SMAPI support for Linux

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Revision as of 14:26, 10 December 2005 by Ajunge (Talk | contribs) (Using the <tt>thinkpad</tt> module)
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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 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 implemented functionality is control of 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), and control of CD/DVD speed.

To compile and load the module:

# tar xzvf tp_smapi-0.08.tgz
# cd tp_smapi-0.08
# make load

To install permanently (optional):

# make install
# modprobe tp_smapi

To set the thresholds for starting and stopping battery charging (in percent of current full charge capacity):

# 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

To control the speed of the optical drive:

Changing the CD speed simultaneously with a read or write to the CD will hang your computer. The hdparm -E or eject -x commands might also work for you, and are safer (but have no effect on some models, such as ThinkPad 43).
Kernel hackers: if you know how to obtain locks that temporarily prevents the ide and ata_piix+libata drivers from touching the drive, or at least how to check whether an ATAPI device is being accessed, please tell the author.
# echo 0 > /sys/devices/platform/smapi/cdrom_speed # slow
# echo 1 > /sys/devices/platform/smapi/cdrom_speed # medium
# echo 2 > /sys/devices/platform/smapi/cdrom_speed # fast
# cat /sys/devices/platform/smapi/cdrom_speed

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 and fan control. See the included README file for more information.

Model-specific status

  • ThinkPad T43, T43p, R52
    • all works
  • ThinkPad X41
    • work: all battery-related
    • unknown: cdrom_speed
  • ThinkPad G41
    • work: start_charge_thresh, inhbit_charge_minutes, cdrom_speed
    • don't work: stop_charge_thresh (not supported by hardware)
  • ThinkPad T42p, T41, R51, X40
    • work: start_charge_thresh, inhbit_charge_minutes
    • don't work: stop_charge_thresh (not supported by hardware)
    • unknown: cdrom_speed
  • ThinkPad T42
    • work: start_charge_thresh, cdrom_speed
    • unknown: inhbit_charge_minutes, stop_charge_thresh
  • ThinkPad T41p, T40p, R50p, R40, T40
    • work: cdrom_speed
    • don't work: all battery-related (not supported by hardware)
  • ThinkPad X31
    • don't work: all battery-related (not supported by hardware)
    • unknown: cdrom_speed

Please update the above and report your experience on the discussion page. If the module loads but gives a "not supported" or "not implementeded" when you try to use some specific file in /sys/devices/platform/smapi/, please report the dmesg output and whether the corresponding functionality is available under Windows - maybe your ThinkPad just can't do that.

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 Linux kernel 2.6.3 and newer you need tpctl >=4.14 and thinkpad >=5.5. For details, see the README and list of supported models.