Intel Extensible Firmware Interface - Manual (Page 604)

Extensible Firmware Interface Specification
14-64 12/01/02 Version 1.10
14.2.6 USB Device Paths
An EFI_USB_IO_PROTOCOL must be installed on a handle for its services to be available to
USB device drivers. In addition to the EFI_USB_IO_PROTOCOL , an EFI_DEVICE_PATH must
also be installed on the same handle. See Chapter 5 for a detailed description of the
EFI_DEVICE_PATH .
14.2.6.1 USB Device Path Node
Below is the definition for USB Device Path Node.
#define MESSAGING_DEVICE_PATH 0x03
#define MSG_USB_DP 0x05
typedef struct _USB_DEVICE_PATH {
EFI_DEVICE_PATH
Header;
UINT8 ParentPortNumber;
UINT8 InterfaceNumber;
} USB_DEVICE_PATH;
Parameters
Header Device Path Header for USB Device Path Node.
ParentPortNumber The parent USB hub port which this controller is connected to.
InterfaceNumber The USB Controller identifier within a USB device. Some USB
device may have several interfaces (i.e. USB Controllers). The
Interface Number is the identifier for the USB Controller.