Intel Extensible Firmware Interface - Manual (Page 237)

Protocols — Device Path Protocol
Version 1.10 12/01/02 8-17
The following structure defines a MBR for EFI:
typedef struct _MBR_PARTITION {
UINT8 BootIndicator; // 0x80 for active partition
UINT8 PartitionStartCHS[3];
UINT8 OS_Indicator;
UINT8 PartitionEndCHS[3];
UINT32 PartitionStartingLBA;
UINT32 PartitionSizeInLBA;
} MBR_PARTITION;
typedef struct _PC_MBR {
UINT8
MBRCode[0x1BE];
MBR_PARTITION PartitionEntry[4];
UINT16 Signature; // Must be 0xaa55
} PC_MBR;
8.3.5.2 CD-ROM Media Device Path
The CD-ROM Media Device Path is used to define a system partition that exists on a CD-ROM.
The CD-ROM is assumed to contain an ISO-9660 file system and follow the CD-ROM “El Torito”
format. The Boot Entry number from the Boot Catalog is how the “El Torito” specification defines
the existence of bootable entities on a CD-ROM. In EFI the bootable entity is an EFI System
Partition that is pointed to by the Boot Entry.
Table 8-25. CD-ROM Media Device Path
Mnemonic Byte
Offset Byte
Length
Description
Type 0 1 Type 4 – Media Device Path.
Sub-Type 1 1 Sub-Type 2 – CD-ROM “El Torito” Format.
Length 2 2 Length of this structure in bytes. Length is 24 bytes.
Boot Entry 4 4 Boot Entry number from the Boot Catalog. The
Initial/Default entry is defined as zero.
Partition Start 8 8 Starting RBA of the partition on the medium. CD-ROMs use
Relative logical Block Addressing.
Partition Size 16 8 Size of the partition in units of Blocks, also called Sectors.