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Figure 7.8: An example of the contents of the DeviceN nested key for the device driver subkey under HKEY_LOCAL_MACHINE\SYSTEM\ControlSetnnn\Services Depending on the video driver implementation | Figure 7.8 An example of the contents of the DeviceV nested key for the device driver subkey under HKEY_LOCAL_MACHINE SYSTEM ControlSetwww Services Depending on the video driver implementation this key may contain a variety of parameters including the VgaCompatible standard setting which is set to FALSE for most modern drivers. If the parameter is set to FALSE the driver is based on the MS VGA miniport driver. The following REG_BINARY settings under the HKEY_LOCAL_MACHINE SYSTEM CurrentControlSet Control Video 56652C39- 3E1C-4A83-AD68-1CF58F0EDEE9 0000 HardwareInformation.AdapterString HardwareInformation.BiosString HardwareInformation.ChipType HardwareInformation.Crc32 HardwareInformation.DacType HardwareInformation.MemorySize contain hardware information displayed by administrative utilities. Notice that similar settings are also present in Windows NT 2000 registries but under different locations. When Windows GUI starts the system reads the video settings contained under the following registry key Fig. 7.9 HKEY_LOCAL_MACHINE SYSTEM CurrentControlSet Hardware Profiles Current System CurrentControlSet Control VIDEO 56652C39-3E1C-4A83-AD68-1CF58F0EDEE9 0000 Figure 7.9 Registry settings that specify the video mode After reading these settings the system checks whether the display driver supporting the specified mode is present. As soon as the appropriate driver has been found the startup procedure continues. What happens though if the system can t find an appropriate driver The answer s simple the system will use standard VGA mode 16 colors . Thus we have considered the usage of the HKEY_LOCAL_MACHINE HARDWARE DEVICEMAP information for searching for specific device driver data. We ve used the video adapter as an example but the system uses a similar algorithm for locating the appropriate drivers for any other device. To summarize let s note that the HKEY_LOCAL_MACHINE HARDWARE DEVICEMAP data describes either an actual port name or the path to the appropriate subkey
