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Extensible Firmware Interface Specification
C-4 12/01/02 Version 1.10
In ACPI this configuration is represented in the _SB, system bus tree, of the ACPI name space.
PCI0 is a child of _SB and it represents the root PCI host bridge. The IDE controller appears to the
system to be a PCI device with some legacy properties, so it is represented as a child of PCI0 with
the name IDE0. PRIM is a child of IDE0 and it represents the primary ATA bus of the IDE
controller. MAST is a child of PRIM and it represents that this device is the ATA master device on
this primary ATA bus.
The EFI Device Path for the PCI IDE controller is defined in Table C-2. It would contain entries
for the following things:
• Root PCI Bridge. ACPI Device Path _HID PNP0A03, _UID 0. ACPI name space \_SB\PCI0
• PCI IDE controller. PCI Device Path with device and function of the IDE controller. ACPI
name space \_SB\PCI0\IDE0
• ATA Address. ATA Messaging Device Path for Primary bus and Master device. ACPI name
space \_SB\PCI0\IDE0\PRIM\MAST
• End Device Path
Table C-2. IDE Disk Device Path
Byte
Offset
Byte
Length
Data
Description
0 1 0x02 Generic Device Path Header – Type ACPI Device Path
1 1 0x01 Sub type – ACPI Device Path
2 2 0x0C Length
4 4 0x41D0,
0x0A03
_HID PNP0A03 – 0x41D0 represents a compressed string ‘PNP’ and is in
the low order bytes
8 4 0x0000 _UID
C 1 0x01 Generic Device Path Header – Type Hardware Device Path
D 1 0x01 Sub type PCI Device Path
E 2 0x06 Length
10 1 0x01 PCI Function
11 1 0x10 PCI Device
12 1 0x03 Generic Device Path Header – Messaging Device Path
13 1 0x01 Sub type – ATAPI Device Path
14 2 0x06 Length
16 1 0x00 Primary =0, Secondary = 1
17 1 0x00 Master = 0, Slave = 1
18 2 0x0000 LUN
1A 1 0xFF Generic Device Path Header – Type End Device Path
1B 1 0xFF Sub type – End Device Path
1C 2 0x04 Length