[ltp] Fingerprint reader occasionally gets hot (T61)

[Tino Keitel]

On Fri, Aug 01, 2008 at 11:58:52 +0100, Daniel Castro wrote:
> Hello,
>
> I have noticed that the fingerprint reader gets hot some times. My HDD  
> is under the reader and I'm sure it is not the HDD what is making it  
> warm-up.
> Does anyone else has experienced this? How to know why this is  
> happening? What  to do to cool it down?
> As I said this happens occasionally, and the reader works flawlessly for  
> me, I use it a lot. It's just a bit uncomfortable to have that hot thing  
> in my palm.

I gues that the fingerprint reader USB device hasn't autosuspend
enabled, so it is "on" all the time.

Try this:

$ for i in `find /sys/devices/*/*/usb* -name level` ; do echo -n "$i: " ; cat $i ; done

If there is one ore more device in state "on", use lsusb to get the
vendor/device ID of the fingerprint reader, and check if it matches one
of the devices in state "on". Example:

output of the above for loop:

/sys/devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.1/power/level: on

check vendor/device ID:

$ cat /sys/devices/pci0000\:00/0000\:00\:1d.7/usb1/1-1/1-1.1/idVendor 
04d9
$ cat /sys/devices/pci0000\:00/0000\:00\:1d.7/usb1/1-1/1-1.1/idProduct 
1400

If you spotted the sysfs device that matches the fingerprint reader, to
this:

echo "auto" > /sys/<path-to-device>/power/level

After this, the fingerprint reader should be in state "autosuspend" and
don't get got anymore.

For a short ckeck, you can also use powertop -d and watch the USB
status output. This works with powertop 1.10 and above.

I just disabled the fingerprint reader in the BIOS as it is insecure
anyway.

Regards,
Tino