## Graphics Adapter Device Driver Reference

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### Video Manager Interface (VMI)

The VMAN component relies on a special protocol, called the Video Manager Interface (VMI), to receive requests from the translation layers. VMI consists of a small set of operations, each identified by a unique function number. Separate function numbers are required for each operation because VMAN exports only one entry point for the translation layers to communicate with VMAN. This exported function is called VMIEntry. VMIEntry expects four parameters from each function call it receives from a translation layer.

Because the VMIEntry function receives many different types of requests from the translation layers, the gid provides an ID number that identifies the GRADD to receive the operation and the ulFunction provides a function number that identifies the requested operation. The last two parameters ( pIn, pOut) pointer to input and output data structures that are unique to each VMI function.

Most of the requests VMAN receives from a translation layer are passed directly to the appropriate GRADD. Each GRADD has its own exported function , called HWEntry, which is the same function type as VMIEntry (see Graphics Adapter Device Drivers for more information about GHI protocol).