Intel Extensible Firmware Interface - Manual (Page 398)

Extensible Firmware Interface Specification
11-38 12/01/02 Version 1.10
Description
The EFI_DISK_IO protocol is used to control block I/O interfaces.
The disk I/O functions allow I/O operations that need not be on the underlying device’s block
boundaries or alignment requirements. This is done by copying the data to/from internal buffers as
needed to provide the proper requests to the block I/O device. Outstanding write buffer data is
flushed by using the
Flush() function of the EFI_BLOCK_IO protocol on the device handle.
The firmware automatically adds an EFI_DISK_IO interface to any EFI_BLOCK_IO interface
that is produced. It also adds file system, or logical block I/O, interfaces to any EFI_DISK_IO
interface that contains any recognized file system or logical block I/O devices. The firmware must
automatically support the following required formats:
• The EFI FAT12, FAT16, and FAT32 file system type.
• The legacy master boot record partition block. (The presence of this on any block I/O device
is optional, but if it is present the firmware is responsible for allocating a logical device for
each partition).
• The extended partition record partition block.
• The El Torito logical block devices.