ACPI modules

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From ACPI site:

ACPI (Advanced Configuration and Power Interface) is an open industry specification co-developed by Hewlett-Packard, Intel, Microsoft, Phoenix, and Toshiba.

ACPI modules are kernel modules for different ACPI parts. They enable special ACPI functions or add information to /proc or /sys. These information can be parsed by acpid for events or other monitoring applications.

Which modules are available?

This is a small list and summary of ACPI kernel modules:

  • ac (power connector status)
  • asus-laptop (useful on ASUS/medion laptops)
  • battery (battery status)
  • bay (bay status)
  • button (catch button events, like LID or POWER BUTTON)
  • container (container status)
  • dock (docking station status)
  • fan (fan status)
  • i2c_ec (EC SMBUs driver)
  • thinkpad_acpi (useful on Lenovo Thinkpad laptops)
  • processor (processor status)
  • sbs (smart battery status)
  • thermal (status of thermal sensors)
  • toshiba_acpi (useful for Toshiba laptops)
  • video (status of video devices)

complete list of your running kernel:

$ ls -l /usr/lib/modules/$(uname -r)/kernel/drivers/acpi
total 112
-rw-r--r-- 1 root root  2808 Aug 29 23:58 ac.ko.gz
-rw-r--r-- 1 root root  3021 Aug 29 23:58 acpi_ipmi.ko.gz
-rw-r--r-- 1 root root  3354 Aug 29 23:58 acpi_memhotplug.ko.gz
-rw-r--r-- 1 root root  4628 Aug 29 23:58 acpi_pad.ko.gz
drwxr-xr-x 2 root root  4096 Aug 29 23:59 apei
-rw-r--r-- 1 root root  7120 Aug 29 23:58 battery.ko.gz
-rw-r--r-- 1 root root  3700 Aug 29 23:58 button.ko.gz
-rw-r--r-- 1 root root  2181 Aug 29 23:58 container.ko.gz
-rw-r--r-- 1 root root  1525 Aug 29 23:58 custom_method.ko.gz
-rw-r--r-- 1 root root  1909 Aug 29 23:58 ec_sys.ko.gz
-rw-r--r-- 1 root root  2001 Aug 29 23:58 fan.ko.gz
-rw-r--r-- 1 root root  1532 Aug 29 23:58 hed.ko.gz
-rw-r--r-- 1 root root  3241 Aug 29 23:58 pci_slot.ko.gz
-rw-r--r-- 1 root root 17742 Aug 29 23:58 processor.ko.gz
-rw-r--r-- 1 root root  3073 Aug 29 23:58 sbshc.ko.gz
-rw-r--r-- 1 root root  7098 Aug 29 23:58 sbs.ko.gz
-rw-r--r-- 1 root root  6311 Aug 29 23:58 thermal.ko.gz
-rw-r--r-- 1 root root  8891 Aug 29 23:58 video.ko.gz

How to select the correct ones

You have to try yourself which module works for your machine:

# modprobe <yourmodule>

then check if the module is supported on your hardware by using

$ dmesg
Tip: It may help to add a grep text search to narrow your results.
$ dmesg | grep acpi
[    0.000000] ACPI: LAPIC (acpi_id[0x00] lapic_id[0x00] enabled)
[    0.000000] ACPI: LAPIC (acpi_id[0x01] lapic_id[0x04] enabled)
[    0.000000] ACPI: LAPIC (acpi_id[0x02] lapic_id[0x01] enabled)
[    0.000000] ACPI: LAPIC (acpi_id[0x03] lapic_id[0x05] enabled)
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x00] high edge lint[0x1])
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x01] high edge lint[0x1])
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x02] high edge lint[0x1])
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x03] high edge lint[0x1])
[    5.066752] ACPI: acpi_idle yielding to intel_idle
[    5.438998] acpi device:04: registered as cooling_device4

Add the working ones to configuration files in /etc/modules-load.d. /etc/modules-load.d is described in Kernel modules#Automatic module handling.

Getting information

To read out battery information, you can simply install the package acpi in the official repositories and run:

acpi -i

Using /proc to store ACPI information has been discouraged and deprecated since Linux 2.6.24. The same data is available in /sys now, and interested parties can (should) subscribe to ACPI events from the kernel via netlink. For example, for battery:

/sys/class/power_supply/BAT0/

Troubleshooting

DSDT fix

If problems with power management persist despite having loaded the proper modules, a Linux-unfriendly DSDT might be the cause. See the wiki article on DSDT.

ACPI fix for notebooks

Sometimes you see "ACPI: EC: input buffer is not empty, aborting transaction". This is a problem with ACPI, more specifically an incompatibility of the BIOS. There may be four ways to solve this issue:

  • If available, update the BIOS.
  • Use acpi=off as kernel parameter, however this will kill all ACPI functionality like battery charging and power saving.
  • In some cases disabeling DPMS has been reported to solve the issue [1]. However, screen brightness may no longer be fully controllable:
$ xset dpms force off

See also