Advanced Configuration and Power Interface Specification

Device Configuration
Section 8.4.4.3, RDI in Section 8.5, and passive power resources in Section 7.2.5), and supports
processor containers (see Section 8.4.3.1).
Return Value Information
Capabilities Buffer (Buffer) – The platform acknowledges the Capabilities Buffer by returning a
buffer of DWORDs of the same length. Set bits indicate acknowledgment and cleared bits indicate
that the platform does not support the capability.
6.2.11.3 OSC Implementation Example for PCI Host Bridge Devices
The following section is an excerpt from the PCI Firmware Specification Revision 3.0 and is
reproduced with the permission of the PCI SIG.
Note: The PCI SIG owns the definition of _OSC behavior and parameter bit definitions for PCI devices.
In the event of a discrepancy between the following example and the PCI Firmware Specification,
the latter has precedence.
The _OSC interface defined in this section applies only to “Host Bridge” ACPI devices that
originate PCI, PCI-X or PCI Express hierarchies. These ACPI devices must have a _HID of (or
_CID including) either EISAID(“PNP0A03”) or EISAID(“PNP0A08”). For a host bridge device that
originates a PCI Express hierarchy, the _OSC interface defined in this section is required. For a host
bridge device that originates a PCI/PCI-X bus hierarchy, inclusion of an _OSC object is optional.
• The _OSC interface for a PCI/PCI-X/PCI Express hierarchy is identified by the following
Universal Uniform Identifier (UUID):
33DB4D5B-1FF7-401C-9657-7441C03DD766
A revision ID of 1 encompasses fields defined in this section of this revision of this specification,
comprised of 3 DWORDs, including the first DWORD described by the generic ACPI definition of
_OSC.
The first DWORD in the _OSC Capabilities Buffer contain bits are generic to _OSC and include
status and error information.
The second DWORD in the _OSC capabilities buffer is the Support Field. Bits defined in the
Support Field provide information regarding OS supported features. Contents in the Support Field
are passed one-way; the OS will disregard any changes to this field when returned. See Table 6-174
for descriptions of capabilities bits in this field passed as a parameter into the _OSC control method.
The third DWORD in the _OSC Capabilities Buffer is the Control Field. Bits defined in the Control
Field are used to submit request by the OS for control/handling of the associated feature, typically
(but not excluded to) those features that utilize native interrupts or events handled by an OS-level
driver. See Table 6-176 for descriptions of capabilities bits in this field passed as a parameter into
the _OSC control method. If any bits in the Control Field are returned cleared (masked to zero) by
the _OSC control method, the respective feature is designated unsupported by the platform and must
not be enabled by the OS. Some of these features may be controlled by platform firmware prior to
OS boot or during runtime for a legacy OS, while others may be disabled/inoperative until native OS
support is available. See Table 6-177 for descriptions of capabilities bits in this returned field.
If the _OSC control method is absent from the scope of a host bridge device, then the OS must not
enable or attempt to use any features defined in this section for the hierarchy originated by the host
bridge. Doing so could contend with platform firmware operations, or produce undesired results. It
is recommended that a machine with multiple host bridge devices should report the same capabilities
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