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A linux kernel module that enables calls to ACPI methods through /proc/acpi/call. Now with support for Integer, String and Buffer parameters.
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README.md
acpi_call.c

README.md

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

This module is to be considered a proof-of-concept and has been superseeded by projects like bbswitch. It allows you to tamper with your system and should be used with caution.

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 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

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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