stream
 * interrupt. The mapping spin lock must be held when calling this routine.
 */
NTSTATUS CMiniportWaveICHStream::ReleaseUsedMappings (void)
{
    KIRQL OldIrql;
    int   nMappingsReleased = 0;
 
    DOUT (DBG_PRINT, ("[CMiniportWaveICHStream::ReleaseUsedMappings]"));
 
    // acquire the mapping spin lock
    KeAcquireSpinLock (&MapLock,&OldIrql);
 
    //
    // Clean up everything to that index.
    //
    while (stBDList.nBDEntries)
    {
        //
        // Get current index
        //
        int nCurrentIndex = (int)ReadReg8 (X_CIV);
 
        //
        // When CIV is == Head -1 we released all mappings.
        //
        if (nCurrentIndex == ((stBDList.nHead - 1) & BDL_MASK))
        {
           break;
        }
 
        //
        // Check if CIV is between head and tail.
        //
        if (nCurrentIndex < stBDList.nHead)
        {
            //
            // Check for CIV being outside range.
            //
            if ((nCurrentIndex + MAX_BDL_ENTRIES) >=
                (stBDList.nHead + stBDList.nBDEntries))
            {
                DOUT (DBG_ERROR, ("[ReleaseUsedMappings] CIV out of range!"));
                break;
            }
        }
        else
        {
            //
            // Check for CIV being outside range.
            //
            if (nCurrentIndex >= (stBDList.nHead + stBDList.nBDEntries))
            {
                DOUT (DBG_ERROR, ("[ReleaseUsedMappings] CIV out of range!"));
                break;
            }
        }
 
        //
        // Check to see if we've released all the buffers.
        //
        if (stBDList.nHead == nCurrentIndex)
        {
            if (nCurrentIndex == ((stBDList.nTail - 1) & BDL_MASK))
            {
                //
                // A special case is starvation or stop of stream, when the
                // DMA engine finished playing the buffers, CVI is equal LVI
                // and SR_CELV is set.
                //
                if (!(ReadReg16 (X_SR) & SR_CELV))
                {
                    // It is still playing the last buffer.
                    break;
                }
 
                //
                // In case the CVI=LVI bit is set, nBDEntries should be 1
                //
                if (stBDList.nBDEntries != 1)
                {
                    DOUT (DBG_ERROR, ("[ReleaseUsedMappings] Inconsitency: Tail reached and Entries != 1."));
                }
            }
            else
            {
                //
                // Bail out. Current Index did not move.
                //
                break;
            }
        }
 
        //
        // Save the tag and remove the entry from the list.
        //
        ULONG   ulTag = stBDList.nHead;
        stBDList.nBDEntries--;
        stBDList.nHead = (stBDList.nHead + 1) & BDL_MASK;
        nMappingsReleased++;
 
        // if entry has not been revoked
        if(stBDList.pMapData[ulTag].ulState == 1)
        {
            TotalBytesReleased += (ULONGLONG)stBDList.pMapData[ulTag].ulBufferLength;
 
            // Release the mapping spin lock
            KeReleaseSpinLock (&MapLock,OldIrql);
 
            //
            // Release this entry.
            //
            PortStream->ReleaseMapping ((PVOID)ULongToPtr(ulTag));
 
            // acquire the mapping spin lock
            KeAcquireSpinLock (&MapLock,&OldIrql);
        }
 
        stBDList.pMapData[ulTag].ulState = 0;
    }
 
 
    // Print some debug information in case we released mappings.
    if (nMappingsReleased)
    {
        //
        // Print release information and return.
        //
        DOUT (DBG_DMA, ("[ReleaseUsedMappings] Head %d, Tail %d, Entries %d.",
                       stBDList.nHead, stBDList.nTail, stBDList.nBDEntries));
    }
 
    // Release the mapping spin lock
    KeReleaseSpinLock (&MapLock,OldIrql);
 
    return STATUS_SUCCESS;
}
 
/*****************************************************************************
 * Non paged code begins here
 *****************************************************************************
 */
 
#ifdef _MSC_VER
#pragma code_seg()
#endif
 
void CMiniportWaveICHStream::InterruptServiceRoutine()
{
    //
    // Request DPC service for PCM out.
    //
    Miniport->Port->Notify (ServiceGroup);
}