Extensible Firmware Interface Specification
22 12/12/00 Version 1.02

Table 2-5. Required EFI Implementation Elements (continued)

Element Description
SIMPLE_INPUT protocol Protocol interfaces for devices that support simple console style text
input.
SIMPLE_TEXT_OUTPUT protocol Protocol interfaces for devices that support console style text
displaying.
UNICODE_COLLATION protocol1Protocol interfaces for Unicode string comparison operations.
1 These protocols are not required if the implementation can operate using on the LOAD_FILE protocol.
2.5.2 Optional Elements

Table 2-6 lists the optional elements. Any system that is designed to conform to the EFI

specification may choose whether or not to provide a complete implementation of all these

elements. However, any system choosing to provide an implementation of one of these optional

elements must do so to the same extent as for required elements. In other words, an

implementation of any single optional element of this specification must include all the functions

defined as part of the option and must deliver the full semantics defined for the services for all

combinations of calls and parameters.

Table 2-6. Optional EFI Implementation Elements

Element Description
SERIAL_IO protocol Protocol interfaces for byte stream devices.
SIMPLE_NETWORK protocol Protocol interfaces for devices that support packet based transfers.
PXE_BC protocol Protocol interfaces for devices that support PXE I/O network access.
Partitioning1Functionality to provide BLOCK_IO interfaces for logical block
devices as defined by partition table, or El Torito “no emulation”
device.
BLOCK_IO protocol1Protocol interfaces for devices that support block I/O style accesses.
DISK_IO protocol1Protocol interfaces for providing disk IO from a BLOCK_IO interface.
SIMPLE_FILE_SYSTEM protocol1Protocol interfaces for opening disk volumes through a DISK_IO
interface.
EFI_FILE_HANDLE protocol1Protocol interfaces for accessing the device with file I/O style
accesses through a DISK_IO interface.
UNICODE_COLLATION protocol1Protocol interfaces for Unicode string comparison operations.
1These protocols are not optional if the implementation requires them to support SIMPLE_FILE_SYSTEM
protocol.