Microsoft KB Archive/200876

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HOWTO: Get Information for a Given Display Driver

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Q200876

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The information in this article applies to:


 * Microsoft Win32 Device Driver Kit (DDK) versions Windows 95, Windows 98

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SUMMARY
This article describes a technique that allows an application to get information about a specified display device on a Windows 95 or Windows 98 system.

MORE INFORMATION
On Windows 98 systems, multiple display devices can coexist on a system. There is no API available that allows you to obtain information about the display devices directly from the system. This articles describes a technique for parsing the registry database to get this information.

The sample code uses the FindDevice function to search for devices with the given Class name. After finding the device, the GetDeviceValue function is used to get the details for the device.

// // Function   : GetDeviceValue // // Purpose    : Read a value from the HW or SW of a PnP device. // // Parameters : //  szHardwareKey    Hardware key for the device. //  szKey            Subkey. //  szValue          The value to be queried. //  buf              Buffer to receive the value. //  cbbuf            Size of buffer. // // Returns    : TRUE if value is obtained. //

BOOL GetDeviceValue(LPCSTR szHardwareKey, LPSTR szKey, LPSTR Value, BYTE *buf, DWORD cbbuf) {   HKEY    hkeyHW; HKEY   hkeySW; BOOL   bFlag = FALSE; DWORD  nSize; char   szSoftwareKey[MAX_PATH]; *(DWORD*)buf = 0; //    // Open the HW key. //    if (RegOpenKey(HKEY_LOCAL_MACHINE, szHardwareKey, &hkeyHW) ==    ERROR_SUCCESS) {       //         // Try to read the value from the HW key. //        *buf = 0; nSize = cbbuf; if (RegQueryValueEx(hkeyHW, szValue, NULL, NULL, buf, &nSize) == ERROR_SUCCESS) {           bFlag = TRUE; }       else {           //             // Now try the SW key. //            static char szSW[] = "System\\CurrentControlSet\\Services\\Class\\"; lstrcpy(szSoftwareKey, szSW); nSize = sizeof(szSoftwareKey) - sizeof(szSW); RegQueryValueEx(hkeyHW, "Driver", NULL, NULL, szSoftwareKey           + sizeof(szSW) - 1, &nSize); if (szKey) {               lstrcat(szSoftwareKey, "\\"); lstrcat(szSoftwareKey, szKey); }           if (RegOpenKey(HKEY_LOCAL_MACHINE, szSoftwareKey, &hkeySW) == ERROR_SUCCESS) {               *buf = 0; nSize = cbbuf; if (RegQueryValueEx(hkeySW, szValue, NULL, NULL, buf, &nSize) == ERROR_SUCCESS) {                   bFlag = TRUE; }               RegCloseKey(hkeySW); }       }        RegCloseKey(hkeyHW); }   return bFlag; }

// // Function  : FindDevice // // Purpose   : Enumerates the started PnP devices looking for a  //              device of a particular class. // // Parameters : // iDeviceNumber   What device to return (0=first device, 1=second, etc.) // szDeviceClass   What class device (for example, "Display"). NULL will //                 match all. // szDeviceID     Buffer to return the hardware ID (MAX_PATH bytes). // // Return    : TRUE if a device was found. // // Example: // //     for (int i=0; FindDevice(i, "Display", DeviceID); i++) //     { //      } //

BOOL FindDevice(int iDeviceNumber, LPCSTR szDeviceClass, LPSTR      szHardwareKey) {   HKEY    hkeyPnP; HKEY   hkey; DWORD  nCounter; DWORD  nSize; DWORD  dwReturnValue; char   szBuffer[MAX_PATH]; if (RegOpenKey(HKEY_DYN_DATA, "Config Manager\\Enum", &hkeyPnP)      !=  ERROR_SUCCESS) return FALSE; for (nCounter=0; RegEnumKey(hkeyPnP, nCounter, szBuffer, sizeof(szBuffer)) == 0; nCounter++) {       static char szHW[] = "Enum\\"; if (RegOpenKey(hkeyPnP, szBuffer, &hkey) != ERROR_SUCCESS) continue; lstrcpy(szHardwareKey, szHW); nSize = MAX_PATH - sizeof(szHW); RegQueryValueEx(hkey, "HardwareKey", NULL, NULL,      (BYTE*)szHardwareKey + sizeof(szHW) - 1, &nSize); dwReturnValue = 0; nSize = sizeof(dwReturnValue); RegQueryValueEx(hkey, "Problem", NULL, NULL,      (BYTE*)&dwReturnValue, &nSize); RegCloseKey(hkey); if (dwReturnValue != 0)       // If this device has a problem, // skip it. continue; if (szDeviceClass) {           GetDeviceValue(szHardwareKey, NULL, "Class", szBuffer,       sizeof(szBuffer)); if (lstrcmpi(szDeviceClass, szBuffer) != 0) continue; }       //         // We found a device, make sure it is the one the caller wants. //        if (iDeviceNumber-- == 0) {           RegCloseKey(hkeyPnP); return TRUE; }   }    RegCloseKey(hkeyPnP); return FALSE; }

void main(int argc, char **argv) {   int      iDeviceCounter; char   szKey[MAX_PATH]; char   szValue[MAX_PATH]; #define GETSZ(a, b) \ GetDeviceValue(szKey, a, b, szValue, sizeof(szValue)); \ printf(" %-20s:\t%s\n", b, szValue); for (iDeviceCounter=0; FindDevice(iDeviceCounter, "Display", szKey);      iDeviceCounter++) {       printf("**** Display %d\n", iDeviceCounter+1); GETSZ(NULL, "DeviceDesc"); GETSZ(NULL, "DriverDesc"); GETSZ(NULL, "DriverDate"); GETSZ(NULL, "ProviderName"); GETSZ(NULL, "Mfg"); GETSZ("DEFAULT", "drv"); GETSZ("DEFAULT", "minivdd"); } }