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Extensible Firmware Interface Specification
12-90 12/01/02 Version 1.10
Related Definitions
There are only two resource descriptor types from the ACPI Specification that may be used to
describe the current resources allocated to BAR of a PCI Controller. These are the QWORD
Address Space Descriptor (ACPI 2.0 Section 6.4.3.5.1), and the End Tag (ACPI 2.0
Section 6.4.2.8). The QWORD Address Space Descriptor can describe memory, I/O, and bus
number ranges for dynamic or fixed resources. The configuration of a BAR of a PCI Controller is
described with one or more QWORD Address Space Descriptors followed by an End Tag. Table
12-10 and Table 12-11 contain these two descriptor types. Please see the ACPI Specification for
details on the field values.
Table 12-10. ACPI 2.0 QWORD Address Space Descriptor
Byte
Offset
Byte
Length
Data
Description
0x00 0x01 0x8A QWORD Address Space Descriptor
0x01 0x02 0x2B Length of this descriptor in bytes not including the first two fields
0x03 0x01 Resource Type
0 – Memory Range
1 – I/O Range
2 – Bus Number Range
0x04 0x01 General Flags
0x05 0x01 Type Specific Flags
0x06 0x08 Address Space Granularity
0x0E 0x08 Address Range Minimum
0x16 0x08 Address Range Maximum
0x1E 0x08 Address Translation Offset
0x26 0x08 Address Length
Table 12-11. ACPI 2.0 End Tag
Byte
Offset
Byte
Length
Data
Description
0x00 0x01 0x79 End Tag
0x01 0x01 0x00 Checksum. If 0, then checksum is assumed to be valid.