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Extensible Firmware Interface Specification
14-34 12/01/02 Version 1.10
14.2 USB Driver Model
14.2.1 Scope
These sections (Sections 14.2 and below) describe the USB Driver Model. This includes the
behavior of USB Bus Drivers, the behavior of a USB Device Drivers, and a detailed description of
the EFI USB I/O Protocol. This document provides enough material to implement a USB Bus
Driver, and the tools required to design and implement USB Device Drivers. It does not provide
any information on specific USB devices.
The material contained in this document is designed to extend the EFI Specification and the EFI
Driver Model Specification in a way that supports USB device drivers and USB bus drivers. These
extensions are provided in the form of USB specific protocols. This document provides the
information required to implement a USB Bus Driver in system firmware. The document also
contains the information required by driver writers to design and implement USB Device Drivers
that a platform may need to boot an EFI compliant OS.
A full understanding of the EFI Specification, the EFI Driver Model Specification, and the USB
Specification is assumed throughout this document. The USB Driver Model described here is
intended to be a foundation on which a USB Bus Driver and a wide variety of USB Device Drivers
can be created. The current version of USB Driver Model is designed for USB 1.1; it may not be
compatible newer revisions of USB.
14.2.2 USB Driver Model Overview
The EFI USB Driver Stack includes the USB Bus Driver, USB Host Controller Driver, and
individual USB device drivers.
OM13171
USB Bus Controller Handle
EFI_DEVICE_PATH_PROTOCOL
EFI_XYZ_I/O_PROTOCOL
EFI_USB_HC_PROTOCOL
Figure 14-2. USB Bus Controller Handle