看过sysinternal.com的ctrl2cap键盘过滤驱动的哥们请进！！

NTSTATUS Ctrl2capInit(
    IN PDRIVER_OBJECT DriverObject
    )
{
  ......
  status = IoCreateDevice( DriverObject,
                             sizeof(DEVICE_EXTENSION),
                             NULL,
                             FILE_DEVICE_KEYBOARD,
                             0,
                             FALSE,
                             &device );
 ......
 status = IoAttachDevice( device, &ntUnicodeString, &devExt->TopOfStack );
......

}

//---------------------------------------------------------nastATUS
Ctrl2capAddDevice(
    IN PDRIVER_OBJECT   Driver,
    IN PDEVICE_OBJECT   PDO
    )
{
.......
    status = IoCreateDevice(Driver,                  
                            sizeof(DEVICE_EXTENSION),
                            NULL,                    
                            FILE_DEVICE_KEYBOARD,  
                            0,                    
                            FALSE,                
                            &device              
                            );
.......
    devExt->TopOfStack = IoAttachDeviceToDeviceStack(device, PDO);
.......
}

！！！ 看不懂，为什么还要加Ctrl2capInit这样的函数，这不就两次家了过滤驱动了吗？
  请高手指教！！！！！！！！！！

兄弟可看见下面代码

#if WIN2K
    //
    // Power IRPs are the only ones we have to handle specially under
    // Win2k since they require the special PoCallDriver and
    // PoStartNextPowerIrp function calls.
    //
    DriverObject->MajorFunction [IRP_MJ_POWER]  = Ctrl2capPower;

    //
    // The only reason we need to handle PnP IRPs is to know when
    // a device we\'ve attached to disappears (is removed).
    //
    DriverObject->MajorFunction [IRP_MJ_PNP]  = Ctrl2capPnP;

    //
    // Under Win2K we get told about the presence of keyboard
    // devices through our AddDevice entry point.
    //
    DriverObject->DriverUnload = Ctrl2capUnload;
    DriverObject->DriverExtension->AddDevice = Ctrl2capAddDevice;

    return STATUS_SUCCESS;

#else  // WIN2K

    //
    // Under NT 4 we go out and hook the keyboard class device for
    // keyboard 0.
    //
    return Ctrl2capInit( DriverObject );
#endif // WIN2K
他是用于区别WIN2K和NT的，所以Ctrl2capInit是用语NT4，而Ctrl2capAddDevice用于2000