Intel Extensible Firmware Interface Manual

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Extensible Firmware Interface Specification

56 12/12/00 Version 1.02

Device Handle

First Handle

GUID

Interface

GUID

Interface

GUID

Interface

GUID

Interface

Protocol

Interface

Instance

Data

Protocol

Interface

Instance

Data

Protocol

Interface

Instance

Data

Protocol

Interface

Instance

Data

Device Handle

GUID

Interface

GUID

Interface

Protocol

Interface

Instance

Data

Protocol

Interface

Instance

Data

...

Figure 3-1. Device Handle to Protocol Handler Mapping

The ability to add new protocol interfaces as new handles or to layer them on existing interfaces

provides great flexibility. Layering makes it possible to add a new protocol that builds on a

device’s basic protocols. An example of this might be to layer on a SIMPLE_TEXT_OUTPUT

protocol support that would build on the handle’s underlying SERIAL_IO protocol.

The ability to add new handles can be used to generate new devices as they are found, or even to

generate abstract devices. An example of this might be to add a multiplexing device that replaces

ConsoleOut with a virtual device that multiplexes the SIMPLE_TEXT_OUTPUT protocol onto

multiple underlying device handles.