Tp smapi

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tp_smapi is a set of kernel modules that retrieves information from and conveys commands to the hardware of ThinkPad laptops. This information is presented through the /sys/devices/platform/smapi filesystem. Much like the /proc filesystem, you can read and write information to these files to get information about and send commands to the hardware. tp_smapi is highly recommended if you're using a ThinkPad laptop.


Install tp_smapi from AUR. After installing, add tp_smapi to your MODULES array. After a reboot, this will activate most of the drivers, represented through the /sys/devices/platform/smapi filesystem.


Here are a couple of useful things you can do using tp_smapi. Please feel free to add your own.

Control Battery Charging

It's bad for most laptop batteries to hold a full charge for long periods of time. You should try to keep your battery in the 40-80% charged range, unless you need the battery life for extended periods of time. tp_smapi lets you control the start and stop charging threshold to do just that. Run these commands to set these to good values:

echo 40 > /sys/devices/platform/smapi/BAT0/start_charge_thresh
echo 80 > /sys/devices/platform/smapi/BAT0/stop_charge_thresh

This will cause the battery to begin charging when it falls below 40% charge and stop charging once it exceeds 80% charge. This will extend the lifetime of your battery.

Note that when you remove and re-insert the battery, these thresholds may be reset to their default values. To work around this, create a script to set these values, and make this script run both at startup and when a battery is inserted. More specific instructions follow.

Create a script /usr/sbin/set_battery_thresholds:

# set the battery charging thresholds to extend battery lifespan
echo 40 > /sys/devices/platform/smapi/BAT0/start_charge_thresh
echo 80 > /sys/devices/platform/smapi/BAT0/stop_charge_thresh

Set it runnable:

[root ~]# chmod 744 /usr/sbin/set_battery_threshold

Make this script run at startup by editing /etc/rc.local:

#... other rc.local stuff

Make it run when a battery is inserted. This requires that acpid is installed and running. Edit /etc/acpi/

#... other ACPI stuff
  case "$2" in
      case "$4" in
#... more ACPI stuff

Protect the Hard Disk from Drops

tp_smapi includes a driver to read the accelerometer in your laptop to detect drops and other events that could cause damage to your hard drive. See the HDAPS page for more information on this useful feature.

See Also

tp_smapi on ThinkWiki