Intel Extensible Firmware Interface - Manual (Page 255)

Protocols — EFI Driver Model
Version 1.10 12/01/02 9-13
Pseudo Code
Listed below are the algorithms for the Start() function for three different types of drivers.
How the Start() function of a driver is implemented can affect how the Supported()
function is implemented. All of the services in the EFI_DRIVER_BINDING_PROTOCOL need to
work together to make sure that all resources opened or allocated in Supported() and
Start() are released in Stop() .
The first algorithm is a simple device driver that does not create any additional handles. It only
attaches one or more protocols to an existing handle. The second is a simple bus driver that always
creates all of its child handles on the first call to
Start() . It does not attach any additional
protocols to the handle for the bus controller. The third is a more advanced bus driver that can
either create one child handles at a time on successive calls to
Start() , or it can create all of its
child handles or all of the remaining child handles in a single call to Start() . Once again, it does
not attach any additional protocols to the handle for the bus controller.
Device Driver:
1. Ignore the parameter RemainingDevicePath .
2. Open all required protocols with OpenProtocol() . A standard driver should use an
Attribute of EFI_OPEN_PROTOCOL_BY_DRIVER . If this driver needs exclusive access
to a protocol interface, and it requires any drivers that may be using the protocol interface to
disconnect, then the driver should use an
Attribute of
EFI_OPEN_PROTOCOL_BY_DRIVER | EFI_OPEN_PROTOCOL_EXCLUSIVE . It must
use the same Attribute value that was used in Supported() .
3. If any of the calls to OpenProtocol() in (2) returned an error, then close all of the protocols
opened in (2) with CloseProtocol() , and return the status code from the call to
OpenProtocol() that returned an error.
4. Initialize the device specified by ControllerHandle . If an error occurs, close all of the
protocols opened in (2) with CloseProtocol() , and return EFI_DEVICE_ERROR .
5. Allocate and initialize all of the data structures that this driver requires to manage the device
specified by ControllerHandle . This would include space for public protocols and space
for any additional private data structures that are related to ControllerHandle . If an error
occurs allocating the resources, then close all of the protocols opened in (2) with
CloseProtocol() , and return EFI_OUT_OF_RESOURCES .
6. Install all the new protocol interfaces onto ControllerHandle using
InstallMultipleProtocolInterfaces() . If an error occurs, close all of the
protocols opened in (1) with CloseProtocol() , and return the error from
InstallMultipleProtocolInterfaces () .
7. Return EFI_SUCCESS .