Documentation/firmware-guide/acpi/debug.rst

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====================
ACPI CA Debug Output
====================

The ACPI CA can generate debug output.  This document describes how to use this
facility.

Compile-time configuration
==========================

The ACPI CA debug output is globally enabled by CONFIG_ACPI_DEBUG.  If this
config option is not set, the debug messages are not even built into the kernel.

Boot- and run-time configuration
================================

When CONFIG_ACPI_DEBUG=y, you can select the component and level of messages
you're interested in.  At boot-time, use the acpi.debug_layer and
acpi.debug_level kernel command line options.  After boot, you can use the
debug_layer and debug_level files in /sys/module/acpi/parameters/ to control
the debug messages.

debug_layer (component)
=======================

The "debug_layer" is a mask that selects components of interest, e.g., a
specific part of the ACPI interpreter.  To build the debug_layer bitmask, look
for the "#define _COMPONENT" in an ACPI source file.

You can set the debug_layer mask at boot-time using the acpi.debug_layer
command line argument, and you can change it after boot by writing values
to /sys/module/acpi/parameters/debug_layer.

The possible components are defined in include/acpi/acoutput.h.

Reading /sys/module/acpi/parameters/debug_layer shows the supported mask values::

    ACPI_UTILITIES                  0x00000001
    ACPI_HARDWARE                   0x00000002
    ACPI_EVENTS                     0x00000004
    ACPI_TABLES                     0x00000008
    ACPI_NAMESPACE                  0x00000010
    ACPI_PARSER                     0x00000020
    ACPI_DISPATCHER                 0x00000040
    ACPI_EXECUTER                   0x00000080
    ACPI_RESOURCES                  0x00000100
    ACPI_CA_DEBUGGER                0x00000200
    ACPI_OS_SERVICES                0x00000400
    ACPI_CA_DISASSEMBLER            0x00000800
    ACPI_COMPILER                   0x00001000
    ACPI_TOOLS                      0x00002000

debug_level
===========

The "debug_level" is a mask that selects different types of messages, e.g.,
those related to initialization, method execution, informational messages, etc.
To build debug_level, look at the level specified in an ACPI_DEBUG_PRINT()
statement.

The ACPI interpreter uses several different levels, but the Linux
ACPI core and ACPI drivers generally only use ACPI_LV_INFO.

You can set the debug_level mask at boot-time using the acpi.debug_level
command line argument, and you can change it after boot by writing values
to /sys/module/acpi/parameters/debug_level.

The possible levels are defined in include/acpi/acoutput.h.  Reading

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