// We do nothing special here, just let the PDO handle it
        IoCopyCurrentIrpStackLocationToNext(Irp);
        PoStartNextPowerIrp(Irp);
        ntStatus = PoCallDriver(deviceExtension->TopOfStackDeviceObject,
                                Irp);


        IsoUsb_DecrementIoCount(DeviceObject);

        break; /* IRP_MN_QUERY_POWER */

    default:

        ISOUSB_KdPrint( DBGLVL_MEDIUM,("IsoUsb_ProcessPowerIrp() UNKNOWN POWER MESSAGE (%x)\n", irpStack->MinorFunction));

        //
        // All unhandled power messages are passed on to the PDO
        //

        IoCopyCurrentIrpStackLocationToNext(Irp);
        PoStartNextPowerIrp(Irp);
        ntStatus = PoCallDriver(deviceExtension->TopOfStackDeviceObject, Irp);

        IsoUsb_DecrementIoCount(DeviceObject);

    } /* irpStack->MinorFunction */

    ISOUSB_KdPrint( DBGLVL_MEDIUM,  ( "Exit IsoUsb_ProcessPowerIrp()  ntStatus = 0x%x\n", ntStatus ) );
    return ntStatus;
}


NTSTATUS
IsoUsb_PoRequestCompletion(
    IN PDEVICE_OBJECT       DeviceObject,
    IN UCHAR                MinorFunction,
    IN POWER_STATE          PowerState,
    IN PVOID                Context,
    IN PIO_STATUS_BLOCK     IoStatus
    )
/*++

Routine Description:

	This is the completion routine set in a call to PoRequestPowerIrp()
	that was made in IsoUsb_ProcessPowerIrp() in response to receiving
    an IRP_MN_SET_POWER of type 'SystemPowerState' when the device was
	not in a compatible device power state. In this case, a pointer to
	the IRP_MN_SET_POWER Irp is saved into the FDO device extension 
	(deviceExtension->PowerIrp), and then a call must be
	made to PoRequestPowerIrp() to put the device into a proper power state,
	and this routine is set as the completion routine.

    We decrement our pending io count and pass the saved IRP_MN_SET_POWER Irp
	on to the next driver

Arguments:

    DeviceObject - Pointer to the device object for the class device.
        Note that we must get our own device object from the Context

    Context - Driver defined context, in this case our own functional device object ( FDO )

Return Value:

    The function value is the final status from the operation.

--*/
{
    PIRP irp;
    PDEVICE_EXTENSION deviceExtension;
    PDEVICE_OBJECT deviceObject = Context;
    NTSTATUS ntStatus;

    deviceExtension = deviceObject->DeviceExtension;

	// Get the Irp we saved for later processing in IsoUsb_ProcessPowerIrp()
	// when we decided to request the Power Irp that this routine 
	// is the completion routine for.
    irp = deviceExtension->PowerIrp;

	// We will return the status set by the PDO for the power request we're completing
    ntStatus = IoStatus->Status;

    ISOUSB_KdPrint( DBGLVL_HIGH,("Enter IsoUsb_PoRequestCompletion()\n"));

    // we should not be in the midst of handling a self-generated power irp
    ISOUSB_ASSERT( !deviceExtension->SelfPowerIrp );

    // we must pass down to the next driver in the stack
    IoCopyCurrentIrpStackLocationToNext(irp);

    // Calling PoStartNextPowerIrp() indicates that the driver is finished
    // with the previous power IRP, if any, and is ready to handle the next power IRP.
    // It must be called for every power IRP.Although power IRPs are completed only once,
    // typically by the lowest-level driver for a device, PoStartNextPowerIrp must be called
    // for every stack location. Drivers must call PoStartNextPowerIrp while the current IRP
    // stack location points to the current driver. Therefore, this routine must be called
    // before IoCompleteRequest, IoSkipCurrentStackLocation, and PoCallDriver.

    PoStartNextPowerIrp(irp);

    // PoCallDriver is used to pass any power IRPs to the PDO instead of IoCallDriver.
    // When passing a power IRP down to a lower-level driver, the caller should use
    // IoSkipCurrentIrpStackLocation or IoCopyCurrentIrpStackLocationToNext to copy the IRP to
    // the next stack location, then call PoCallDriver. Use IoCopyCurrentIrpStackLocationToNext
    // if processing the IRP requires setting a completion routine, or IoSkipCurrentStackLocation
    // if no completion routine is needed.

    PoCallDriver(deviceExtension->TopOfStackDeviceObject,
                 irp);

    IsoUsb_DecrementIoCount(deviceObject);

    ISOUSB_KdPrint( DBGLVL_MEDIUM,("IsoUsb_PoRequestCompletion() Exit IRP_MN_SET_POWER\n"));

    deviceExtension->PowerIrp = NULL;

    return ntStatus;
}




NTSTATUS
IsoUsb_PowerIrp_Complete(
    IN PDEVICE_OBJECT NullDeviceObject,
    IN PIRP Irp,
    IN PVOID Context
    )
/*++

Routine Description:

    This routine is called when An IRP_MN_SET_POWER of type 'DevicePowerState'
    has been received by IsoUsb_ProcessPowerIrp(), and that routine has  determined
        1) the request is for full powerup ( to PowerDeviceD0 ), and
        2) We are not already in that state
    A call is then made to PoRequestPowerIrp() with this routine set as the completion routine.


Arguments:

    DeviceObject - Pointer to the device object for the class device.

    Irp - Irp completed.

    Context - Driver defined context.

Return Value:

    The function value is the final status from the operation.

--*/
{
    NTSTATUS ntStatus = STATUS_SUCCESS;
    PDEVICE_OBJECT deviceObject;
    PIO_STACK_LOCATION irpStack;
    PDEVICE_EXTENSION deviceExtension;

    ISOUSB_KdPrint( DBGLVL_HIGH,("enter IsoUsb_PowerIrp_Complete\n"));

    deviceObject = (PDEVICE_OBJECT) Context;

    deviceExtension = (PDEVICE_EXTENSION) deviceObject->DeviceExtension;

    //  If the lower driver returned PENDING, mark our stack location as pending also.
    if (Irp->PendingReturned) {
        IoMarkIrpPending(Irp);
    }

    irpStack = IoGetCurrentIrpStackLocation (Irp);

    // We can assert that we're a  device powerup-to D0 request,
    // because that was the only type of request we set a completion routine
    // for in the first place
    ISOUSB_ASSERT(irpStack->MajorFunction == IRP_MJ_POWER);
    ISOUSB_ASSERT(irpStack->MinorFunction == IRP_MN_SET_POWER);
    ISOUSB_ASSERT(irpStack->Parameters.Power.Type==DevicePowerState);
    ISOUSB_ASSERT(irpStack->Parameters.Power.State.DeviceState==PowerDeviceD0);

    // Now that we know we've let the lower drivers do what was needed to power up,
    //  we can set our device extension flags accordingly
    deviceExtension->CurrentDevicePowerState = PowerDeviceD0;

    Irp->IoStatus.Status = ntStatus;

    IsoUsb_DecrementIoCount(deviceObject);

    ISOUSB_KdPrint( DBGLVL_MEDIUM,("exit IsoUsb_PowerIrp_Complete Exit IRP_MN_SET_POWER D0 complete\n"));
    return ntStatus;
}



NTSTATUS
IsoUsb_SelfSuspendOrActivate(
    IN PDEVICE_OBJECT DeviceObject,
    IN BOOLEAN fSuspend
    )
/*++

Routine Description:

        Called on IsoUsb_PnPAddDevice() to power down until needed (i.e., till a pipe is actually opened).
        Called on IsoUsb_Create() to power up device to D0 before opening 1st pipe.
        Called on IsoUsb_Close() to power down device if this is the last pipe.

Arguments:

    DeviceObject - Pointer to the device object

    fSuspend; TRUE to Suspend, FALSE to acivate.


Return Value:

    If the operation is not attemtped, SUCCESS is returned.
    If the operation is attemtped, the value is the final status from the operation.

--*/
{
    NTSTATUS ntStatus = STATUS_SUCCESS;

    POWER_STATE PowerState;
    PDEVICE_EXTENSION deviceExtension;


    deviceExtension = DeviceObject->DeviceExtension;
    ISOUSB_KdPrint( DBGLVL_MAXIMUM,("Enter IsoUsb_SelfSuspendOrActivate(),fSuspend = %d\n", fSuspend));


	// Can't accept request if:
    //  1) device is removed, 
    //  2) has never been started, 
    //  3) is stopped,
    //  4) has a remove request pending,
    //  5) has a stop device pending
    if ( !IsoUsb_CanAcceptIoRequests( DeviceObject ) ) {
        ntStatus = STATUS_DELETE_PENDING;
        
		ISOUSB_KdPrint( DBGLVL_MEDIUM,("ABORTING IsoUsb_SelfSuspendOrActivate()\n"));
        return ntStatus;
    }
  

    // don't do anything if any System-generated Device Pnp irps are pending
    if ( NULL != deviceExtension->PowerIrp ) {
        ISOUSB_KdPrint( DBGLVL_MAXIMUM,("Exit IsoUsb_SelfSuspendOrActivate(),refusing on pending deviceExtension->PowerIrp 0x%x\n", deviceExtension->PowerIrp));
        return ntStatus;
    }

    // don't do anything if any self-generated Device Pnp irps are pending
    if ( deviceExtension->SelfPowerIrp ) {
        ISOUSB_KdPrint( DBGLVL_MAXIMUM,("Exit IsoUsb_SelfSuspendOrActivate(),refusing on pending deviceExtension->SelfPowerIrp\n" ));
        return ntStatus;
    }

    // don't auto-suspend if any pipes are open
    if ( fSuspend && ( 0 != deviceExtension->OpenPipeCount ) ) {
        ISOUSB_KdPrint( DBGLVL_MAXIMUM,("Exit IsoUsb_SelfSuspendOrActivate(),refusing to self-suspend on OpenPipeCount %d\n", deviceExtension->OpenPipeCount));
        return ntStatus;
    }

    // don't auto-activate if no pipes are open
    if ( !fSuspend && ( 0 == deviceExtension->OpenPipeCount ) ) {
        ISOUSB_KdPrint( DBGLVL_MAXIMUM,("Exit IsoUsb_SelfSuspendOrActivate(),refusing to self-activate, no pipes open\n"));
        return ntStatus;
    }

    // dont do anything if registry CurrentControlSet\Services\IsoUsb\Parameters\PowerDownLevel
    //  has been set to  zero, PowerDeviceD0 ( 1 ), or a bogus high value
    if ( ( deviceExtension->PowerDownLevel == PowerDeviceD0 ) || 
         ( deviceExtension->PowerDownLevel == PowerDeviceUnspecified)  ||
         ( deviceExtension->PowerDownLevel >= PowerDeviceMaximum ) ) {
        ISOUSB_KdPrint( DBGLVL_MAXIMUM,("Exit IsoUsb_SelfSuspendOrActivate(), refusing on deviceExtension->PowerDownLevel == %d\n", deviceExtension->PowerDownLevel));
        return ntStatus;
    }

    if ( fSuspend )
        PowerState.DeviceState = deviceExtension->PowerDownLevel;
    else
        PowerState.DeviceState = PowerDeviceD0;  // power up all the way; we're probably just about to do some IO

    ntStatus = IsoUsb_SelfRequestPowerIrp( DeviceObject, PowerState );

    ISOUSB_KdPrint( DBGLVL_MAXIMUM,("IsoUsb_SelfSuspendOrActivate() status 0x%x on setting dev state %s\n", ntStatus, ISOUSB_StringForDevState(PowerState.DeviceState ) ));

    return ntStatus;

}


NTSTATUS
IsoUsb_SelfRequestPowerIrp(
    IN PDEVICE_OBJECT DeviceObject,
    IN POWER_STATE PowerState
    )
/*++

Routine Description:

    This routine is called by IsoUsb_SelfSuspendOrActivate() to
    actually make the system request for a powerdown/up to PowerState.
    It first checks to see if we are already in Powerstate and immediately
    returns  SUCCESS with no further processing if so


Arguments:

    DeviceObject - Pointer to the device object

    PowerState. power state requested, e.g PowerDeviceD0.