Intel Extensible Firmware Interface - Manual (Page 61)

Overview
Version 1.10 12/01/02 2-21
OM13149
Image Handle
Optional
Optional
Optional
EFI_LOADED_IMAGE_PROTOCOL
EFI_DRIVER_BINDING_PROTOCOL
EFI_DRIVER_CONFIGURATION_PROTOCOL
EFI_DRIVER_DIAGNOSTICS_PROTOCOL
EFI_COMPONENT_NAME_PROTOCOL
Figure 2-8. Driver Image Handle
2.5.3 Host Bus Controllers
Drivers are not allowed to touch any hardware in the driver’s entry point. As a result, drivers will
be loaded and started, but they will all be waiting to be told to manage one or more controllers in
the system. A platform component, like the EFI Boot Manager, is responsible for managing the
connection of drivers to controllers. However, before even the first connection can be made, there
has to be some initial collection of controllers for the drivers to manage. This initial collection of
controllers is known as the Host Bus Controllers. The I/Oabstractions that the Host Bus
Controllers provide are produced by firmware components that are outside the scope of the EFI
Driver Model. The device handles for the Host Bus Controllers and the I/Oabstraction for each
one must be produced by the core firmware on the platform, or an EFI Driver that may not follow
the EFI Driver Model. See the PCI Root Bridge I/O Protocol Specification for an example of an
I/Oabstraction for PCI buses.