如何获取PPC当前的背光状态?

http://blog.csdn.net/fumingxia19/archive/2007/04/18/1569643.aspx
这里有讲不通过注册表获取和设置背光等级,但为什么我在多普达手机上实验的时候
int GetBackLightLevel()
{
            int iRet = -1;
            DWORD dwOut,dwRet;

            HANDLE h = CreateFile(TEXT("BKL1:"), GENERIC_READ|GENERIC_WRITE, 0,0,
                                                    OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL, 0); 
           if (h != INVALID_HANDLE_VALUE)
          {
                     if ( DeviceIoControl(h, 1 , 0, 0, &dwOut, sizeof(DWORD), &dwRet, 0))
                     {
                                iRet = dwOut;
                     }
                    CloseHandle(h);
          }
          return iRet;
} 

 DeviceIoControl不成功呢,GetLastError=32

谁帮我解决下.

补充：移动开发 ,  Windows Phone