SMAPI support for Linux

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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 are currently two SMAPI access mechanisms available: thinkpad and tpctl for older ThinkPads, and tp_smapi for newer ones.

These drivers use 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 the thinkpad module

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.

Using the tp_smapi module

The tp_smapi kernel module exposes some features of the SMAPI BIOS found on recent ThinkPads via a sysfs interface. Currently, the only implemented functionality is control over battery charging (this is useful for increasing battery lifetime, or for using a leftover under-spec power supply that can't handle the combined power draw of running and charging).

To compile and load the module:

# tar xzvf tp_smapi-0.06.tgz
# cd tp_smapi-0.06
# 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

To unconditionally inhibit charging for 17 minutes:

# echo 17 > /sys/devices/platform/smapi/inhibit_charge_minutes

To cancel charge inhibiting:

# echo 0 > /sys/devices/platform/smapi/inhibit_charge_minutes

If you get a "not supported" error, your laptop doesn't provide the specific function (or at least not via SMAPI).

Other things that can be controlled through SMAPI, but are not supported in this version of the driver, include forcing battery discharge, PCI bus power saving, CPU power saving control, extended smart battery information, CD/DVD drive speed control and fan control. See the included README file for more information.

Models on which this driver works

For the details, see the README file inside the package. If you have new data, please report it on the discussion page.

Models on which none of the functions work

  • ThinkPad T40, T40p, R50p, R40, X31 and probably all earlier models. These apparently don't have the relevant capabilities, even under Windows.

Please update the above and report your experience on the discussion page. If the module loads but gives "not supported" errors when you try to use it, report whether the corresponding functionality is available under Windows - maybe your ThinkPad just can't do that.