Intel Extensible Firmware Interface - Manual (Page 546)

Extensible Firmware Interface Specification
14-6 12/01/02 Version 1.10
EFI_USB_HC_PROTOCOL.GetState()
Summary
Retrieves current state of the USB host controller.
Prototype
typedef
EFI_STATUS
(EFIAPI *EFI_USB_HC_PROTOCOL_GET_STATE) (
IN EFI_USB_HC_PROTOCOL
*This,
OUT EFI_USB_HC_STATE *State
);
Parameters
This A pointer to the EFI_USB_HC_PROTOCOL instance. Type
EFI_USB_HC_PROTOCOL is defined in Section 14.1.
State A pointer to the EFI_USB_HC_STATE data structure that
indicates current state of the USB host controller. Type
EFI_USB_HC_STATE is defined in “Related Definitions.”
Related Definitions
typedef enum {
EfiUsbHcStateHalt,
EfiUsbHcStateOperational,
EfiUsbHcStateSuspend,
EfiUsbHcStateMaximum
} EFI_USB_HC_STATE;
EfiUsbHcStateHalt
The host controller is in halt state. No USB transactions can occur while in this state.
The host controller can enter this state for three reasons:
1. After host controller hardware reset.
2. Explicitly set by software.
3. Triggered by a fatal error such as consistency check failure.
EfiUsbHcStateOperational
The host controller is in an operational state. When in this state, the host controller can
execute bus traffic. This state must be explicitly set to enable the USB bus traffic.
EfiUsbHcStateSuspend
The host controller is in the suspend state. No USB transactions can occur while in this
state. The host controller enters this state for the following reasons:
1. Explicitly set by software.
2. Triggered when there is no bus traffic for 3 microseconds.