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