Documentation/firmware-guide/acpi/namespace.rst

Source file repositories/reference/linux-study-clean/Documentation/firmware-guide/acpi/namespace.rst

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Corpus path: Documentation/firmware-guide/acpi/namespace.rst
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Domain: Support Tooling And Documentation
Bucket: Documentation
Inferred role: Support Tooling And Documentation: documentation
Status: atlas-only

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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.
Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

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Annotated Snippet

.. SPDX-License-Identifier: GPL-2.0
.. include:: <isonum.txt>

===================================================
ACPI Device Tree - Representation of ACPI Namespace
===================================================

:Copyright: |copy| 2013, Intel Corporation

:Author: Lv Zheng <lv.zheng@intel.com>

:Credit:   Thanks for the help from Zhang Rui <rui.zhang@intel.com> and
           Rafael J.Wysocki <rafael.j.wysocki@intel.com>.

Abstract
========
The Linux ACPI subsystem converts ACPI namespace objects into a Linux
device tree under the /sys/devices/LNXSYSTM:00 and updates it upon
receiving ACPI hotplug notification events.  For each device object
in this hierarchy there is a corresponding symbolic link in the
/sys/bus/acpi/devices.

This document illustrates the structure of the ACPI device tree.

ACPI Definition Blocks
======================

The ACPI firmware sets up RSDP (Root System Description Pointer) in the
system memory address space pointing to the XSDT (Extended System
Description Table).  The XSDT always points to the FADT (Fixed ACPI
Description Table) using its first entry, the data within the FADT
includes various fixed-length entries that describe fixed ACPI features
of the hardware.  The FADT contains a pointer to the DSDT
(Differentiated System Description Table).  The XSDT also contains
entries pointing to possibly multiple SSDTs (Secondary System
Description Table).

The DSDT and SSDT data is organized in data structures called definition
blocks that contain definitions of various objects, including ACPI
control methods, encoded in AML (ACPI Machine Language).  The data block
of the DSDT along with the contents of SSDTs represents a hierarchical
data structure called the ACPI namespace whose topology reflects the
structure of the underlying hardware platform.

The relationships between ACPI System Definition Tables described above
are illustrated in the following diagram::

   +---------+    +-------+    +--------+    +------------------------+
   |  RSDP   | +->| XSDT  | +->|  FADT  |    |  +-------------------+ |
   +---------+ |  +-------+ |  +--------+  +-|->|       DSDT        | |
   | Pointer | |  | Entry |-+  | ...... |  | |  +-------------------+ |
   +---------+ |  +-------+    | X_DSDT |--+ |  | Definition Blocks | |
   | Pointer |-+  | ..... |    | ...... |    |  +-------------------+ |
   +---------+    +-------+    +--------+    |  +-------------------+ |
                  | Entry |------------------|->|       SSDT        | |
                  +- - - -+                  |  +-------------------| |
                  | Entry | - - - - - - - -+ |  | Definition Blocks | |
                  +- - - -+                | |  +-------------------+ |
                                           | |  +- - - - - - - - - -+ |
                                           +-|->|       SSDT        | |
                                             |  +-------------------+ |
                                             |  | Definition Blocks | |
                                             |  +- - - - - - - - - -+ |
                                             +------------------------+
                                                          |
                                             OSPM Loading |
                                                         \|/
                                                   +----------------+
                                                   | ACPI Namespace |
                                                   +----------------+

Annotation

Atlas domain: Support Tooling And Documentation / Documentation.
Implementation status: atlas-only.

Implementation Notes

This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.