General Design and Implementation Strategies

To design an effective Windows NT display driver, consider the following suggestions and facts:

• Start with a DDK sample display driver written for a video adapter similar to the adapter for which you are writing the driver. It would probably reduce driver design time to modify one of the existing sample drivers rather than write one from scratch.

• For maximum portability, write as much of the driver as possible using the C language. Use assembly language only when necessary for time-critical operations that are not well supported by video adapter hardware. Coding in assembly, while offering the possibility of optimization, is time-consuming and removes the possibility of portability.

• Use miniport drivers for operations that involve resource management, physical device memory mapping, ensuring that register outputs occur in close proximity, or responding to interrupts. The main purpose of miniport drivers is to handle hardware variations within a family and to minimize display driver hardware-type dependencies.

• The display driver is in the same privileged kernel-mode address space as the rest of the Windows NT Executive. Faults in the display driver will cause GDI and the rest of the system to fault.

• Display drivers (and video miniport drivers) are fully preemptable at any time.

• Both the code and data sections of a display driver are entirely pageable.

• Exported functions must execute the standard Windows NT prolog on entry and the epilog on exit. For more information, see the Win32 SDK.