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