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README.md

acpi_call

This is a fork of acpi_call maintained by the NixOS community. Patches also for non-NixOS related fixes are welcome!

A simple kernel module that allows one to call ACPI methods by writing the method name followed by its arguments to /proc/acpi/call.

Notes on dkms and Secure Boot

If that is the way you want to install this module, you can follow this guide to have dkms automatically sign the module after building.

Usage

echo '<call>' | sudo tee /proc/acpi/call

You can then retrieve the result of the call by checking your dmesg or:

sudo cat /proc/acpi/call

An example to turn off the discrete graphics card in a dual graphics environment (like NVIDIA Optimus):

# turn off discrete graphics card
echo '\_SB.PCI0.PEG1.GFX0.DOFF' > /proc/acpi/call
# turn it back on
echo '\_SB.PCI0.PEG1.GFX0.DON' > /proc/acpi/call

These work on my ASUS K52J notebook, but may not work for you. For a list of methods to try, see http://linux-hybrid-graphics.blogspot.com/ or try running the provided script examples/turn_off_gpu.sh

It SHOULD be ok to test all of the methods, until you see a drop in battery drain rate (grep rate /proc/acpi/battery/BAT0/state), however it comes with NO WARRANTY - it may hang your computer/laptop, fail to work, etc.

You can pass parameters to acpi_call by writing them after the method, separated by single space. Currently, you can pass the following parameter types:

  • ACPI_INTEGER - by writing NNN or 0xNNN, where NNN is an integer/hex
  • ACPI_STRING - by enclosing the string in quotes: "hello, world"
  • ACPI_BUFFER - by writing bXXXX, where XXXX is a hex string without spaces, or by writing { b1, b2, b3, b4 }, where b1-4 are integers

The status after a call can be read back from /proc/acpi/call:

  • 'not called' - nothing to report
  • 'Error: ' - the call failed
  • '0xNN' - the call succeeded, and returned an integer
  • '"..."' - the call succeeded, and returned a string
  • '{0xNN, ...}' - the call succeeded, and returned a buffer
  • '[...]' - the call succeeded, and returned a package which may contain the above types (integer, string and buffer) and other package types

GUI Alternatives

Found this too difficult? Try to use these programs provided by Marco Dalla Libera and do it via graphic interface. Note that they is not suitable for arbitrary APCI calls but intended for turning off discrete graphics only.


Copyright (c) 2010: Michal Kottman

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

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A linux kernel module that enables calls to ACPI methods through /proc/acpi/call. [maintainer=@teleshoes /@Mic92]

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