ACPI_IBM(4)

📦 version 15.1, in freebsd 14.5, freebsd 15.1, nixpkgs unstable

💖 `acpi_ibm` — ThinkPad ACPI extras driver 💖

okay bestie, this is the page for ACPI_IBM(4), and we're doing a full tour of the ThinkPad ACPI extras driver. It's giving laptop-whisperer energy, no cap. 🫶

🎀 NAME 🎀

acpi_ibm — ThinkPad ACPI extras driver

🌈 SYNOPSIS 🌈

To compile this driver into the kernel, put this line in your kernel configuration file:

device acpi_ibm

Alternatively, to load the driver as a module at boot time, put this line in loader.conf(5):

acpi_ibm_load="YES"

🦋 DESCRIPTION 🦋

The acpi_ibm driver gives you support for hotkeys and other components on ThinkPad laptops. The main character purpose here is to provide an interface — accessible via sysctl(8) and devd(8) — through which applications can figure out the status of various laptop components. 💅

The sysctl(8) interface gets enabled automatically after loading the driver, but the devd(8) interface has to be enabled explicitly, because it may alter the default action of certain keys. You do that by setting the events sysctl as described below. Specifying which keys should generate events is done by setting a bitmask, where each bit represents one key or key combination. This bitmask, accessible via the eventmask sysctl, is set to availmask by default — a value representing all possible keypress events on the specific ThinkPad model. ✨

🦋 devd(8) Events

Hotkey events received by devd(8) provide the following info:

system     "ACPI"
subsystem  "IBM"
type       The source of the event in the ACPI namespace.  The
           value depends on the model.
notify     Event code (see below).

Depending on the ThinkPad model, event codes may vary. On a ThinkPad T41p these are as follows:

0x01 — Fn + F1
0x02 — Fn + F2
0x03 — Fn + F3 (LCD backlight)
0x04 — Fn + F4 (Suspend to RAM)
0x05 — Fn + F5 (Bluetooth)
0x06 — Fn + F6
0x07 — Fn + F7 (Screen expand)
0x08 — Fn + F8
0x09 — Fn + F9
0x0a — Fn + F10
0x0b — Fn + F11
0x0c — Fn + F12 (Suspend to disk)
0x0d — Fn + Backspace
0x0e — Fn + Insert
0x0f — Fn + Delete
0x10 — Fn + Home (Brightness up)
0x11 — Fn + End (Brightness down)
0x12 — Fn + PageUp (ThinkLight)
0x13 — Fn + PageDown
0x14 — Fn + Space (Zoom)
0x15 — Volume Up
0x16 — Volume Down
0x17 — Mute
0x18 — Access IBM Button

🌸 led(4) Interface

The acpi_ibm driver provides a led(4) interface for the ThinkLight. The ThinkLight can be made to blink by writing ASCII strings to the /dev/led/thinklight device. 🧚

✨ SYSCTL VARIABLES ✨

The following sysctls are currently implemented:

dev.acpi_ibm.0.initialmask — (read-only) Bitmask of ACPI events before the acpi_ibm driver was loaded.
dev.acpi_ibm.0.availmask — (read-only) Bitmask of all supported ACPI events.
dev.acpi_ibm.0.events — Enable ACPI events and set the eventmask to availmask. Without the acpi_ibm driver being loaded, only the Fn+F4 button generates an ACPI event.
dev.acpi_ibm.0.eventmask — Sets the ACPI events which are reported to devd(8). Fn+F3, Fn+F4 and Fn+F12 always generate ACPI events, regardless which value eventmask has. Depending on the ThinkPad model, the meaning of different bits in the eventmask may vary. On a ThinkPad T41p this is a bitwise OR of the following:
- 1 — Fn + F1
- 2 — Fn + F2
- 4 — Fn + F3 (LCD backlight)
- 8 — Fn + F4 (Suspend to RAM)
- 16 — Fn + F5 (Bluetooth)
- 32 — Fn + F6
- 64 — Fn + F7 (Screen expand)
- 128 — Fn + F8
- 256 — Fn + F9
- 512 — Fn + F10
- 1024 — Fn + F11
- 2048 — Fn + F12 (Suspend to disk)
- 4096 — Fn + Backspace
- 8192 — Fn + Insert
- 16384 — Fn + Delete
- 32768 — Fn + Home (Brightness up)
- 65536 — Fn + End (Brightness down)
- 131072 — Fn + PageUp (ThinkLight)
- 262144 — Fn + PageDown
- 524288 — Fn + Space (Zoom)
- 1048576 — Volume Up
- 2097152 — Volume Down
- 4194304 — Mute
- 8388608 — Access IBM Button
dev.acpi_ibm.0.hotkey — (read-only) Status of several buttons. Every time a button is pressed, the respecting bit is toggled. It is a bitwise OR of the following:
- 1 — Home Button
- 2 — Search Button
- 4 — Mail Button
- 8 — Access IBM Button
- 16 — Zoom
- 32 — Wireless LAN Button
- 64 — Video Button
- 128 — Hibernate Button
- 256 — ThinkLight Button
- 512 — Screen Expand
- 1024 — Brightness Up/Down Button
- 2048 — Volume Up/Down/Mute Button
dev.acpi_ibm.0.lcd_brightness — Current brightness level of the display.
dev.acpi_ibm.0.volume — Speaker volume.
dev.acpi_ibm.0.mute — Indicates whether the speakers are muted or not.
dev.acpi_ibm.0.mic_mute — Indicates whether the microphone led (present on some model) is on or not. Note that this does not mean that the microphone input is muted.
dev.acpi_ibm.0.thinklight — Indicates whether the ThinkLight keyboard light is activated or not.
dev.acpi_ibm.0.bluetooth — Toggle Bluetooth chip activity.
dev.acpi_ibm.0.wlan — (read-only) Indicates whether the WLAN chip is active or not.
dev.acpi_ibm.0.fan — Indicates whether the fan is in automatic (1) or manual (0) mode. Default is automatic mode.

bestie, this one is serious: this sysctl should be used with extreme precaution, since disabling automatic fan control might overheat the ThinkPad and lead to permanent damage if the fan_level is not set accordingly. 😭

dev.acpi_ibm.0.fan_level — Indicates at what speed the fan should run when being in manual mode. Valid values range from 0 (off) to 7 (max) and 8. Level 8 is used by the driver to set the fan in unthrottled mode. In this mode, the fan is set to spin freely and will quickly reach a very high speed. Use this mode only if absolutely necessary, e.g., if the system has reached its critical temperature and it is about to shut down. The resulting speed differs from model to model. On a T41p this is as follows:
- 0 — off
- 1, 2 — ~3000 RPM
- 3, 4, 5 — ~3600 RPM
- 6, 7 — ~4300 RPM
- 8 — ~6400 RPM (Full-speed, unthrottled)
dev.acpi_ibm.0.fan_speed — (read-only) Fan speed in rounds per minute. A few older ThinkPads report the fan speed in levels ranging from 0 (off) to 7 (max).
dev.acpi_ibm.0.thermal — (read-only) Shows the readings of up to eight different temperature sensors. Most ThinkPads include six or more temperature sensors but only expose the CPU temperature through acpi_thermal(4). Some ThinkPads have the below sensor layout which might vary depending on the specific model:
1. CPU
2. Mini PCI Module
3. HDD
4. GPU
5. Built-in battery
6. UltraBay battery
7. Built-in battery
8. UltraBay battery
dev.acpi_ibm.0.handlerevents — devd(8) events handled by acpi_ibm when events is set to 1. Events are specified as a whitespace-separated list of event code in hexadecimal or decimal form. Note that the event maybe handled twice (e.g., Brightness up/down) if ACPI BIOS already handled the event.

Defaults for these sysctls can be set in sysctl.conf(5).

🎀 FILES 🎀

/dev/led/thinklight — ThinkLight led(4) device node

✨ EXAMPLES ✨

okay bestie, this is where you actually make the buttons do stuff 💅 You can add this next bit to devd.conf(5) so button events get passed to a /usr/local/sbin/acpi_oem_exec.sh script:

             notify 10 {
                     match "system"          "ACPI";
                     match "subsystem"       "IBM";
                     action "/usr/local/sbin/acpi_oem_exec.sh $notify ibm";
             };

A possible /usr/local/sbin/acpi_oem_exec.sh script might look like this — yes, the whole thing, no skipped lines 😭:

             #!/bin/sh
             #
             if [ "$1" = "" -o "$2" = "" ]
             then
                     echo "usage: $0 notify oem_name"
                     exit 1
             fi
             NOTIFY=`echo $1`
             LOGGER="logger"
             CALC="bc"
             BC_PRECOMMANDS="scale=2"
             ECHO="echo"
             CUT="cut"
             MAX_LCD_BRIGHTNESS=7
             MAX_VOLUME=14
             OEM=$2
             DISPLAY_PIPE=/tmp/acpi_${OEM}_display

             case ${NOTIFY} in
                     0x05)
                             LEVEL=`sysctl -n dev.acpi_${OEM}.0.bluetooth`
                             if [ "$LEVEL" = "1" ]
                             then
                                     sysctl dev.acpi_${OEM}.0.bluetooth=0
                                     MESSAGE="bluetooth disabled"
                             else
                                     sysctl dev.acpi_${OEM}.0.bluetooth=1
                                     MESSAGE="bluetooth enabled"
                             fi
                             ;;
                     0x10|0x11)
                             LEVEL=`sysctl -n dev.acpi_${OEM}.0.lcd_brightness`
                             PERCENT=`${ECHO} "${BC_PRECOMMANDS} ; \
                                      ${LEVEL} / ${MAX_LCD_BRIGHTNESS} * 100" |\
                                      ${CALC} | ${CUT} -d . -f 1`
                             MESSAGE="brightness level ${PERCENT}%"
                             ;;
                     0x12)
                             LEVEL=`sysctl -n dev.acpi_${OEM}.0.thinklight`
                             if [ "$LEVEL" = "1" ]
                             then
                                     MESSAGE="thinklight enabled"
                             else
                                     MESSAGE="thinklight disabled"
                             fi
                             ;;
                     0x15|0x16)
                             LEVEL=`sysctl -n dev.acpi_${OEM}.0.volume`
                             PERCENT=`${ECHO} "${BC_PRECOMMANDS} ; \
                                     ${LEVEL} / ${MAX_VOLUME} * 100" | \
                                      ${CALC} | ${CUT} -d . -f 1`
                             MESSAGE="volume level ${PERCENT}%"
                             ;;
                     0x17)
                             LEVEL=`sysctl -n dev.acpi_${OEM}.0.mute`
                             if [ "$LEVEL" = "1" ]
                             then
                                     MESSAGE="volume muted"
                             else
                                     MESSAGE="volume unmuted"
                             fi
                             ;;
                     0x1b)
                             LEVEL=`sysctl -n dev.acpi_ibm.0.mic_led`
                             if [ $LEVEL -eq 0 ]; then
                                     sysctl dev.acpi_ibm.0.mic_led=1
                                     mixer rec.volume=0
                             fi
                             if [ $LEVEL -eq 1 ]; then
                                     sysctl dev.acpi_ibm.0.mic_led=0
                                     mixer rec.volume=30%
                             fi
                             ;;
                     *)
                             ;;
             esac
             ${LOGGER} ${MESSAGE}
             if [ -p ${DISPLAY_PIPE} ]
             then
                     ${ECHO} ${MESSAGE} >> ${DISPLAY_PIPE} &
             fi
             exit 0

And if you want event code 0x04 (Suspend to RAM), 0x10 (Brightness up), and 0x11 (Brightness down) to be handled by acpi_ibm, the example is literally this:

sysctl dev.acpi_ibm.0.handlerevents='0x04 0x10 0x11'

In sysctl.conf(5), that same vibe looks like:

dev.acpi_ibm.0.handlerevents=0x04\ 0x10\ 0x11

🔗 SEE ALSO 🔗

🦋 HISTORY 🦋

The acpi_ibm device driver first appeared in FreeBSD 6.0 — vintage but iconic ✨

👑 AUTHORS 👑

The acpi_ibm driver was written by Takanori Watanabe <takawata@FreeBSD.org> and later mostly rewritten by Markus Brueffer <markus@FreeBSD.org>. This manual page was written by Christian Brueffer <brueffer@FreeBSD.org> and Markus Brueffer <markus@FreeBSD.org>. Give them their flowers, fr fr 💐

that's the whole page, bestie 🫶 it's from the Debian crew, dated March 13, 2022, and the page is literally ACPI_IBM(4) — slay ✨

📦 where this page comes from

freebsd 14.5: base 14.5
freebsd 15.1: base 15.1
nixpkgs unstable: source
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms