save battery: how to disable usb fingerprint, camera?

otoomet · 01-25-2012, 10:24 AM

Gurus --

powertop reports that my laptop (thinkpad X220, kernel 3.0 64bit) drains about 500mW for both the USB fingerprint reader and the integrated webcam. I never use fingerprint (the optical parts are not even installed although the chip is seemingly sitting on the motherboard), and only seldom the webcam.

Is it possible to disable these devices by commandline (not affecting the rest of the usb)? I have seen threads, suggesting to echo "suspend" to /sys/bus/usb/devices/*/power/control, but it seems like this does not work any more with the newer kernel. Is there any better way?

edit: lsusb:

Code:

$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 003: ID 147e:2016 Upek Biometric Touchchip/Touchstrip Fingerprint Sensor
Bus 001 Device 005: ID 04f2:b217 Chicony Electronics Co., Ltd

ukiuki · 01-26-2012, 03:16 AM

You may want check the BIOS to see if there is an option, maybe backlist the module for it would stop it to load on boot.

Regards

otoomet · 01-27-2012, 03:21 AM

The BIOS does not allow to switch off a single device.

However, I am suspecting powertop has problems understanding which devices exactly are draining the battery. Yesterday, all the day it reported the USB webcam taking 6W(!) while fingerpring reader was not even mentioned. Today, the top of the list reads

Code:

  1.30 W     1911 rpm                   Device         Laptop fan
  895 mW    100.0%                      Device         USB device: Biometric Coprocessor (UPEK)
  846 mW     50.6 ms/s      82.7        Process        /usr/lib/firefox-9.0.1/firefox
  846 mW     40.0%                      Device         Display backlight
  727 mW     1500 pkts/s                Device         Network interface: eth0 (e1000e)
  615 mW     22.6 ms/s     133.2        Process        /usr/lib/nspluginwrapper/i386/linux/npviewer.bin --plugin /usr/lib/flashplugin-installer/
  505 mW     12.9 ms/s     138.0        Process        /usr/lib/firefox-9.0.1/plugin-container /var/lib/flashplugin-installer/npwrapper.libflash
  472 mW     15.3%                      Device         Display backlight
  231 mW    100.0%                      Device         Radio device: iwlagn

As you see, webcam is not there (nor anywhere down in the list). I haven't used it for 2 weeks.

Thank you anyway, ukiuki.

ukiuki · 01-28-2012, 05:49 AM

I found this and maybe it is interesting to you it does help to save battery.
http://forums.debian.net/viewtopic.php?f=16&t=29774

Regards