Device Path Protocol
Version 1.02 12/12/00 131
5.3.5.2 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 5-23. 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.
5.3.5.3 Vendor-Defined Media Device Path
Table 5-24. Vendor-Defined Media Device Path
Mnemonic
Byte
Offset
Byte
Length Description
Type 0 1 Type 4 – Media Device Path.
Sub-Type 1 1 Sub-Type 3 – Vendor.
Length 2 2 Length of this structure in bytes. Length is 20 + n bytes.
Vendor_GUID 4 16 Vendor-assigned GUID that defines the data that follows.
Vendor Defined Data 20 n Vendor-defined variable size data.
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