--- /dev/null
+ 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_POWER_COMPONENT 0x00800000
+ 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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