Overview

The Extensible Firmware Interface (EFI) describes a programmatic interface to the platform. The platform includes the motherboard, chipset, central processing unit (CPU), and other components. EFI allows for pre-operating system (pre-OS) agents. Pre-OS agents are OS loaders, diagnostics, and other applications that the system needs for applications to execute and interoperate, including EFI drivers and applications. EFI represents a pure interface specification against which the drivers and applications interact, and this chapter highlights some of the architectural aspects of the interface. These architectural aspects include a set of objects and interfaces described by the EFI Specification.

The cornerstones for understanding EFI applications and drivers are several EFI concepts that are defined in the EFI 1.1 Specification. Assuming you are new to EFI, the following introduction explains a few of the key EFI concepts in a helpful framework to keep in mind as you study the specification:

• Objects managed by EFI-based firmware - used to manage system state, including I/O devices, memory, and events

• The EFI System Table - the primary data structure with data information tables and function calls to interface with the systems

• Handle database and protocols - the means by which callable interfaces are registered

• EFI images - the executable content format by which code is deployed

• Events - the means by which software can be signaled in response to some other activity

• Device paths - a data structure that describes the hardware location of...