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Version 1.10 12/01/02 C-5
C.4 Secondary Root PCI Bus with PCI to PCI Bridge
The secondary PCI host bridge materializes a second set of PCI buses into the system. The PCI
buses on the secondary PCI host bridge are totally independent of the PCI buses on the root PCI
host bridge. The only relationship between the two is they must be configured to not consume the
same resources. The primary PCI bus of the secondary PCI host bridge also contains a PCI to PCI
bridge. There is some arbitrary PCI device plugged in behind the PCI to PCI bridge in a PCI slot.
In ACPI this configuration is represented in the _SB, system bus tree, of the ACPI name space.
PCI1 is a child of _SB and it represents the secondary PCI host bridge. The PCI to PCI bridge and
the device plugged into the slot on its primary bus are not described in the ACPI name space.
These devices can be fully configured by following the applicable PCI specification.
The EFI Device Path for the secondary root PCI bridge with a PCI to PCI bridge is defined in
Table C-3. It would contain entries for the following things:
• Root PCI Bridge. ACPI Device Path _HID PNP0A03, _UID 1. ACPI name space \_SB\PCI1
• PCI to PCI Bridge. PCI Device Path with device and function of the PCI Bridge. ACPI name
space \_SB\PCI1, PCI to PCI bridges are defined by PCI specification and not ACPI.
• PCI Device. PCI Device Path with the device and function of the PCI device. ACPI name
space \_SB\PCI1, PCI devices are defined by PCI specification and not ACPI.
• End Device Path.
Table C-3. Secondary Root PCI Bus with PCI to PCI Bridge 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 0x0001 _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 0x00 PCI Function for PCI to PCI bridge
11 1 0x0c PCI Device for PCI to PCI bridge
12 1 0x01 Generic Device Path Header – Type Hardware Device Path
13 1 0x01 Sub type PCI Device Path
14 2 0x08 Length
16 1 0x00 PCI Function for PCI Device
17 1 0x00 PCI Device for PCI Device
18 1 0xFF Generic Device Path Header – Type End Device Path
19 1 0xFF Sub type – End Device Path
1A 2 0x04 Length