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tp_smapi version 0.41
IBM ThinkPad hardware functions driver

Author:  Shem Multinymous <>


ThinkPad laptops include a proprietary interface called SMAPI BIOS
(System Management Application Program Interface) which provides some
hardware control functionality that is not accessible by other means.

This driver exposes some features of the SMAPI BIOS through a sysfs
interface. It is suitable for newer models, on which SMAPI is invoked
through IO port writes. Older models use a different SMAPI interface;
for those, try the "thinkpad" module from the "tpctl" package.

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


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

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

If you use the HDAPS driver, use these instead to replace the hdaps module
with one patched for compatibility with tp_smapi:
# make load HDAPS=1
# make install HDAPS=1

With some recent ThinkPad models, the "thinkpad_ec" will refuse to load due to
reserved ports. You can force loading by passing the "force_io=1" parameter
to the "thinkpad_ec" module using /etc/modules.conf (or your distribution's
equivalent). To test this prior to installation, use:
# make load HDAPS=1 FORCE_IO=1

To prepare a stand-alone patch against the current kernel tree (including
the hdaps replacement and Kconfig entries), assuming you have its sourcecode
under /lib/modules/`uname -r`/source:
# make patch

To work against a kernel (other than the current one) that's properly
installed under /lib/modules/*, add an appropriate KVER= parameter
# make patch KVER=2.6.16
To work against another kernel, you'll need to set KSRC and KBUILD too:
# make patch KVER=2.6.16 KSRC=$HOME/2.6.16 KBUILD=$HOME/2.6.16

To delete all autogenerated files:
# make clean

Append "DEBUG=1" to "make load" to load tp_smapi with debug=1.

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

Module parameters

thinkpad_ec module:
  force_io=1 lets thinkpad_ec load on some recent ThinkPad models
  (e.g., T400 and T500) whose BIOS's ACPI DSDT reserves the ports we need.
tp_smapi module:
  debug=1    enables verbose dmesg output.


Control of battery charging thresholds (in percents of current full charge

# 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

    (This is useful since Li-Ion batteries wear out much faster at very
     high or low charge levels. The driver will also keeps the thresholds
     across suspend-to-disk with AC disconnected; this isn't done
     automatically by the hardware.)

Inhibiting battery charging for 17 minutes (overrides thresholds):

# echo 17 > /sys/devices/platform/smapi/BAT0/inhibit_charge_minutes
# echo 0  > /sys/devices/platform/smapi/BAT0/inhibit_charge_minutes  # stop
# cat /sys/devices/platform/smapi/BAT0/inhibit_charge_minutes

    (This can be used to control which battery is charged when using an
     Ultrabay battery.)

Forcing battery discharging even if AC power available:

# echo 1 > /sys/devices/platform/smapi/BAT0/force_discharge  # start discharge
# echo 0 > /sys/devices/platform/smapi/BAT0/force_discharge  # stop discharge
# cat /sys/devices/platform/smapi/BAT0/force_discharge

    (When AC is connected, forced discharging will automatically stop
     when battery is fully depleted -- this is useful for calibration.
     Also, this attribute can be used to control which battery is discharged
     when both a system battery and an Ultrabay battery are connected.)

Misc read-only battery status attributes (see note about HDAPS below):

/sys/devices/platform/smapi/BAT0/installed   # 0 or 1
/sys/devices/platform/smapi/BAT0/state       # idle/charging/discharging
/sys/devices/platform/smapi/BAT0/cycle_count # integer counter
/sys/devices/platform/smapi/BAT0/current_now # instantaneous current
/sys/devices/platform/smapi/BAT0/current_avg # last minute average
/sys/devices/platform/smapi/BAT0/power_now   # instantaneous power
/sys/devices/platform/smapi/BAT0/power_avg   # last minute average
/sys/devices/platform/smapi/BAT0/last_full_capacity         # in mWh
/sys/devices/platform/smapi/BAT0/remaining_percent          # remaining percent of energy (set by calibration)
/sys/devices/platform/smapi/BAT0/remaining_percent_error    # error range of remaing_percent (not reset by calibration)
/sys/devices/platform/smapi/BAT0/remaining_running_time     # in minutes, by last minute average power
/sys/devices/platform/smapi/BAT0/remaining_running_time_now # in minutes, by instantenous power
/sys/devices/platform/smapi/BAT0/remaining_charging_time    # in minutes
/sys/devices/platform/smapi/BAT0/remaining_capacity         # in mWh
/sys/devices/platform/smapi/BAT0/design_capacity            # in mWh
/sys/devices/platform/smapi/BAT0/voltage           # in mV
/sys/devices/platform/smapi/BAT0/design_voltage    # in mV
/sys/devices/platform/smapi/BAT0/charging_max_current  # max charging current
/sys/devices/platform/smapi/BAT0/charging_max_voltage  # max charging voltage
/sys/devices/platform/smapi/BAT0/group{0,1,2,3}_voltage # see below
/sys/devices/platform/smapi/BAT0/manufacturer      # string
/sys/devices/platform/smapi/BAT0/model             # string
/sys/devices/platform/smapi/BAT0/barcoding         # string
/sys/devices/platform/smapi/BAT0/chemistry         # string
/sys/devices/platform/smapi/BAT0/serial            # integer
/sys/devices/platform/smapi/BAT0/manufacture_date  # YYYY-MM-DD
/sys/devices/platform/smapi/BAT0/first_use_date    # YYYY-MM-DD
/sys/devices/platform/smapi/BAT0/temperature  # in milli-Celsius
/sys/devices/platform/smapi/BAT0/dump         # see below
/sys/devices/platform/smapi/ac_connected      # 0 or 1

The BAT0/group{0,1,2,3}_voltage attribute refers to the separate cell groups
in each battery. For example, on the ThinkPad 600, X3x, T4x and R5x models,
the battery contains 3 cell groups in series, where each group consisting of 2
or 3 cells  connected in parallel. The voltage of each group is given by these
attributes, and their sum (roughly) equals the "voltage" attribute.
(The effective performance of the battery is determined by the weakest group,
i.e., the one those voltage changes most rapidly during dis/charging.)

The "BAT0/dump" attribute gives a a hex dump of the raw status data, which
contains additional data now in the above (if you can figure it out). Some
unused values are autodetected and replaced by "--":

In all of the above, replace BAT0 with BAT1 to address the 2nd battery (e.g.
in the UltraBay).

Raw SMAPI calls:

This performs raw SMAPI calls. It uses a bad interface that cannot handle
multiple simultaneous access. Don't touch it, it's for development only.
If you did touch it, you would so something like
# echo '211a 100 0 0' > /sys/devices/platform/smapi/smapi_request
# cat /sys/devices/platform/smapi/smapi_request
and notice that in the output "211a 34b b2 0 0 0 'OK'", the "4b" in the 2nd
value, converted to decimal is 75: the current charge stop threshold.

Model-specific status

Works (at least partially) on the following ThinkPad model:
* A30
* G41
* R40, R50p, R51, R52
* T23, T40, T40p, T41, T41p, T42, T42p, T43, T43p, T60
* X24, X31, X32, X40, X41, X60
* Z60t, Z61m

Not all functions are available on all models; for detailed status, see:

Please report success/failure by e-mail or on the Wiki.
If you get a "not implemented" or "not supported" message, your laptop
probably just can't do that (at least not via the SMAPI BIOS).
For negative reports, follow the bug reporting guidelines below.
If you send me the necessary technical data (i.e., SMAPI function
interfaces), I will support additional models.

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 these 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_discrage*) don't have this problem.

Additional HDAPS features

The modified hdaps driver has several improvements on the one in mainline
(beyond resolving the conflict with thinkpad_ec and tp_smapi):

- Fixes reliability and improves support for recent ThinkPad models
  (especially *60 and newer). Unlike the mainline driver, the modified hdaps
  correctly follows the Embedded Controller communication protocol.

- Extends the "invert" parameter to cover all possible axis orientations.
  The possible values are as follows.
  Let X,Y denote the hardware readouts.
  Let R denote the laptop's roll (tilt left/right).
  Let P denote the laptop's pitch (tilt forward/backward).
    invert=0:   R= X  P= Y   (same as mainline)
    invert=1:   R=-X  P=-Y   (same as mainline)
    invert=2:   R=-X  P= Y   (new)
    invert=3:   R= X  P=-Y   (new)
    invert=4:   R= Y  P= X   (new)
    invert=5:   R=-Y  P=-X   (new)
    invert=6:   R=-Y  P= X   (new)
    invert=7:   R= Y  P=-X   (new)
  It's probably easiest to just try all 8 possibilities and see which yields
  correct results (e.g., in the hdaps-gl visualisation).

- Adds a whitelist which automatically sets the correct axis orientation for
  some models. If the value for your model is wrong or missing, you can override
  it using the "invert" parameter. Please also update the tables at and
  and submit a patch for the whitelist in hdaps.c.

- Provides new attributes:
    This determines the frequency at which the host queries the embedded
    controller for accelerometer data (and informs the hdaps input devices).
    When set to X, the embedded controller is told to do physical accelerometer
    measurements at a rate that is X times higher than the rate at which
    the driver reads those measurements (i.e., X*sampling_rate). This
    makes the readouts from the embedded controller more fresh, and is also
    useful for the running average filter (see next). Default=5
    When set to X, reported readouts will be the average of the last X physical
    accelerometer measurements. Current firmware allows 1<=X<=8. Setting to a
    high value decreases readout fluctuations. The averaging is handled by the
    embedded controller, so no CPU resources are used. Higher values make the
    readouts smoother, since it averages out both sensor noise (good) and abrupt
    changes (bad). Default=2.

- Provides a second input device, which publishes the raw accelerometer
  measurements (without the fuzzing needed for joystick emulation). This input
  device can be matched by a udev rule such as the following (all on one line):
    KERNEL=="event[0-9]*", ATTRS{phys}=="hdaps/input1",

A new version of the hdapsd userspace daemon, which uses the input device
interface instead of polling sysfs, is available seprately. Using this reduces
the total interrupts per second generated by hdaps+hdapsd (on tickless kernels)
to 50, down from a value that fluctuates between 50 and 100. Set the
sampling_rate sysfs attribute to a lower value to further reduce interrupts,
at the expense of response latency.

Licensing note: all my changes to the HDAPS driver are licensed under the
GPL version 2 or, at your option and to the extent allowed by derivation from
prior works, any later version. My version of hdaps is derived work from the
mainline version, which at the time of writing is available only under
GPL version 2.

Bug reporting

Mail <>. Please include:
* Details about your model,
* Relevant "dmesg" output. Make sure thinkpad_ec and tp_smapi are loaded with
  the "debug=1" parameter (e.g., use "make load HDAPS=1 DEBUG=1").
* Output of "dmidecode | grep -C5 Product"
* Does the failed functionality works under Windows?

Files in this package

  This file.
  Change log.
  Pending improvements.
  Makefile (see "Installation" above).
  tp_smapi driver module (main code).
  thinkpad_ec driver module (coordinates hardware access between tp_smapi and
  Modified version of hdaps.c driver from mainline kernel, patched to use
  thinkpad_ec and several other improvements.
diff/*  (excluding above)
  Used by "make patch" to create a clean stand-alone patch.
  Contains a symlink to make gcc happy in kernel builds.

More about SMAPI

For hints about what may be possible via the SMAPI BIOS and how, see:

* IBM Technical Reference Manual for the ThinkPad 770
* Exported symbols in PWRMGRIF.DLL or TPPWRW32.DLL (e.g., use "objdump -x").
* drivers/char/mwave/smapi.c in the Linux kernel tree.*
* The "thinkpad" SMAPI module (
* The SMAPI_* constants in tp_smapi.c.

Note that in the above Technical Reference and in the "thinkpad" module,
SMAPI is invoked through a function call to some physical address. However,
the interface used by tp_smapi and the above mwave drive, and apparently
required by newer ThinkPad, is different: you set the parameters up in the
CPU's registers and write to ports 0xB2 (the APM control port) and 0x4F; this
triggers an SMI (System Management Interrupt), causing the CPU to enter
SMM (System Management Mode) and run the BIOS firmware; the results are
returned in the CPU's registers. It is not clear what is the relation between
the two variants of SMAPI, though the assignment of error codes seems to be

In addition, the embedded controller on ThinkPad laptops has a non-standard
interface at IO ports 0x1600-0x161F (mapped to LCP channel 3 of the H8S chip).
The interface provides various system management services (currently known:
battery information and accelerometer readouts). For more information see the
thinkpad_ec module and the H8S hardware documentation:
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