What is acpi in linux

ACPI

ACPI (Advanced Configuration and Power Management Interface) is a power management system that is part of the BIOS.

Installation

Kernel

The following kernel options need to be activated for ACPI:

Power management and ACPI options ---> [*] Power Management support [*] ACPI (Advanced Configuration and Power Interface) Support --->

Optional drivers

Option	Module	Recommend	Description
Deprecated /proc/acpi files	—	No	Creates deprecated files in the procfs filesystem, which are now replaced by files in the sysfs filesystem.
Deprecated power /proc/acpi directories	—	No	Creates deprecated files in the procfs filesystem, which are now replaced by files in the sysfs filesystem.
EC read/write access through /sys/kernel/debug/ec	ec-debugfs	No	Debug interface to the Embedded Controller.
Deprecated /proc/acpi/event support	—	No	Creates deprecated files in the procfs filesystem, which are now replaced by the input layer or netlink events.
AC Adapter	ac	Laptops	Creates files to tell if your system is connected to AC.
Battery	battery	Laptops	Creates files to tell if your system is powered by a battery.
Button	button	—	Handles events on the power, sleep, and lid buttons.
Video	video	—	Supports basic operations for Video cards.
Fan	fan	—	Supports ACPI fan devices, allowing user-mode applications to perform basic fan control (on, off, status).
Dock	dock	—	Supports ACPI-controlled docking stations and removable drive bays, see the acpi dock article.
Processor	processor	—	Installs ACPI as the idle handler for Linux and uses ACPI C2 and C3 processor states to save power.
Processor Aggregator	processor-aggregator	—	ACPI 4.0 function to perform specific processor configuration and control.
Thermal Zone	thermal	Yes	Supports ACPI thermal zones to protect your processor against overheating.
NUMA support	—	—
Debug Statements	—	No
PCI slot detection driver	pci-slot	No	Helps to correlate PCI bus addresses with physical slots
Container and Module Devices	container	—	Supports ACPI Container and Module devices to hotplug nodes, CPUs, and memory.
Smart Battery System	sbs, sbshc	—	Supports another type of access to battery information, found on some laptops.
Hardware Error Device	hed	—	Supports the Hardware Error Device, which is used to report some hardware errors.
Allow ACPI methods to be inserted/replaced at run time	custom-method	No
ACPI Platform Error Interface (APEI)	—	—	APEI allows to report errors (for example from the chipset) to the operating system.

Emerge

Desktop environments react on the common events generated by ACPI. If a desktop environment is not installed or to have the system react on special events the ACPI package can be installed. Install the sys-power/acpid package:

USE flags

Several packages know about the global acpi USE flag. There are no use flags available for sys-power/acpid at this time.

SELinux

For acpid to be able to shutdown a SELinux system, make sure the sec-policy/selinux-shutdown package is installed and the /sbin/shutdown executable is re-labelled:

Configuration

The scripts found in /etc/acpi define how the system reacts on ACPI events. They can be edited as necessary to meet the user’s needs.

Services

OpenRC

The acpid service can now be started. While using OpenRC run:

To have the acpid service start at boot time add it to the default runlevel:

systemd

If systemd is being used as the init system, enable the acpid service on system boot by issuing:

Advanced examples

The default ACPI setup may be satisfactory for some users, however a little extra configuration may be required to get the acpid daemon to treat some basic ACPI events properly (AC power plug in/out, multimedia keys, etc.).

Modifications can be make to /etc/acpi/default.sh along with /etc/acpi/events/default if necessary. Why not create a complicated setup that makes use of the /etc/acpi/actions and /etc/acpi/events capabilities? Simply put scripts and event files in those locations for advanced usage.

A basic default.sh file will probably be enough for most users, however the following is an example of what could be done using default.sh :

 
#!/bin/sh # # $Header: /etc/acpi/default.sh Exp $ # $Author: (c) 2012-2014 -tclover Exp $ # $License: MIT (or 2-clause/new/simplified BSD) Exp $ # $Version: 2014/12/24 21:09:26 Exp $ # log()  logger -p daemon "ACPI: $*"; > uhd()  log "event unhandled: $*"; > set $* group=$1%/*> action=$1#*/> device=$2 id=$3 value=$4 [ -d /dev/snd ] && alsa=true || alsa=false [ -d /dev/oss ] && oss=true || oss=false amixer="amixer -q set Master" ossmix="ossmix -- vmix0-outvol" case $group in ac_adapter) case $value in *0) log "switching to power.bat power profile" hprofile power.bat;; *1) log "switching to power.adp power profile" hprofile power.adp;; *) uhd $*;; esac ;; battery) case $value in *0) log "switching to power.adp power profile" hprofile power.adp;; *1) log "switching to power.adp power profile" hprofile power.adp;; *) uhd $*;; esac ;; button) case $action in lid) case "$id" in close) hibernate-ram;; open) :;; *) uhd $*;; esac ;; power) shutdown -H now;; sleep) hibernate-ram;; mute) $alsa && $amixer toggle;; volumeup) $alsa && $amixer 3dB+ $oss && $ossmix +3;; volumedown) $alsa && $amixer 3dB- $oss && $ossmix -3;; *) uhd $*;; esac ;; cd) case $action in play) :;; stop) :;; prev) :;; next) :;; *) uhd $*;; esac ;; jack) case $id in *plug) :;; *) uhd $*;; esac ;; video) case $action in displayoff) :;; *) uhd $*;; esac ;; *) uhd $*;; esac unset alsa oss amixer ossmix group action device id # vim:fenc=utf-8:ft=sh:ci:pi:sts=4:sw=4:ts=4: 
 
Note
Notice that the above script is compatible with ALSA and OSS, so no extra actions are needed when switching OSS from ALSA or the opposite. Do not hesitate to edit the script!
 
Note
The above script also makes use of a power management profile using hprofile. Refer to the hprofile article for more information.
 
Userspace utilities
 
Many packages use ACPI functions. A few are listed here:
 
 
sys-power/acpi: to show information from the /proc filesystem, such as battery status or thermal information
 
sys-power/acpitool: a small command line application, intended to be a replacement for the apm tool
 
sys-power/acpilight: replacement for xbacklight that uses the ACPI interface to set brightness
 
app-laptop/laptop-mode-tools: linux kernel laptop_mode user-space utilities
 
x11-misc/cbatticon: a lightweight and fast battery icon that sits in your system tray
 
app-admin/conky: an advanced, highly configurable system monitor for X
 
 
See also
 
 
ACPI/ThinkPad-special-buttons — describes how to configure ACPI events and actions for the Lenovo ThinkPad T410 laptop.
 
Suspend and hibernate — describes how to suspend or hibernate a Gentoo system.
 
Knowledge Base:Disabling ACPI support at boot time
 
 
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