UEFI Device Paths

• There are six major types of Device Path nodes according to the Intel Specification version 1.10, dated December 1, 2002:
  1. Hardware Device Path. This Device Path defines how a device is attached to the resource domain of a system, where resource domain is simply the shared memory, memory mapped I/O, and I/O space of the system.
  2. ACPI Device Path. This Device Path is used to describe devices whose enumeration is not described in an industry-standard fashion. These devices must be described using ACPI AML in the ACPI name space; this Device Path is a linkage to the ACPI name space.
  3. Messaging Device Path. This Device Path is used to describe the connection of devices outside the resource domain of the system. This Device Path can describe physical messaging information (e.g., a SCSI ID) or abstract information (e.g., networking protocol IP addresses).
  4. Media Device Path. This Device Path is used to describe the portion of a medium that is being abstracted by a boot service. For example, a Media Device Path could define which partition on a hard drive was being used.
  5. BIOS Boot Specification Device Path. This Device Path is used to point to boot legacy operating systems; it is based on the BIOS Boot Specification Version 1.01. Refer to the References appendix for details on obtaining this specification.
  6. End of Hardware Device Path. Depending on the Sub-Type, this Device Path node is used to indicate the end of the Device Path instance or Device Path structure.
• These paths are detailed in the programming libraries for the EBC and vital for the booting process.