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.. SPDX-License-Identifier: GPL-2.0
=================
ACPI Debug Output
=================
The ACPI CA, the Linux ACPI core, and some ACPI drivers can generate debug
output. This document describes how to use this facility.
Compile-time configuration
==========================
ACPI debug output is globally enabled by CONFIG_ACPI_DEBUG. If this config
option is turned off, 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 driver or 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 and
include/acpi/acpi_drivers.h. Reading /sys/module/acpi/parameters/debug_layer
shows the supported mask values, currently these::
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
ACPI_BUS_COMPONENT 0x00010000
ACPI_AC_COMPONENT 0x00020000
ACPI_BATTERY_COMPONENT 0x00040000
ACPI_BUTTON_COMPONENT 0x00080000
ACPI_SBS_COMPONENT 0x00100000
ACPI_FAN_COMPONENT 0x00200000
ACPI_PCI_COMPONENT 0x00400000
ACPI_CONTAINER_COMPONENT 0x01000000
ACPI_SYSTEM_COMPONENT 0x02000000
ACPI_THERMAL_COMPONENT 0x04000000
ACPI_MEMORY_DEVICE_COMPONENT 0x08000000
ACPI_VIDEO_COMPONENT 0x10000000
ACPI_PROCESSOR_COMPONENT 0x20000000
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
/sys/module/acpi/parameters/debug_level shows the supported mask values,
currently these::
ACPI_LV_INIT 0x00000001
ACPI_LV_DEBUG_OBJECT 0x00000002
ACPI_LV_INFO 0x00000004
ACPI_LV_INIT_NAMES 0x00000020
ACPI_LV_PARSE 0x00000040
ACPI_LV_LOAD 0x00000080
ACPI_LV_DISPATCH 0x00000100
ACPI_LV_EXEC 0x00000200
ACPI_LV_NAMES 0x00000400
ACPI_LV_OPREGION 0x00000800
ACPI_LV_BFIELD 0x00001000
ACPI_LV_TABLES 0x00002000
ACPI_LV_VALUES 0x00004000
ACPI_LV_OBJECTS 0x00008000
ACPI_LV_RESOURCES 0x00010000
ACPI_LV_USER_REQUESTS 0x00020000
ACPI_LV_PACKAGE 0x00040000
ACPI_LV_ALLOCATIONS 0x00100000
ACPI_LV_FUNCTIONS 0x00200000
ACPI_LV_OPTIMIZATIONS 0x00400000
ACPI_LV_MUTEX 0x01000000
ACPI_LV_THREADS 0x02000000
ACPI_LV_IO 0x04000000
ACPI_LV_INTERRUPTS 0x08000000
ACPI_LV_AML_DISASSEMBLE 0x10000000
ACPI_LV_VERBOSE_INFO 0x20000000
ACPI_LV_FULL_TABLES 0x40000000
ACPI_LV_EVENTS 0x80000000
Examples
========
For example, drivers/acpi/bus.c contains this::
#define _COMPONENT ACPI_BUS_COMPONENT
...
ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Device insertion detected\n"));
To turn on this message, set the ACPI_BUS_COMPONENT bit in acpi.debug_layer
and the ACPI_LV_INFO bit in acpi.debug_level. (The ACPI_DEBUG_PRINT
statement uses ACPI_DB_INFO, which is macro based on the ACPI_LV_INFO
definition.)
Enable all AML "Debug" output (stores to the Debug object while interpreting
AML) during boot::
acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Enable PCI and PCI interrupt routing debug messages::
acpi.debug_layer=0x400000 acpi.debug_level=0x4
Enable all ACPI hardware-related messages::
acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Enable all ACPI_DB_INFO messages after boot::
# echo 0x4 > /sys/module/acpi/parameters/debug_level
Show all valid component values::
# cat /sys/module/acpi/parameters/debug_layer
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