//
    // need 2 decrements
    //

    SSDbgPrint(3, ("HandleRemoveDevice::"));
    requestCount = SSIoDecrement(deviceExtension);

    ASSERT(requestCount > 0);

    SSDbgPrint(3, ("HandleRemoveDevice::"));
    requestCount = SSIoDecrement(deviceExtension);

    KeWaitForSingleObject(&deviceExtension->RemoveEvent, 
                          Executive, 
                          KernelMode, 
                          FALSE, 
                          NULL);

    ReleaseMemory(DeviceObject);

    //
    // We need to send the remove down the stack before we detach,
    // but we don't need to wait for the completion of this operation
    // (and to register a completion routine).
    //

    Irp->IoStatus.Status = STATUS_SUCCESS;
    Irp->IoStatus.Information = 0;

    IoSkipCurrentIrpStackLocation(Irp);
    ntStatus = IoCallDriver(deviceExtension->TopOfStackDeviceObject, Irp);
    
    //
    // Detach the FDO from the device stack
    //
    IoDetachDevice(deviceExtension->TopOfStackDeviceObject);
    IoDeleteDevice(DeviceObject);

    SSDbgPrint(3, ("HandleRemoveDevice - ends\n"));

    return ntStatus;
}

NTSTATUS
HandleQueryCapabilities(
    IN PDEVICE_OBJECT DeviceObject,
    IN PIRP           Irp
    )
/*++

Routine Description:

    This routine services Irp of minor type IRP_MN_QUERY_CAPABILITIES

Arguments:

    DeviceObject - pointer to device object
    Irp - I/O request packet sent by the pnp manager.

Return Value:

    NT status value  

--*/
{
    ULONG                i;
    KEVENT               event;
    NTSTATUS             ntStatus;
    PDEVICE_EXTENSION    deviceExtension;
    PDEVICE_CAPABILITIES pdc;
    PIO_STACK_LOCATION   irpStack;

    SSDbgPrint(3, ("HandleQueryCapabilities - begins\n"));

    //
    // initialize variables
    //

    irpStack = IoGetCurrentIrpStackLocation(Irp);
    deviceExtension = (PDEVICE_EXTENSION) DeviceObject->DeviceExtension;
    pdc = irpStack->Parameters.DeviceCapabilities.Capabilities;

    //
    // We will provide here an example of an IRP that is processed
    // both on its way down and on its way up: there might be no need for
    // a function driver process this Irp (the bus driver will do that).
    // The driver will wait for the lower drivers (the bus driver among 
    // them) to process this IRP, then it processes it again.
    //

    if(pdc->Version < 1 || pdc->Size < sizeof(DEVICE_CAPABILITIES)) {
        
        SSDbgPrint(1, ("HandleQueryCapabilities::request failed\n"));
        ntStatus = STATUS_UNSUCCESSFUL;
        return ntStatus;
    }

    //
    // Set some values in deviceCapabilities here...
    //
    //.............................................
    //
    //
    // Prepare to pass the IRP down
    //

    KeInitializeEvent(&event, NotificationEvent, FALSE);
        
    IoCopyCurrentIrpStackLocationToNext(Irp);
    IoSetCompletionRoutine(Irp, 
                           (PIO_COMPLETION_ROUTINE)IrpCompletionRoutine, 
                           (PVOID)&event, 
                           TRUE, 
                           TRUE, 
                           TRUE);
    ntStatus = IoCallDriver(deviceExtension->TopOfStackDeviceObject, Irp);

    if(ntStatus == STATUS_PENDING) {

        KeWaitForSingleObject(&event, 
                              Executive, 
                              KernelMode, 
                              FALSE, 
                              NULL);
        ntStatus = Irp->IoStatus.Status;
    }

    //
    // initialize PowerDownLevel to disabled
    //

    deviceExtension->PowerDownLevel = PowerDeviceUnspecified;

    //
    // Lower drivers have finished their operation, so now
    // we can finish ours. 
    //

    if(NT_SUCCESS(ntStatus)) {

        deviceExtension->DeviceCapabilities = *pdc;
       
        for(i = PowerSystemSleeping1; i <= PowerSystemSleeping3; i++) {

            if(deviceExtension->DeviceCapabilities.DeviceState[i] < 
                                                            PowerDeviceD3) {

                deviceExtension->PowerDownLevel = 
                    deviceExtension->DeviceCapabilities.DeviceState[i];
            }
        }

        //
        // since its safe to surprise-remove this device, we shall
        // set the SurpriseRemoveOK flag to supress any dialog to 
        // user.
        //

        pdc->SurpriseRemovalOK = 1;

    }

    if(deviceExtension->PowerDownLevel == PowerDeviceUnspecified ||
       deviceExtension->PowerDownLevel <= PowerDeviceD0) {
    
        deviceExtension->PowerDownLevel = PowerDeviceD2;
    }

    SSDbgPrint(3, ("HandleQueryCapabilities - ends\n"));

    return ntStatus;
}


VOID
DpcRoutine(
    IN PKDPC Dpc,
    IN PVOID DeferredContext,
    IN PVOID SystemArgument1,
    IN PVOID SystemArgument2
    )
/*++
 
Routine Description:

    DPC routine triggered by the timer to check the idle state
    of the device and submit an idle request for the device.

Arguments:

    DeferredContext - context for the dpc routine.
                      DeviceObject in our case.

Return Value:

    None

--*/
{
    NTSTATUS          ntStatus;
    PDEVICE_OBJECT    deviceObject;
    PDEVICE_EXTENSION deviceExtension;
    PIO_WORKITEM      item;

    deviceObject = (PDEVICE_OBJECT)DeferredContext;
    deviceExtension = (PDEVICE_EXTENSION)deviceObject->DeviceExtension;

    SSDbgPrint(3, ("DpcRoutine - begins\n"));

    //
    // Clear this event since a DPC has been fired!
    //
    KeClearEvent(&deviceExtension->NoDpcWorkItemPendingEvent);

    if(CanDeviceSuspend(deviceExtension)) {

        SSDbgPrint(3, ("Device is Idle\n"));

        item = IoAllocateWorkItem(deviceObject);

        if(item) {

            IoQueueWorkItem(item, 
                            IdleRequestWorkerRoutine,
                            DelayedWorkQueue, 
                            item);

            ntStatus = STATUS_PENDING;

        }
        else {
        
            SSDbgPrint(3, ("Cannot alloc memory for work item\n"));
            
            ntStatus = STATUS_INSUFFICIENT_RESOURCES;

            //
            // signal the NoDpcWorkItemPendingEvent.
            //
            KeSetEvent(&deviceExtension->NoDpcWorkItemPendingEvent,
                       IO_NO_INCREMENT,
                       FALSE);
        }
    }
    else {
        
        SSDbgPrint(3, ("Idle event not signaled\n"));

        //
        // signal the NoDpcWorkItemPendingEvent.
        //
        KeSetEvent(&deviceExtension->NoDpcWorkItemPendingEvent,
                   IO_NO_INCREMENT,
                   FALSE);
    }

    SSDbgPrint(3, ("DpcRoutine - ends\n"));
}    


VOID
IdleRequestWorkerRoutine(
    IN PDEVICE_OBJECT DeviceObject,
    IN PVOID          Context
    )
/*++
 
Routine Description:

    This is the work item fired from the DPC.
    This workitem checks the idle state of the device
    and submits an idle request.

Arguments:

    DeviceObject - pointer to device object
    Context - context for the work item.

Return Value:

    None

--*/
{
    PIRP                   irp;
    NTSTATUS               ntStatus;
    PDEVICE_EXTENSION      deviceExtension;
    PIO_WORKITEM           workItem;

    SSDbgPrint(3, ("IdleRequestWorkerRoutine - begins\n"));

    //
    // initialize variables
    //
    deviceExtension = (PDEVICE_EXTENSION) DeviceObject->DeviceExtension;
    workItem = (PIO_WORKITEM) Context;

    if(CanDeviceSuspend(deviceExtension)) {

        SSDbgPrint(3, ("Device is idle\n"));

        ntStatus = SubmitIdleRequestIrp(deviceExtension);

        if(!NT_SUCCESS(ntStatus)) {

            SSDbgPrint(1, ("SubmitIdleRequestIrp failed\n"));
        }
    }
    else {

        SSDbgPrint(3, ("Device is not idle\n"));
    }

    IoFreeWorkItem(workItem);

    //
    // signal the NoDpcWorkItemPendingEvent.
    //
    KeSetEvent(&deviceExtension->NoDpcWorkItemPendingEvent,
               IO_NO_INCREMENT,
               FALSE);

    SSDbgPrint(3, ("IdleRequestsWorkerRoutine - ends\n"));
}


VOID
ProcessQueuedRequests(
    IN OUT PDEVICE_EXTENSION DeviceExtension
    )
/*++
 
Routine Description:

    Remove and process the entries in the queue. If this routine is called
    when processing IRP_MN_CANCEL_STOP_DEVICE, IRP_MN_CANCEL_REMOVE_DEVICE
    or IRP_MN_START_DEVICE, the requests are passed to the next lower driver.
    If the routine is called when IRP_MN_REMOVE_DEVICE is received, the IRPs
    are complete with STATUS_DELETE_PENDING

Arguments:

    DeviceExtension - pointer to device extension

Return Value:

    None

--*/
{
    KIRQL       oldIrql;
    PIRP        nextIrp,
                cancelledIrp;
    PVOID       cancelRoutine;
    LIST_ENTRY  cancelledIrpList;
    PLIST_ENTRY listEntry;

    SSDbgPrint(3, ("ProcessQueuedRequests - begins\n"));

    //
    // initialize variables
    //

    cancelRoutine = NULL;
    InitializeListHead(&cancelledIrpList);

    //
    // 1.  dequeue the entries in the queue
    // 2.  reset the cancel routine
    // 3.  process them
    // 3a. if the device is active, send them down
    // 3b. else complete with STATUS_DELETE_PENDING
    //

    while(1) {

        KeAcquireSpinLock(&DeviceExtension->QueueLock, &oldIrql);

        if(IsListEmpty(&DeviceExtension->NewRequestsQueue)) {

            KeReleaseSpinLock(&DeviceExtension->QueueLock, oldIrql);
            break;
        }
    
        //
        // Remove a request from the queue
        //

        listEntry = RemoveHeadList(&DeviceExtension->NewRequestsQueue);
        nextIrp = CONTAINING_RECORD(listEntry, IRP, Tail.Overlay.ListEntry);

        //
        // set the cancel routine to NULL
        //

        cancelRoutine = IoSetCancelRoutine(nextIrp, NULL);

        //
        // check if its already cancelled
        //

        if(nextIrp->Cancel) {
            if(cancelRoutine) {

                //
                // the cancel routine for this IRP hasnt been called yet
                // so queue the IRP in the cancelledIrp list and complete
                // after releasing the lock
                //
                
                InsertTailList(&cancelledIrpList, listEntry);
            }
            else {

                //
                // the cancel routine has run
                // it must be waiting to hold the queue lock
                // so initialize the IRPs listEntry
                //

                InitializeListHead(listEntry);
            }

            KeReleaseSpinLock(&DeviceExtension->QueueLock, oldIrql);
        }
        else {

            KeReleaseSpinLock(&DeviceExtension->QueueLock, oldIrql);

            if(FailRequests == DeviceExtension->QueueState) {

                nextIrp->IoStatus.Information = 0;
                nextIrp->IoStatus.Status = STATUS_DELETE_PENDING;
                IoCompleteRequest(nextIrp, IO_NO_INCREMENT);
            }
            else {

                PIO_STACK_LOCATION irpStack;

                SSDbgPrint(3, ("ProcessQueuedRequests::"));
                SSIoIncrement(DeviceExtension);

                IoSkipCurrentIrpStackLocation(nextIrp);
                IoCallDriver(DeviceExtension->TopOfStackDeviceObject, nextIrp);
               
                SSDbgPrint(3, ("ProcessQueuedRequests::"));
                SSIoDecrement(DeviceExtension);
            }
        }
    } // while loop

    //
    // walk through the cancelledIrp list and cancel them
    //

    while(!IsListEmpty(&cancelledIrpList)) {

        PLIST_ENTRY listEntry = RemoveHeadList(&cancelledIrpList);
        
        cancelledIrp = CONTAINING_RECORD(listEntry, IRP, Tail.Overlay.ListEntry);

        cancelledIrp->IoStatus.Status = STATUS_CANCELLED;
        cancelledIrp->IoStatus.Information = 0;

        IoCompleteRequest(cancelledIrp, IO_NO_INCREMENT);
    }

    SSDbgPrint(3, ("ProcessQueuedRequests - ends\n"));

    return;
}


NTSTATUS
SS_DispatchClean(
    IN PDEVICE_OBJECT DeviceObject,
    IN PIRP           Irp
    )
/*++
 
Routine Description:

    Dispatch routine for IRP_MJ_CLEANUP

Arguments:

    DeviceObject - pointer to device object
    Irp - I/O request packet sent by the pnp manager

Return Value:

    NT status value

--*/
{
    PDEVICE_EXTENSION  deviceExtension;
    KIRQL              oldIrql;
    LIST_ENTRY         cleanupList;
    PLIST_ENTRY        thisEntry, 
                       nextEntry, 
                       listHead;
    PIRP               pendingIrp;
    PIO_STACK_LOCATION pendingIrpStack, 
                       irpStack;
    NTSTATUS           ntStatus;

    //
    // initialize variables
    //

    deviceExtension = (PDEVICE_EXTENSION) DeviceObject->DeviceExtension;
    irpStack = IoGetCurrentIrpStackLocation(Irp);
    InitializeListHead(&cleanupList);