DriverEntry
DriverEntry是miniport驱动的入口，每个miniport驱动程序都应该实现它。在DriverEntry中应该完成的任务如下：
l 定义一个VIDEO_HW_INITIALIZATION_DATA结构，并将其初始化。初始化的内容包括：miniport驱动程序的其他入口、设备扩展（Device Extension）的大小等等。
VIDEO_HW_INITIALIZATION_DATA hwInitData.
// Zero out structure.
VideoPortZeroMemory(
&hwInitData, sizeof(VIDEO_HW_INITIALIZATION_DATA));
// Specify sizes of structure and extension.
hwInitData.HwInitDataSize = sizeof(VIDEO_HW_INITIALIZATION_DATA);
// Set entry points.
hwInitData.HwFindAdapter = &VirtualFindAdapter;
hwInitData.HwInitialize = &VirtualInitialize;
hwInitData.HwStartIO = &VirtualStartIO;
hwInitData.HwGetPowerState = &VirtualGetPowerState;
hwInitData.HwSetPowerState = &VirtualSetPowerState;
hwInitData.HwLegacyResourceList = NULL;
hwInitData.HwLegacyResourceCount = 0;
// Set device extension size.
hwInitData.HwDeviceExtensionSize = sizeof(HW_DEVICE_EXTENSION);
// Virtual device's interface type is zero.
hwInitData.AdapterInterfaceType = 0;
l 调用VideoPortInitialize函数，将VIDEO_HW_INITIALIZATION_DATA结构的地址指针通知系统。
initializationStatus = VideoPortInitialize(Context1,
Context2,
&hwInitData,
NULL);
l 将VideoPortInitialize的返回值作为DriverEntry函数的返回值，返回调用者。
return initializationStatus;
代码说明：
虚拟显示驱动类似mirror驱动，所以我就在mirror的基础上作了相应的修改；这也是微软建议的实现方法：修改一个现存的显示驱动，减少开发时间。Mirror驱动的miniport实现十分简单，基本上所有函数的都是一个空函数。我对DriverEntry作的修改主要是：为自定义的设备扩展申请存储空间。
hwInitData.HwDeviceExtensionSize = sizeof(HW_DEVICE_EXTENSION);
HW_DEVICE_EXTENSION是我自己定义的一个结构，用于存放帧缓冲区的地址：
//
// Define device extension structure. This is device dependent/private
// information.
//
typedef struct _HW_DEVICE_EXTENSION
{
// Frame buffer
ULONG ulFrameBufferSize;
PVOID pFrameBufferAddr;
}HW_DEVICE_EXTENSION, *PHW_DEVICE_EXTENSION;
DriverEntry完整的代码如下：
ULONG
DriverEntry (
PVOID Context1,
PVOID Context2
)
{
VIDEO_HW_INITIALIZATION_DATA hwInitData;
ULONG initializationStatus;
VideoDebugPrint((0, "Virtualed Driver VideoPort [Driver Entry]\n"));
// Zero out structure.
VideoPortZeroMemory(&hwInitData, sizeof(VIDEO_HW_INITIALIZATION_DATA));
// Specify sizes of structure and extension.
hwInitData.HwInitDataSize = sizeof(VIDEO_HW_INITIALIZATION_DATA);
// Set entry points.
hwInitData.HwFindAdapter = &VirtualFindAdapter;
hwInitData.HwInitialize = &VirtualInitialize;
hwInitData.HwStartIO = &VirtualStartIO;
hwInitData.HwGetPowerState = &VirtualGetPowerState;
hwInitData.HwSetPowerState = &VirtualSetPowerState;
hwInitData.HwLegacyResourceList = NULL;
hwInitData.HwLegacyResourceCount = 0;
// Set device extension size.
hwInitData.HwDeviceExtensionSize = sizeof(HW_DEVICE_EXTENSION);
// Virtual device's interface type is zero.
hwInitData.AdapterInterfaceType = 0;
initializationStatus = VideoPortInitialize(Context1,
Context2,
&hwInitData,
NULL);
return initializationStatus;
} // end DriverEntry()