aps
—
ThinkPad Active Protection System accelerometer
The aps
driver provides support for several sensors
found in some ThinkPad laptops.
The sensors currently exposed via the
envsys(4) interface are:
The aps
driver first appeared in
OpenBSD 3.8 and was then ported to
NetBSD 5.0.
Few issues can be mentioned.
- The
aps
driver does not maintain state and
subsequently does not take evasive action when it thinks the hard drive is
in danger. Possible actions would include spinning down the hard drive in
case excessive tremor is detected by the sensors.
- The Y axis on X40 and possibly other models seems to be inverted. It is
unknown how to distinguish between different versions of the accelerometer
to compensate for this in the driver at this time.
- The sensor values are refreshed every 0.5 seconds. Because no protection
measures are taken, this is unnecessary and may have a negative effect on
battery life.
- As IBM provides no documentation, it is not known what all the available
sensors are used for.