上述讲了堆理论，可能读者脑袋都已经大了，为此，我们举个简单的例子来详细说明一下驱动程序的开发过程。
例如我们有个USB Mouse设备，设备信息描述如下：
Device Descriptor:
bcdUSB: 0x0100
bDeviceClass: 0x00
bDeviceSubClass: 0x00
bDeviceProtocol: 0x00
bMaxPacketSize0: 0x08 (8)
idVendor: 0x05E3 (Genesys Logic Inc.)
idProduct: 0x0001
bcdDevice: 0x0101
iManufacturer: 0x00
iProduct: 0x01
iSerialNumber: 0x00
bNumConfigurations: 0x01
ConnectionStatus: DeviceConnected
Current Config value: 0x01
Device Bus Speed: Low
Device Address: 0x02
Open Pipes: 1
Endpoint Descriptor:
bEndpointAddress: 0x81
Transfer Type: Interrupt
wMaxPacketSize: 0x0003 (3)
bInterval: 0x0A
可以看出上述设备有一个中断PIPE，包的最大值为3。可能有人问上述的值怎么得到的，win2k 的DDK中有个usbview的例程，编译一下，将你的USB设备插到PC机的USB口中，运行usbview.exe即可看得相应的设备信息。
有了这些基本信息，就可以编写USB设备了，首先声明一下，下面的代码取自微软的USB鼠标样本程序，版权归微软所有，此处仅仅借用来描述一下USB鼠标驱动的开发过程，读者如需要引用此代码，需要得到微软的同意。
首先，必须输出USBD要求调用的三个函数，首先到设备插入到USB端口时，USBD会调用USBDeviceAttach()函数，相应的代码如下：
extern "C" BOOL
USBDeviceAttach(
USB_HANDLE hDevice, // USB设备句柄
LPCUSB_FUNCS lpUsbFuncs, // USBDI的函数集合
LPCUSB_INTERFACE lpInterface, // 设备接口描述信息
LPCWSTR szUniqueDriverId, // 设备ID描述字符串。
LPBOOL fAcceptControl, // 返回TRUE，标识我们可以控制此设备， 反之表示不能控制
DWORD dwUnused)
{
*fAcceptControl = FALSE;
// 我们的鼠标设备有特定的描述信息，要检测是否是我们的设备。
if (lpInterface == NULL)
return FALSE;
// 打印相关的USB设备接口描述信息。
DEBUGMSG(ZONE_INIT,(TEXT("USBMouse: DeviceAttach, IF u, #EP:u, Class:u, Sub:u,Prot:u\r\n"), lpInterface->Descriptor.bInterfaceNumber,lpInterface->Descriptor.bNumEndpoints, lpInterface->Descriptor.bInterfaceClass,lpInterface->Descriptor.bInterfaceSubClass,lpInterface->Descriptor.bInterfaceProtocol));
// 初试数据USB鼠标类，产生一个接受USB鼠标数据的线程
CMouse * pMouse = new CMouse(hDevice, lpUsbFuncs, lpInterface);
if (pMouse == NULL)
return FALSE;
if (!pMouse->Initialize())
{
delete pMouse;
return FALSE;
}
// 注册一个监控USB设备事件的回调函数，用于监控USB设备是否已经拔掉。
(*lpUsbFuncs->lpRegisterNotificationRoutine)(hDevice,
USBDeviceNotifications, pMouse);
*fAcceptControl = TRUE;
return TRUE;
}
第二个函数是 USBInstallDriver（）函数，
一些基本定义如下：
const WCHAR gcszRegisterClientDriverId[] = L"RegisterClientDriverID";
const WCHAR gcszRegisterClientSettings[] = L"RegisterClientSettings";
const WCHAR gcszUnRegisterClientDriverId[] = L"UnRegisterClientDriverID";
const WCHAR gcszUnRegisterClientSettings[] = L"UnRegisterClientSettings";
const WCHAR gcszMouseDriverId[] = L"Generic_Sample_Mouse_Driver";
函数接口如下：
extern "C" BOOL
USBInstallDriver(
LPCWSTR szDriverLibFile) // @parm [IN] - Contains client driver DLL name
{
BOOL fRet = FALSE;
HINSTANCE hInst = LoadLibrary(L"USBD.DLL");
// 注册USB设备信息
if(hInst)
{
LPREGISTER_CLIENT_DRIVER_ID pRegisterId = (LPREGISTER_CLIENT_DRIVER_ID)
GetProcAddress(hInst, gcszRegisterClientDriverId);
LPREGISTER_CLIENT_SETTINGS pRegisterSettings =
(LPREGISTER_CLIENT_SETTINGS) GetProcAddress(hInst,
gcszRegisterClientSettings);
if(pRegisterId && pRegisterSettings)
{
USB_DRIVER_SETTINGS DriverSettings;
DriverSettings.dwCount = sizeof(DriverSettings);
// 设置我们的特定的信息。
DriverSettings.dwVendorId = USB_NO_INFO;
DriverSettings.dwProductId = USB_NO_INFO;
DriverSettings.dwReleaseNumber = USB_NO_INFO;
DriverSettings.dwDeviceClass = USB_NO_INFO;
DriverSettings.dwDeviceSubClass = USB_NO_INFO;
DriverSettings.dwDeviceProtocol = USB_NO_INFO;
DriverSettings.dwInterfaceClass = 0x03; // HID
DriverSettings.dwInterfaceSubClass = 0x01; // boot device
DriverSettings.dwInterfaceProtocol = 0x02; // mouse
fRet = (*pRegisterId)(gcszMouseDriverId);
if(fRet)
{
fRet = (*pRegisterSettings)(szDriverLibFile,
gcszMouseDriverId, NULL, &DriverSettings);
if(!fRet)
{
//BUGBUG unregister the Client Driver’s ID
}
}
}
else
{
RETAILMSG(1,(TEXT("!USBMouse: Error getting USBD function pointers\r\n")));
}
FreeLibrary(hInst);
}
return fRet;
}
上述代码主要用于产生USB设备驱动程序需要的注册表信息，需要注意的是：USB设备驱动程序不使用标准的注册表函数，而是使用RegisterClientDriverID（）和RegisterClientSettings来注册相应的设备信息。
另外一个函数是USBUninstallDriver()函数，具体代码如下：
extern "C" BOOL
USBUnInstallDriver()
{
BOOL fRet = FALSE;
HINSTANCE hInst = LoadLibrary(L"USBD.DLL");
if(hInst)
{
LPUN_REGISTER_CLIENT_DRIVER_ID pUnRegisterId =
(LPUN_REGISTER_CLIENT_DRIVER_ID)
GetProcAddress(hInst, gcszUnRegisterClientDriverId);
LPUN_REGISTER_CLIENT_SETTINGS pUnRegisterSettings =
(LPUN_REGISTER_CLIENT_SETTINGS) GetProcAddress(hInst,
gcszUnRegisterClientSettings);
if(pUnRegisterSettings)
{
USB_DRIVER_SETTINGS DriverSettings;
DriverSettings.dwCount = sizeof(DriverSettings);
// 必须填入与注册时相同的信息。
DriverSettings.dwVendorId = USB_NO_INFO;
DriverSettings.dwProductId = USB_NO_INFO;
DriverSettings.dwReleaseNumber = USB_NO_INFO;
DriverSettings.dwDeviceClass = USB_NO_INFO;
DriverSettings.dwDeviceSubClass = USB_NO_INFO;
DriverSettings.dwDeviceProtocol = USB_NO_INFO;
DriverSettings.dwInterfaceClass = 0x03; // HID
DriverSettings.dwInterfaceSubClass = 0x01; // boot device
DriverSettings.dwInterfaceProtocol = 0x02; // mouse
fRet = (*pUnRegisterSettings)(gcszMouseDriverId, NULL,
&DriverSettings);
}
if(pUnRegisterId)
{
BOOL fRetTemp = (*pUnRegisterId)(gcszMouseDriverId);
fRet = fRet ? fRetTemp : fRet;
}
FreeLibrary(hInst);
}
return fRet;
}
此函数主要用于删除USBInstallDriver()时创建的注册表信息，同样的它使用自己的函数接口UnRegisterClientDriverID（）和UnRegisterClientSettings（）来做相应的处理。
另外一个需要处理的注册的监控通知函数USBDeviceNotifications（）：
extern "C" BOOL USBDeviceNotifications(LPVOID lpvNotifyParameter, DWORD dwCode,
LPDWORD * dwInfo1, LPDWORD * dwInfo2, LPDWORD * dwInfo3,
LPDWORD * dwInfo4)
{
CMouse * pMouse = (CMouse *)lpvNotifyParameter;
switch(dwCode)
{
case USB_CLOSE_DEVICE:
//删除相关的资源。
delete pMouse;
return TRUE;
}
return FALSE;
}
USB鼠标的类的定义如下：
class CMouse
{
public:
CMouse::CMouse(USB_HANDLE hDevice, LPCUSB_FUNCS lpUsbFuncs,
LPCUSB_INTERFACE lpInterface);
~CMouse();
BOOL Initialize();
private:
// 传输完毕调用的回调函数
static DWORD CALLBACK MouseTransferCompleteStub(LPVOID lpvNotifyParameter);
// 中断处理函数
static ULONG CALLBACK CMouse::MouseThreadStub(PVOID context);
DWORD MouseTransferComplete();
DWORD MouseThread();
BOOL SubmitInterrupt();
BOOL HandleInterrupt();
BOOL m_fClosing;
BOOL m_fReadyForMouseEvents;
HANDLE m_hEvent;
HANDLE m_hThread;
USB_HANDLE m_hDevice;
USB_PIPE m_hInterruptPipe;
USB_TRANSFER m_hInterruptTransfer;
LPCUSB_FUNCS m_lpUsbFuncs;
LPCUSB_INTERFACE m_pInterface;
BOOL m_fPrevButton1;
BOOL m_fPrevButton2;
BOOL m_fPrevButton3;
// 数据接受缓冲区。
BYTE m_pbDataBuffer[8];
};
具体实现如下：
// 构造函数，初始化时调用
CMouse::CMouse(USB_HANDLE hDevice, LPCUSB_FUNCS lpUsbFuncs,
LPCUSB_INTERFACE lpInterface)
{
m_fClosing = FALSE;
m_fReadyForMouseEvents = FALSE;
m_hEvent = NULL;
m_hThread = NULL;
m_hDevice = hDevice;
m_hInterruptPipe = NULL;
m_hInterruptTransfer = NULL;
m_lpUsbFuncs = lpUsbFuncs;
m_pInterface = lpInterface;
m_fPrevButton1 = FALSE;
m_fPrevButton2 = FALSE;
m_fPrevButton3 = FALSE;
memset(m_pbDataBuffer, 0, sizeof(m_pbDataBuffer));
}
// 析构函数，用于清除申请的资源。
CMouse::~CMouse()
{
// 通知系统去关闭相关的函数接口。
m_fClosing = TRUE;
// Wake up the connection thread again and give it time to die.
if (m_hEvent != NULL)
{
// 通知关闭数据接受线程。
SetEvent(m_hEvent);
if (m_hThread != NULL)
{
DWORD dwWaitReturn;
dwWaitReturn = WaitForSingleObject(m_hThread, 1000);
if (dwWaitReturn != WAIT_OBJECT_0)
{
TerminateThread(m_hThread, DWORD(-1));
}
CloseHandle(m_hThread);
m_hThread = NULL;
}
CloseHandle(m_hEvent);
m_hEvent = NULL;
}
if(m_hInterruptTransfer)
(*m_lpUsbFuncs->lpCloseTransfer)(m_hInterruptTransfer);
if(m_hInterruptPipe)
(*m_lpUsbFuncs->lpClosePipe)(m_hInterruptPipe);
}
// 初始化USB鼠标驱动程序
BOOL CMouse::Initialize()
{
LPCUSB_DEVICE lpDeviceInfo = (*m_lpUsbFuncs->lpGetDeviceInfo)(m_hDevice);
// 检测配置：USB鼠标应该只有一个中断管道
if ((m_pInterface->lpEndpoints[0].Descriptor.bmAttributes & USB_ENDPOINT_TYPE_MASK) != USB_ENDPOINT_TYPE_INTERRUPT)
{
RETAILMSG(1,(TEXT("!USBMouse: EP 0 wrong type (u)!\r\n"),
m_pInterface->lpEndpoints[0].Descriptor.bmAttributes));
return FALSE;
}
DEBUGMSG(ZONE_INIT,(TEXT("USBMouse: EP 0:MaxPacket: u, Interval: u\r\n"),
m_pInterface->lpEndpoints[0].Descriptor.wMaxPacketSize,
m_pInterface->lpEndpoints[0].Descriptor.bInterval));
m_hInterruptPipe = (*m_lpUsbFuncs->lpOpenPipe)(m_hDevice,
&m_pInterface->lpEndpoints[0].Descriptor);
if (m_hInterruptPipe == NULL) {
RETAILMSG(1,(TEXT("Mouse: Error opening interrupt pipe\r\n")));
return (FALSE);
}
m_hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
if (m_hEvent == NULL)
{
RETAILMSG(1,(TEXT("USBMouse: Error on CreateEvent for connect event\r\n")));
return(FALSE);
}
// 创建数据接受线程
m_hThread = CreateThread(0, 0, MouseThreadStub, this, 0, NULL);
if (m_hThread == NULL)
{
RETAILMSG(1,(TEXT("USBMouse: Error on CreateThread\r\n")));
return(FALSE);
}
return(TRUE);
}
// 从USB鼠标设备中读出数据，产生相应的鼠标事件。
BOOL CMouse::SubmitInterrupt()
{
if(m_hInterruptTransfer)
(*m_lpUsbFuncs->lpCloseTransfer)(m_hInterruptTransfer);
// 从USB鼠标PIPE中读数据
m_hInterruptTransfer = (*m_lpUsbFuncs->lpIssueInterruptTransfer)
(m_hInterruptPipe, MouseTransferCompleteStub, this,
USB_IN_TRANSFER | USB_SHORT_TRANSFER_OK, // 表示读数据
min(m_pInterface->lpEndpoints[0].Descriptor.wMaxPacketSize,
sizeof(m_pbDataBuffer)),
m_pbDataBuffer,
NULL);
if (m_hInterruptTransfer == NULL)
{
DEBUGMSG(ZONE_ERROR，（L "!USBMouse: Error in IssueInterruptTransfer\r\n"));
return FALSE;
}
else
{
DEBUGMSG(ZONE_TRANSFER,(L"USBMouse::SubmitInterrupt,Transfer:0xX\r\n",
m_hInterruptTransfer));
}
return TRUE;
}
// 处理鼠标中断传输的数据
BOOL CMouse::HandleInterrupt()
{
DWORD dwError;
DWORD dwBytes;
DWORD dwFlags = 0;
INT dx = (signed char)m_pbDataBuffer[1];
INT dy = (signed char)m_pbDataBuffer[2];
BOOL fButton1 = m_pbDataBuffer[0] & 0x01 ? TRUE : FALSE;
BOOL fButton2 = m_pbDataBuffer[0] & 0x02 ? TRUE : FALSE;
BOOL fButton3 = m_pbDataBuffer[0] & 0x04 ? TRUE : FALSE;
if (!(*m_lpUsbFuncs->lpGetTransferStatus)(m_hInterruptTransfer, &dwBytes,&dwError))
{
DEBUGMSG(ZONE_ERROR,(TEXT("!USBMouse: Error in GetTransferStatus(0xX)\r\n"),
m_hInterruptTransfer));
return FALSE;
}
else
{
DEBUGMSG(ZONE_TRANSFER,(TEXT("USBMouse::HandleInterrupt, hTransfer 0xX complete (u bytes, Error:X)\r\n"),
m_hInterruptTransfer,dwBytes,dwError));
}
if (!SubmitInterrupt())
return FALSE;
if(dwError != USB_NO_ERROR)
{
DEBUGMSG(ZONE_ERROR,(TEXT("!USBMouse: Error 0xX in interrupt transfer\r\n"),dwError));
return TRUE;
}
if(dwBytes < 3)
{
DEBUGMSG(ZONE_ERROR,(TEXT("!USBMouse: Invalid byte cnt u from interrupt transfer\r\n"),dwBytes));
return TRUE;
}
if(dx || dy)
dwFlags |= MOUSEEVENTF_MOVE;
if(fButton1 != m_fPrevButton1)
{
if(fButton1)
dwFlags |= MOUSEEVENTF_LEFTDOWN;
else
dwFlags |= MOUSEEVENTF_LEFTUP;
}
if(fButton2 != m_fPrevButton2)
{
if(fButton2)
dwFlags |= MOUSEEVENTF_RIGHTDOWN;
else
dwFlags |= MOUSEEVENTF_RIGHTUP;
}
if(fButton3 != m_fPrevButton3)
{
if(fButton3)
dwFlags |= MOUSEEVENTF_MIDDLEDOWN;
else
dwFlags |= MOUSEEVENTF_MIDDLEUP;
}
m_fPrevButton1 = fButton1;
m_fPrevButton2 = fButton2;
m_fPrevButton3 = fButton3;
DEBUGMSG(ZONE_EVENTS,
(TEXT("USBMouse event: dx:d, dy:d, dwFlags:0xX (B1:u, B2:u, B3:u)\r\n"),
dx,dy,dwFlags,fButton1,fButton2,fButton3));
// 通知系统产生鼠标事件
if (m_fReadyForMouseEvents)
mouse_event(dwFlags, dx, dy, 0, 0);
else
m_fReadyForMouseEvents = IsAPIReady(SH_WMGR);
return TRUE;
}
DWORD CALLBACK CMouse::MouseTransferCompleteStub(LPVOID lpvNotifyParameter)
{
CMouse * pMouse = (CMouse *)lpvNotifyParameter;
return(pMouse->MouseTransferComplete());
}
// 数据传输完毕回调函数
DWORD CMouse::MouseTransferComplete()
{
if (m_hEvent)
SetEvent(m_hEvent);
return 0;
}
ULONG CALLBACK CMouse::MouseThreadStub(PVOID context)
{
CMouse * pMouse = (CMouse *)context;
return(pMouse->MouseThread());
}
// USB鼠标线程
DWORD CMouse::MouseThread()
{
DEBUGMSG(ZONE_INIT,(TEXT("USBMouse: Worker thread started\r\n")));
SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_HIGHEST);
if (SubmitInterrupt())
{
while (!m_fClosing)
{
WaitForSingleObject(m_hEvent, INFINITE);
if (m_fClosing)
break;
if ((*m_lpUsbFuncs->lpIsTransferComplete)(m_hInterruptTransfer))
{
if (!HandleInterrupt())
break;
}
else
{
RETAILMSG(1,(TEXT("!USBMouse: Event signalled, but transfer not complete\r\n")));
// The only time this should happen is if we get an error on the transfer
ASSERT(m_fClosing || (m_hInterruptTransfer == NULL));
break;
}
}
}
RETAILMSG(1,(TEXT("USBMouse: Worker thread exiting\r\n")));
return(0);
}
看到了没有，其实USB的驱动程序编写就这么简单，类似的其他设备，例如打印机设备，就有Bulk OUT PIPE，需要Bulk传输，那就需要了解一下IssueBulkTransfer（）的应用。当然如果是开发USB Mass Storage Disk的驱动，那就需要了解更多的协议，例如Bulk-Only Transport协议等。
微软的Windows CE.NET的Platform Build中已经带有USB Printer和USB Mass Storage Disk的驱动的源代码了，好好研究一下，你一定回受益非浅的。
参考资料：
1． 微软出版社 <<Windows Ce Device Driver Kit>>
2． <<Universal Serial Bus Specification 1.1>> 来自http:://www.usb.org
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