A DirectX 8.0 display driver's source code must include the d3d8.h header file. The header files d3d8caps.h and d3d8types.h are included in d3d8.h.
The DirectX 8.0 Driver Development Kit (DDK) introduces a new DDI-only header file called d3dhalex.h. This header file contains optional helper definitions and macros. Currently, this header contains some macros to assist with reporting D3DCAPS8 to the runtime.