Intel Extensible Firmware Interface - Manual (Page 548)

Extensible Firmware Interface Specification
14-8 12/01/02 Version 1.10
EFI_USB_HC_PROTOCOL.SetState()
Summary
Sets the USB host controller to a specific state.
Prototype
typedef
EFI_STATUS
(EFIAPI *EFI_USB_HC_PROTOCOL_SET_STATE) (
IN EFI_USB_HC_PROTOCOL
*This,
IN 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 Indicates the state of the host controller that will be set. See the
definition and description of the type
EFI_USB_HC_STATE in
the GetState() function description.
Description
This function is used to explicitly set a USB host controller’s state. There are three states defined
for the USB host controller. These are the halt state, the operational state and the suspend state.
Figure 14-1 illustrates the possible state transitions:
OM13170
Halt State Suspend State
Operational State
Figure 14-1. Software Triggered State Transitions of a USB Host Controller
If the state specified by State is not valid, then EFI_INVALID_PARAMETER is returned. If a
device error occurs while attempting to place the USB host controller into the state specified by
State , then EFI_DEVICE_ERROR is returned. If the USB host controller is successfully placed
in the state specified by State , then EFI_SUCCESS is returned.