Advanced Configuration and Power Interface Specification

ACPI Software Programming Model
Name
\_PR
\_SB
\_SI
\_TZ
Description
ACPI 1.0 Processor Namespace. ACPI 1.0 requires all Processor objects to be defined under
this namespace. ACPI 2.0 and later allow Processor object definitions under the \_SB
namespace. Platforms may maintain the \_PR namespace for compatibility with ACPI 1.0
operating systems, but it is otherwise deprecated. see the compatibility note in
Section 5.2.12.12. An ACPI-compatible namespace may define Processor objects in either the
\_SB or \_PR scope but not both.
For more information about defining Processor objects, see Section 8, “Processor
Configuration and Control.”
All Device/Bus Objects are defined under this namespace.
System indicator objects are defined under this namespace. For more information about
defining system indicators, see Section 9.1, \_SI System Indicators.”
ACPI 1.0 Thermal Zone namespace. ACPI 1.0 requires all Thermal Zone objects to be defined
under this namespace. Thermal Zone object definitions may now be defined under the \_SB
namespace. ACPI-compatible systems may maintain the \_TZ namespace for compatibility
with ACPI 1.0 operating systems. An ACPI-compatible namespace may define Thermal Zone
objects in either the \_SB or \_TZ scope but not both.
For more information about defining Thermal Zone objects, see Section 11, “Thermal
Management.”
5.3.2 Objects
All objects, except locals, have a global scope. Local data objects have a per-invocation scope and
lifetime and are used to process the current invocation from beginning to end.
The contents of objects vary greatly. Nevertheless, most objects refer to data variables of any
supported data type, a control method, or system software-provided functions.
Objects may contain a revision field. Successive ACPI specifications define object revisions so that
they are backwards compatible with OSPM implementations that support previous specifications /
object revisions. New object fields are added at the end of previous object definitions. OSPM
interprets objects according to the revision number it supports including all earlier revisions. As
such, OSPM expects that an object’s length can be greater than or equal to the length of the known
object revision. When evaluating objects with revision numbers greater than that known by OSPM,
OSPM ignores internal object fields values that are beyond the defined object field range for the
known revision.
5.4 Definition Block Encoding
This section specifies the encoding used in a Definition Block to define names (load time only),
objects, and packages. The Definition Block is encoded as a stream from beginning to end. The lead
byte in the stream comes from the AML encoding tables shown in Section 19, “ACPI Source
Language (ASL) Reference,” and signifies how to interpret some number of following bytes, where
each following byte can in turn signify how to interpret some number of following bytes. For a full
specification of the AML encoding, see Section 19, “ACPI Source Language (ASL) Reference.”
Within the stream there are two levels of data being defined. One is the packaging and object
declarations (load time), and the other is an object reference (package contents/run-time).
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