上述講了堆理論，可能讀者腦袋都已經大了，為此，我們舉個簡單的例子來詳細說明一下驅動程序的開發過程。
例如我們有個USB Mouse設備，設備信息描述如下：
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
可以看出上述設備有一個中斷PIPE，包的最大值為3。可能有人問上述的值怎么得到的，win2k 的DDK中有個usbview的例程，編譯一下，將你的USB設備插到PC機的USB口中，運行usbview.exe即可看得相應的設備信息。
有了這些基本信息，就可以編寫USB設備了，首先聲明一下，下面的代碼取自微軟的USB鼠標樣本程序，版權歸微軟所有，此處僅僅借用來描述一下USB鼠標驅動的開發過程，讀者如需要引用此代碼，需要得到微軟的同意。
首先，必須輸出USBD要求調用的三個函數，首先到設備插入到USB端口時，USBD會調用USBDeviceAttach()函數，相應的代碼如下：
extern "C" BOOL
USBDeviceAttach(
USB_HANDLE hDevice, // USB設備句柄
LPCUSB_FUNCS lpUsbFuncs, // USBDI的函數集合
LPCUSB_INTERFACE lpInterface, // 設備接口描述信息
LPCWSTR szUniqueDriverId, // 設備ID描述字符串。
LPBOOL fAcceptControl, // 返回TRUE，標識我們可以控制此設備， 反之表示不能控制
DWORD dwUnused)
{
*fAcceptControl = FALSE;
// 我們的鼠標設備有特定的描述信息，要檢測是否是我們的設備。
if (lpInterface == NULL)
return FALSE;
// 打印相關的USB設備接口描述信息。
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));
// 初試數據USB鼠標類，產生一個接受USB鼠標數據的線程
CMouse * pMouse = new CMouse(hDevice, lpUsbFuncs, lpInterface);
if (pMouse == NULL)
return FALSE;
if (!pMouse->Initialize())
{
delete pMouse;
return FALSE;
}
// 注冊一個監控USB設備事件的回調函數，用于監控USB設備是否已經拔掉。
(*lpUsbFuncs->lpRegisterNotificationRoutine)(hDevice,
USBDeviceNotifications, pMouse);
*fAcceptControl = TRUE;
return TRUE;
}
第二個函數是 USBInstallDriver（）函數，
一些基本定義如下：
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";
函數接口如下：
extern "C" BOOL
USBInstallDriver(
LPCWSTR szDriverLibFile) // @parm [IN] - Contains client driver DLL name
{
BOOL fRet = FALSE;
HINSTANCE hInst = LoadLibrary(L"USBD.DLL");
// 注冊USB設備信息
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);
// 設置我們的特定的信息。
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;
}
上述代碼主要用于產生USB設備驅動程序需要的注冊表信息，需要注意的是：USB設備驅動程序不使用標準的注冊表函數，而是使用RegisterClientDriverID（）和RegisterClientSettings來注冊相應的設備信息。
另外一個函數是USBUninstallDriver()函數，具體代碼如下：
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);
// 必須填入與注冊時相同的信息。
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;
}
此函數主要用于刪除USBInstallDriver()時創建的注冊表信息，同樣的它使用自己的函數接口UnRegisterClientDriverID（）和UnRegisterClientSettings（）來做相應的處理。
另外一個需要處理的注冊的監控通知函數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:
//刪除相關的資源。
delete pMouse;
return TRUE;
}
return FALSE;
}
USB鼠標的類的定義如下：
class CMouse
{
public:
CMouse::CMouse(USB_HANDLE hDevice, LPCUSB_FUNCS lpUsbFuncs,
LPCUSB_INTERFACE lpInterface);
~CMouse();
BOOL Initialize();
private:
// 傳輸完畢調用的回調函數
static DWORD CALLBACK MouseTransferCompleteStub(LPVOID lpvNotifyParameter);
// 中斷處理函數
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;
// 數據接受緩沖區。
BYTE m_pbDataBuffer[8];
};
具體實現如下：
// 構造函數，初始化時調用
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));
}
// 析構函數，用于清除申請的資源。
CMouse::~CMouse()
{
// 通知系統去關閉相關的函數接口。
m_fClosing = TRUE;
// Wake up the connection thread again and give it time to die.
if (m_hEvent != NULL)
{
// 通知關閉數據接受線程。
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鼠標驅動程序
BOOL CMouse::Initialize()
{
LPCUSB_DEVICE lpDeviceInfo = (*m_lpUsbFuncs->lpGetDeviceInfo)(m_hDevice);
// 檢測配置：USB鼠標應該只有一個中斷管道
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);
}
// 創建數據接受線程
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);
}
// 從USB鼠標設備中讀出數據，產生相應的鼠標事件。
BOOL CMouse::SubmitInterrupt()
{
if(m_hInterruptTransfer)
(*m_lpUsbFuncs->lpCloseTransfer)(m_hInterruptTransfer);
// 從USB鼠標PIPE中讀數據
m_hInterruptTransfer = (*m_lpUsbFuncs->lpIssueInterruptTransfer)
(m_hInterruptPipe, MouseTransferCompleteStub, this,
USB_IN_TRANSFER | USB_SHORT_TRANSFER_OK, // 表示讀數據
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:0x%X\r\n",
m_hInterruptTransfer));
}
return TRUE;
}
// 處理鼠標中斷傳輸的數據
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(0x%X)\r\n"),
m_hInterruptTransfer));
return FALSE;
}
else
{
DEBUGMSG(ZONE_TRANSFER,(TEXT("USBMouse::HandleInterrupt, hTransfer 0x%X 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 0x%X 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:0x%X (B1:%u, B2:%u, B3:%u)\r\n"),
dx,dy,dwFlags,fButton1,fButton2,fButton3));
// 通知系統產生鼠標事件
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());
}
// 數據傳輸完畢回調函數
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鼠標線程
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
到了沒有，其實USB的驅動程序編寫就這么簡單，類似的其他設備，例如打印機設備，就有Bulk OUT
PIPE，需要Bulk傳輸，那就需要了解一下IssueBulkTransfer（）的應用。當然如果是開發USB Mass Storage
Disk的驅動，那就需要了解更多的協議，例如Bulk-Only Transport協議等。
微軟的Windows CE.NET的Platform Build中已經帶有USB Printer和USB Mass Storage Disk的驅動的源代碼了，好好研究一下，你一定回受益非淺的。
參考資料：
1． 微軟出版社 <<Windows Ce Device Driver Kit>>
2． <<Universal Serial Bus Specification 1.1>> 來自http:://www.usb.org