1.. SPDX-License-Identifier: GPL-2.0
2
3=================
4ACPI Debug Output
5=================
6
7The ACPI CA, the Linux ACPI core, and some ACPI drivers can generate debug
8output.  This document describes how to use this facility.
9
10Compile-time configuration
11==========================
12
13ACPI debug output is globally enabled by CONFIG_ACPI_DEBUG.  If this config
14option is turned off, the debug messages are not even built into the
15kernel.
16
17Boot- and run-time configuration
18================================
19
20When CONFIG_ACPI_DEBUG=y, you can select the component and level of messages
21you're interested in.  At boot-time, use the acpi.debug_layer and
22acpi.debug_level kernel command line options.  After boot, you can use the
23debug_layer and debug_level files in /sys/module/acpi/parameters/ to control
24the debug messages.
25
26debug_layer (component)
27=======================
28
29The "debug_layer" is a mask that selects components of interest, e.g., a
30specific driver or part of the ACPI interpreter.  To build the debug_layer
31bitmask, look for the "#define _COMPONENT" in an ACPI source file.
32
33You can set the debug_layer mask at boot-time using the acpi.debug_layer
34command line argument, and you can change it after boot by writing values
35to /sys/module/acpi/parameters/debug_layer.
36
37The possible components are defined in include/acpi/acoutput.h and
38include/acpi/acpi_drivers.h.  Reading /sys/module/acpi/parameters/debug_layer
39shows the supported mask values, currently these::
40
41    ACPI_UTILITIES                  0x00000001
42    ACPI_HARDWARE                   0x00000002
43    ACPI_EVENTS                     0x00000004
44    ACPI_TABLES                     0x00000008
45    ACPI_NAMESPACE                  0x00000010
46    ACPI_PARSER                     0x00000020
47    ACPI_DISPATCHER                 0x00000040
48    ACPI_EXECUTER                   0x00000080
49    ACPI_RESOURCES                  0x00000100
50    ACPI_CA_DEBUGGER                0x00000200
51    ACPI_OS_SERVICES                0x00000400
52    ACPI_CA_DISASSEMBLER            0x00000800
53    ACPI_COMPILER                   0x00001000
54    ACPI_TOOLS                      0x00002000
55    ACPI_BUS_COMPONENT              0x00010000
56    ACPI_AC_COMPONENT               0x00020000
57    ACPI_BATTERY_COMPONENT          0x00040000
58    ACPI_BUTTON_COMPONENT           0x00080000
59    ACPI_SBS_COMPONENT              0x00100000
60    ACPI_FAN_COMPONENT              0x00200000
61    ACPI_PCI_COMPONENT              0x00400000
62    ACPI_POWER_COMPONENT            0x00800000
63    ACPI_CONTAINER_COMPONENT        0x01000000
64    ACPI_SYSTEM_COMPONENT           0x02000000
65    ACPI_THERMAL_COMPONENT          0x04000000
66    ACPI_MEMORY_DEVICE_COMPONENT    0x08000000
67    ACPI_VIDEO_COMPONENT            0x10000000
68    ACPI_PROCESSOR_COMPONENT        0x20000000
69
70debug_level
71===========
72
73The "debug_level" is a mask that selects different types of messages, e.g.,
74those related to initialization, method execution, informational messages, etc.
75To build debug_level, look at the level specified in an ACPI_DEBUG_PRINT()
76statement.
77
78The ACPI interpreter uses several different levels, but the Linux
79ACPI core and ACPI drivers generally only use ACPI_LV_INFO.
80
81You can set the debug_level mask at boot-time using the acpi.debug_level
82command line argument, and you can change it after boot by writing values
83to /sys/module/acpi/parameters/debug_level.
84
85The possible levels are defined in include/acpi/acoutput.h.  Reading
86/sys/module/acpi/parameters/debug_level shows the supported mask values,
87currently these::
88
89    ACPI_LV_INIT                    0x00000001
90    ACPI_LV_DEBUG_OBJECT            0x00000002
91    ACPI_LV_INFO                    0x00000004
92    ACPI_LV_INIT_NAMES              0x00000020
93    ACPI_LV_PARSE                   0x00000040
94    ACPI_LV_LOAD                    0x00000080
95    ACPI_LV_DISPATCH                0x00000100
96    ACPI_LV_EXEC                    0x00000200
97    ACPI_LV_NAMES                   0x00000400
98    ACPI_LV_OPREGION                0x00000800
99    ACPI_LV_BFIELD                  0x00001000
100    ACPI_LV_TABLES                  0x00002000
101    ACPI_LV_VALUES                  0x00004000
102    ACPI_LV_OBJECTS                 0x00008000
103    ACPI_LV_RESOURCES               0x00010000
104    ACPI_LV_USER_REQUESTS           0x00020000
105    ACPI_LV_PACKAGE                 0x00040000
106    ACPI_LV_ALLOCATIONS             0x00100000
107    ACPI_LV_FUNCTIONS               0x00200000
108    ACPI_LV_OPTIMIZATIONS           0x00400000
109    ACPI_LV_MUTEX                   0x01000000
110    ACPI_LV_THREADS                 0x02000000
111    ACPI_LV_IO                      0x04000000
112    ACPI_LV_INTERRUPTS              0x08000000
113    ACPI_LV_AML_DISASSEMBLE         0x10000000
114    ACPI_LV_VERBOSE_INFO            0x20000000
115    ACPI_LV_FULL_TABLES             0x40000000
116    ACPI_LV_EVENTS                  0x80000000
117
118Examples
119========
120
121For example, drivers/acpi/bus.c contains this::
122
123    #define _COMPONENT              ACPI_BUS_COMPONENT
124    ...
125    ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Device insertion detected\n"));
126
127To turn on this message, set the ACPI_BUS_COMPONENT bit in acpi.debug_layer
128and the ACPI_LV_INFO bit in acpi.debug_level.  (The ACPI_DEBUG_PRINT
129statement uses ACPI_DB_INFO, which is macro based on the ACPI_LV_INFO
130definition.)
131
132Enable all AML "Debug" output (stores to the Debug object while interpreting
133AML) during boot::
134
135    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
136
137Enable PCI and PCI interrupt routing debug messages::
138
139    acpi.debug_layer=0x400000 acpi.debug_level=0x4
140
141Enable all ACPI hardware-related messages::
142
143    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
144
145Enable all ACPI_DB_INFO messages after boot::
146
147    # echo 0x4 > /sys/module/acpi/parameters/debug_level
148
149Show all valid component values::
150
151    # cat /sys/module/acpi/parameters/debug_layer
152