Tp smapi

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The tp_smapi kernel module exposes some features of the ThinkPad hardware/firmware via a sysfs interface. Currently, the main implemented functionality is control of battery charging and extended battery status. The underlying hardware interfaces are SMAPI and direct access to the embedded controller.

For older ThinkPad models, see also tpctl.

This driver uses undocumented features and direct hardware access. It thus cannot be guaranteed to work and could conceivably damage your computer (though so far no incidents have been reported).


  • Battery charge/discharge control
  • Battery status information

Project Homepage / Availability


Installation from source

You will need the kernel headers and makefiles corresponding to your current kernel version. On Fedora, this means # yum install kernel-devel-$(uname -r) .

For testing, you can simply compile and load the driver within the current working directory:

# tar xzvf tp_smapi-0.32.tgz
# cd tp_smapi-0.32
# make load

To compile and install into the kernel's module path:

# make install

If you use the HDAPS driver, add HDAPS=1 to also patch the hdaps for compatibility with tp_smapi (this requires a kernel source tree matching the current kernel):

# make load HDAPS=1

or, to compile and install into the kernel's module path:

# make install HDAPS=1

To prepare a stand-alone patch against the current kernel tree (including a patch against hdaps and new Kconfig entries):

# make patch

To delete all autogenerated files:

# make clean

The original kernel tree is never modified by any these commands. The /lib/modules directory is modified only by # make install.

Comment: I had to install the complete kernel source tree to make it work (Edgy, T43)

Installation in Gentoo

The Gentoo portage system carries a tp_smapi package, which follows the latest version pretty closely. On a Gentoo system, you can install and load as follows.

If you use the HDAPS driver, do this first:

  • Configure hdaps as module in your kernel
  • Add the HDAPS use flag in /etc/make.conf
  • # rmmod hdaps


  • # emerge tp_smapi (or install tp_smapi with hdaps support manually, as above)
  • # echo "tp_smapi" >> /etc/modules.autoload.d/kernel-2.6
  • # echo "hdaps" >> /etc/modules.autoload.d/kernel-2.6

Then reboot, or run:

  • # modprobe tp_smapi
  • # modprobe hdaps

Installation on Ubuntu/Debian

Installation on Ubuntu or Debian is quite easy, but there are a few things to look after:

To get your system ready for compiling code, install the build-essentials (as root, of course, as all of the following comands; Ubuntu users have to prepend 'sudo' to every line and enter their own password when prompted):

apt-get install build-essentials

To get tp_smapi to work, obtain the latest source as mentioned above and unpack it. If you want to use HDAPS, you need to install the kernel source matching te kernel you are running. To do so, issue this:

uname -r

This will give you the version of your current kernel. As Ubuntu adds '-generic' to the kernel-version, the following command works for Debian users only:

apt-get install linux-source-`uname -r`

Ubuntu users use the kernel-version they got by the command before, e.g. 'linux-source-2.6.20'

Now change to the tp_smapi dir:

cd tp_smapi-X.YY

(X.YY being the version-number of tp_smapi)

and make and install tp_smapi as instructed above.

If you get an error that the kernel version isn't matching, please check that there is a symlink from the modules dir to the kernel source:

root@localhost:~#ls -l /lib/modules/2.6.20-6-generic
lrwxrwxrwx  1 root root     28 2007-02-02 08:39 source -> /usr/src/linux-source-2.6.20

Create the link if the line above is not existent:

root@localhost:~#ln -s /usr/src/linux-source-2.6.20 /lib/modules/2.6.20-6-generic/source

Now the following will build and install the correct modules to their locations:

make install HDAPS=1

To make sure your system loads the modules at boot time, do this:

echo "tp_smapi" >> /etc/modules
echo "hdaps" >> /etc/modules

and update your initramfs:

update-initramfs -u

To get tp_smapi running now, just load the modules:

modprobe tp_smapi hdaps

This description was tested on Kubuntu 'Feisty Fawn' and should work on all Debian-based distros with minor tweaks.

Battery charge control features

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

# echo 40 > /sys/devices/platform/smapi/BAT0/start_charge_thresh
# echo 70 > /sys/devices/platform/smapi/BAT0/stop_charge_thresh
# cat /sys/devices/platform/smapi/BAT0/*_charge_thresh
Battery charging thresholds can be used to keep Li-Ion ad Li-Polymer batteries partially charged, in order to increase their lifetime.

To unconditionally inhibit charging for 17 minutes:

# echo 17 > /sys/devices/platform/smapi/BAT0/inhibit_charge_minutes
Charge inhibiting can be used to reduce the power draw of the laptop, in order to use an under-spec power supply that can't handle the combined power draw of running and charging. It can also be used to control which battery is charged when using an Ultrabay battery.

To cancel charge inhibiting:

# echo 0 > /sys/devices/platform/smapi/BAT0/inhibit_charge_minutes

To force battery discharging even if connected to AC, use one of these:

# echo 1 > /sys/devices/platform/smapi/BAT0/force_discharge
This can be used to choose which battery is discharged when using an UltraBay battery.

To cancel forced discharge:

# echo 0 > /sys/devices/platform/smapi/BAT0/force_discharge

Battery status features

To view extended battery status such as charging state, voltage, current, capacity, cycle count and model information:

# cat /sys/devices/platform/smapi/BAT0/installed
# cat /sys/devices/platform/smapi/BAT0/state       # idle/charging/discharging
# cat /sys/devices/platform/smapi/BAT0/cycle_count
# cat /sys/devices/platform/smapi/BAT0/current_now # instantaneous current
# cat /sys/devices/platform/smapi/BAT0/current_avg # last minute average
# cat /sys/devices/platform/smapi/BAT0/power_now   # instantaneous power
# cat /sys/devices/platform/smapi/BAT0/power_avg   # last minute average
# cat /sys/devices/platform/smapi/BAT0/last_full_capacity
# cat /sys/devices/platform/smapi/BAT0/remaining_percent
# cat /sys/devices/platform/smapi/BAT0/remaining_running_time
# cat /sys/devices/platform/smapi/BAT0/remaining_charging_time
# cat /sys/devices/platform/smapi/BAT0/remaining_capacity
# cat /sys/devices/platform/smapi/BAT0/design_capacity
# cat /sys/devices/platform/smapi/BAT0/voltage
# cat /sys/devices/platform/smapi/BAT0/design_voltage
# cat /sys/devices/platform/smapi/BAT0/manufacturer
# cat /sys/devices/platform/smapi/BAT0/model
# cat /sys/devices/platform/smapi/BAT0/barcoding
# cat /sys/devices/platform/smapi/BAT0/chemistry
# cat /sys/devices/platform/smapi/BAT0/serial
# cat /sys/devices/platform/smapi/BAT0/manufacture_date
# cat /sys/devices/platform/smapi/BAT0/first_use_date
# cat /sys/devices/platform/smapi/BAT0/temperature # in milli-Celsius
# cat /sys/devices/platform/smapi/ac_connected

The raw status data is also available, including some fields not listed above (in case you can figure them out):

# cat /sys/devices/platform/smapi/BAT0/dump

In all of the above, replace BAT0 with BAT1 to address the 2nd battery.

Note that the battery status readout conflicts with the stock hdaps driver, so if you use hdaps you will need to load tp_smapi using # make load HDAPS=1 (see Bundled hdaps driver below).

On ACPI-enabled systems, most of above information is also available through the files under /proc/acpi/battery. However, the ACPI interface does not include the instantaneous power and cycle count readouts, and does not work well when hotswapping UltraBay batteries.

Other features

There is also sysfs attribute for making direct SMAPI requests to the SM BIOS firmware. Don't touch it unless you really know what you're doing. Example:

# echo '211a 100 0 0 > /sys/devices/platform/smapi/smapi_request; cat /sys/devices/platform/smapi/smapi_request
211a 34b b2 0 0 0 'OK'

The 4b" in the 2nd value, converted to decimal is 75: the current charge stop threshold.

Bundled hdaps driver

The tp_smapi package includes a modified version of the hdaps Linux kernel driver used by the HDAPS system. To use tp_smapi and hdaps concurrently, you must use the modified version.

To build the modified version, simply append the HDAPS=1 parameter to the make command (see Installation above):

# make load HDAPS=1


# make install HDAPS=1

If you don't do that, you will not be able to load tp_smapi (and its support module thinkpad_ec) when hdaps is loaded, and vice versa. You can use rmmod to switch between these modules.

Note that some of the battery status is also visible through ACPI (/proc/acpi/battery/*), independently of tp_smapi.

The modified hdaps has several changes:

  • The hdaps driver in mainline kernels conflicts with the extended battery status (they use the same IO ports). The modified hdaps coordinates this access through the bundled thinkpad_ec driver.
  • The modified hdaps driver fixes reliability and improves support for recent ThinkPad models (*60 and newer), since unlike the mainline driver, it correctly follows the Embedded Controller communication protocol.
  • Several other improvements, such as the ability to control the polling rate.


If you get thinkpad_ec: no ThinkPad embedded controller! when trying to load the module on a supported model listed below, you should upgrade your BIOS. Some early BIOS (like 1.x on the X31) don't handle the embedded controller.

Model-specific status

tp_smapi feature support matrix
× start_charge_
force_discharge battery status files HDAPS
HDAPS axis orientation Notes
A series
A22p 2629-USG no no no no no unknown
A30 no no no no yes unknown
G series
G41 yes no yes unknown unknown unknown
R series
R31 no no no no no unknown No SMAPI BIOS
R40 no no no no unknown unknown
R50 unknown no unknown unknown yes unknown
R50e 1834-JAG yes no yes yes yes unknown
R50p no no no no yes unknown
R51 yes no yes unknown yes unknown
R52 yes yes yes yes yes yes X'=X, Y'=Y (OK with v0.32)
R60 yes yes yes yes yes yes
T series
T20 no no no no no unknown Has SMAPI BIOS but no function is supported. EC LPC3 protocol fails.
T22 no no no no no unknown Has SMAPI BIOS but no function is supported. EC LPC3 protocol fails.
T23 no no no no yes unknown
T30 no no no no yes unknown
T40 no no no unknown yes unknown
T40p no no no no yes unknown
T41 no no no no yes unknown
T41p no no no no yes unknown
T42 yes no yes yes yes unknown
T42p 2373-KUU yes no yes unknown yes unknown
T43 2686 yes yes yes yes yes yes X'=X, Y'=Y (OK with v0.32)
T43p yes yes yes yes yes unknown
T60 yes yes unknown yes yes yes X'=Y, Y'=-X (Wrong with v0.32)
X series
X20 2662-31G no no no no no unknown
X24 no no no unknown yes unknown
X31 no no no unknown yes unknown
X32 no no no no yes unknown
X40 yes yes yes unknown yes unknown BIOS v2.03, EC v1.60
X41 yes yes yes yes yes unknown
X60 yes yes yes yes yes yes BIOS v2.07, EC v1.10, 2.6.20 issue (see discussion)
Z series
Z60m yes yes yes yes yes unknown
Z60t yes yes unknown unknown yes unknown
Z61m yes yes yes yes yes yes
Z61t yes yes yes yes yes yes

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.

While at it, you may also want to add your laptop to the list of DMI IDs.

Tools using this driver

The driver's interface can be accessed directly through the files under /sys/devices/platform/smapi, or via the following tools: