## Physical Device Driver Reference

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### Calling Advanced BIOS Services

For ABIOS device drivers that use the Operating System Transfer Convention, the DevHlp_ABIOSCall, is provided to invoke ABIOS with the correct mode- specific set of parameters. The physical device driver passes the ABIOS request block pointer, its LID, and the ABIOS primary function (start, interrupt, or timeout) to the DevHlp_ABIOSCall. This sets up the stack for the call to ABIOS and calls the ABIOS function.

For ABIOS device drivers that use the ABIOS Transfer Convention, the DevHlp _ABIOSCommonEntry, is provided to invoke the ABIOS Common Entry Points. The physical device driver passes the mode-specific pointer to the ABIOS request block and the ABIOS primary function (common start, common interrupt, or common timeout) to the DevHlp service. The DevHlp service sets up the stack and calls the requested ABIOS common entry point.

Note: The return code of the ABIOS function is in the ABIOS request block.