Tp smapi

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The tp_smapi kernel module exposes some features of the SMAPI interface found on recent ThinkPads via a sysfs interface. Currently, the implemented functionality is control of battery charging, extended battery status and control of CD/DVD speed (disabled by default).

For old ThinkPad models, see also tpctl.

This driver uses undocumented features and direct hardware access. They thus cannot be guaranteed to work, and may cause arbitrary damage (though so far none was reported)..


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

# tar xzvf tp_smapi-0.15.tgz
# cd tp_smapi-0.15
# 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):

# make load HDAPS=1   or   # make install HDAPS=1

To prepare a stand-alone patch against the current kernel tree (including a compatibility fixes to hdaps and 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.

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 a 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_discharge1
This can be used to choose which battery is discharged when using an UltraBay battery.

To cancel forced discharge, use one of these:

# echo 0 > /sys/devices/platform/smapi/BAT0/force_discharge1
# echo 0 > /sys/devices/platform/smapi/BAT0/force_discharge2

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_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/serial
# cat /sys/devices/platform/smapi/BAT0/barcoding
# cat /sys/devices/platform/smapi/BAT0/chemistry
# 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 Conflict with hdaps below).

Optical drive control features

To control the speed of the optical drive:

# echo 0 > /sys/devices/platform/smapi/cd_speed # slow
# echo 1 > /sys/devices/platform/smapi/cd_speed # medium
# echo 2 > /sys/devices/platform/smapi/cd_speed # fast
# cat /sys/devices/platform/smapi/cd_speed
Enabling this feature

Changing the drive speed when a disc is being accessed will hang your computer. This feature is thus disabled by default, but can be enabled using by adding #define PROVIDE_CD_SPEED at the top of tp_smapi.c. The safe way to set the drive speed is using hdparm -E num or eject -x num for CD-ROM, and speedcontrol -x num (sourcecode here) for DVD. For kernels older than 2.6.15, this may require the libata pass-through patch.

Other features

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

Conflict with hdaps

The extended battery status function conflicts with the hdaps kernel module (they use the same IO ports).

You can use HDAPS=1 (see Installation) to get a patched version of hdaps which is compatible with tp_smapi.


If you load hdaps first, tp_smapi will disable its battery status functions (and log a message in the kernel log). If you load tp_smapi first, hdaps will refuse to load. To switch between the two, rmmod both and then load one you need.

Some of the battery status is also visible through ACPI (/proc/acpi/battery/*).

The charging control files (*_charge_thresh, inhibit_charge_minutes and force_discharge*) don't have this problem.

Model-specific status

tp_smapi feature support matrix
× start_charge_
(see [[#Enabling_this_feature|note] above)
battery status files
(see note about hdaps above)
G41 yes no yes yes unknown unknown unknown
R40 no no no yes unknown unknown unknown
R50p no no no yes no no yes
R51 yes no yes unknown unknown unknown yes
R52 yes yes yes yes unknown unknown unknown
T23 no no no unknown no no yes
T40 no no no yes unknown unknown yes
T40p no no no yes no no yes
T41 no no no yes no no yes
T41p no no no yes unknown unknown unknown
T42 yes no yes yes yes no yes
T42p yes no yes unknown unknown unknown unknown
T43 yes yes yes yes yes no yes
T43p yes yes yes yes yes no yes
X24 no no no unknown unknown unknown yes
X31 no no no unknown unknown unknown yes
X32 no no no unknown unknown unknown unknown
X40 yes no yes unknown unknown unknown yes
X41 yes yes yes unknown yes no 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.