Comment 17 for bug 194489

Using powertop to monitor cpu wakeups on a laptop on battery (my case: thinkpad t400), the number of wakeups rises for the "PS/2 keyboard/mouse/touchpad" from less than five to around 400 hundred or more (resulting in a rise in power consumption of 2-3 Watts in most cases -- quite significant on a laptop) when the touchpad is used.

How to reproduce: Start powertop as root when the machine is idle and wait for it to stablize it's measurements. Then move the pointer around a lot, and wait for powertop to refresh its readings. The same effect is not seen while typing.

The same issue has also been reported elsewhere:

Ubuntu bug report:
https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-input-synaptics/+bug/194489

Arch linux forum thread:
http://bbs.archlinux.org/viewtopic.php?pid=486690

As the same appears on different distributions and kernel versions, it is likely to be caused by the driver, although I can't be sure.

My system specs:
Lenovo Thinkpad T400
Synaptics touchpad (part of an UltraNav)
Arch Linux x86_64
version 0.99.3 of xf86-input-synaptics