Intel Extensible Firmware Interface - Manual (Page 253)

Protocols — EFI Driver Model
Version 1.10 12/01/02 9-11
If the driver specified by This is a bus driver, and RemainingDevicePath is NULL , then all
of the children of Controller are discovered and enumerated, and a device handle is created for
each child.
If the driver specified by This is a bus driver that is capable of creating one child handle at a time
and RemainingDevicePath is not NULL , then only the device handle for the child device
specified by RemainingDevicePath is created. Depending on the bus type, all of the child
devices may need to be discovered and enumerated, but only device handle for the one child
specified by
RemainingDevicePath shall be created.
The Start() function is designed to be invoked from the EFI boot service
ConnectController() . As a result, much of the error checking on the parameters to
Start() has been moved into this common boot service. It is legal to call Start() from other
locations, but the following calling restrictions must be followed or the system behavior will not be
deterministic.
1. ControllerHandle must be a valid EFI_HANDLE .
2. If RemainingDevicePath is not NULL , then it must be a pointer to a naturally aligned
EFI_DEVICE_PATH that contains at least one device path node other than the end node.
3. Prior to calling Start() , the Supported() function for the driver specified by This must
have been called with the same calling parameters, and Supported() must have returned
EFI_SUCCESS .
Status Codes Returned
EFI_SUCCESS The device was started .
EFI_DEVICE_ERROR The device could not be started due to a device error.
EFI_OUT_OF_RESOURCES The request could not be completed due to a lack of resources.
Examples
extern EFI_GUID gEfiDriverBindingProtocolGuid;
EFI_HANDLE DriverImageHandle;
EFI_HANDLE ControllerHandle;
EFI_DRIVER_BINDING_PROTOCOL *DriverBinding;
EFI_DEVICE_PATH_PROTOCOL *RemainingDevicePath;
//
// Use the DriverImageHandle to get the Driver Binding Protocol instance
//
Status = gBS->OpenProtocol (
DriverImageHandle,
&gEfiDriverBindingProtocolGuid,
&DriverBinding,
DriverImageHandle,
NULL,
EFI_OPEN_PROTOCOL_GET_PROTOCOL
);
if (EFI_ERROR (Status)) {
return Status;
}