Intel Extensible Firmware Interface - Manual (Page 250)

Extensible Firmware Interface Specification
9-8 12/01/02 Version 1.10
Bus Driver that creates all of its child handles on the first call to Start():
1. Check the contents of the first Device Path Node of RemainingDevicePath to make sure
it is a legal Device Path Node for this bus driver’s children. If it is not, then return
EFI_UNSUPPORTED .
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 .
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. Use the protocol instances opened in (2) to test to see if this driver supports the controller.
Sometimes, just the presence of the protocols is enough of a test. Other times, the services of
the protocols opened in (2) are used to further check the identity of the controller. If any of
these tests fails, then close all the protocols opened in (2) with
CloseProtocol() and
return EFI_UNSUPPORTED .
5. Close all protocols opened in (2) with CloseProtocol() .
6. Return EFI_SUCCESS .
Bus Driver that is able to create all or one of its child handles on each call to Start():
1. Check the contents of the first Device Path Node of RemainingDevicePath to make sure
it is a legal Device Path Node for this bus driver’s children. If it is not, then return
EFI_UNSUPPORTED .
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 .
3. If any of the calls to OpenProtocol() in (2) failed with an error other than
EFI_ALREADY_STARTED , then close all of the protocols opened in (2) that did not return
EFI_ALREADY_STARTED with CloseProtocol() , and return the status code from the
OpenProtocol() call that returned an error.
4. Use the protocol instances opened in (2) to test to see if this driver supports the controller.
Sometimes, just the presence of the protocols is enough of a test. Other times, the services of
the protocols opened in (2) are used to further check the identity of the controller. If any of
these tests fails, then close all the protocols opened in (2) that did not return
EFI_ALREADY_STARTED with CloseProtocol() and return EFI_UNSUPPORTED .
5. Close all protocols opened in (2) that did not return EFI_ALREADY_STARTED with
CloseProtocol() .
6. Return EFI_SUCCESS .