SMAPI support for Linux

ThinkPad laptops include a proprietary interface called SMAPI BIOS (System Management Application Program Interface) which provides some hardware control functionality that is not exposed by any other interface (e.g., ACPI).

The SMAPI interfaces changes a lot between models, and is poorly documented, so Linux support is not exhaustive for most models. There currently two SMAPI interfaces available: tpctl for older ThinkPads, and tp_smapi for newer ones.

ATTENTION!

This driver uses undocumented features and direct hardware access. They thus cannot be guaranteed to work, and may cause arbitrary damage (especially on models they weren't tested on).

Using tpctl and thinkpad

This solution consists of a module, called thinkpad, and a user-space tool caled tpctl. It provides very rich functionality for older ThinkPads, but on newer ThinkPads much of this functionality is exposed and supported through an ACPI interface and the SMAPI access does not work anymore. For details, see the README and list of supported models.

Project page: http://tpctl.sourceforge.net/

Using tp_smapi

The tp_smapi kernel module uses the current SMAPI interface to expose some features of the SMAPI BIOS via a sysfs interface. Currently, the only implemented functionality is setting the battery charge start and stop thresholds (this is useful for increasing battery lifetime). The module has been posted here.

To download the current version from the linux-thinkpad list archives:

# wget -O - http://mailman.linux-thinkpad.org/pipermail/linux-thinkpad/2005-December/030802.html |
  perl -MMIME::Base64 -ne '$a=!$a if m/^---/; next if !$a; $a++ if m/^$/; print decode_base64($_) if $a>1'  > tp_smapi-0.02.tgz

To compile and load the module:

# tar xzvf tp_smapi-0.02.tgz
# cd tp_smapi-0.01
# make load

To install permanently (optional):

# make install
# modprobe tp_smapi

Example of usage:

# echo 40 > /sys/devices/platform/smapi/start_charge_thresh
# echo 70 > /sys/devices/platform/smapi/stop_charge_thresh
# cat /sys/devices/platform/smapi/*_charge_thresh
40 
70

Other things that can be controlled through SMAPI, but are not supported in this version of the driver, include forcing battery discharge, disallowing battery charging, PCI bus power saving, CPU power saving control, extended smart battery information and fan control. See the exported symbols in PWRMGRIF.DLL for more hints.

Models on which this driver works fully

• ThinkPad T43

Models which have a SMAPI BIOS which do not support battery charge thresholds

• ThinkPad R40, T40p, G41 (not yet verified).

Please update the above and report your experience on the discussion page.