The Curious Case of HID Malfunction

2010/08/21 § Leave a comment

A quick tidbit for any interested hardware wizards out there (I know no one is likely to care, this is really more of an excuse for why the next Python’s Innards post is progressing slowly). As some of you know, I’m currently on a long trip with my wife (a trip which is already nearing its end…). This means I’m rather poor in hardware, and that sometimes the environment is harsh – hot, cold, humid, occasionally vibrating (flights, boats), rich with small particles (sand, dust), etc. As I expected for a long time, the elements finally had their toll on my small but until now trusty Asus EeePC 1005HA. The thing is, the toll was taken in a rather odd way.

For about three days now the builtin trackpad stopped working – most of the time. Usually I get no cursor movement nor clicks, and there are no particular messages in dmesg//var/log/messages. On rare occasions the trackpad resumes working for a bit, I wasn’t able to find a pattern in what makes it work for these short periods of time (heating, cooling, sleeping, booting… nothing seems to make the short ‘work-periods’ predictable). On one occasion the trackpad worked but behaved erratically (jumping around, random clicks, etc), on others it works fine, but for a few seconds and up to a few minutes. I’m running Ubuntu 10.04, kernel 2.6.32-24, keeping it reasonably apt-get updated. I didn’t change anything significant in the software configuration of the computer before this happened, and booting a vanilla 10.04 from a USB stick I have around doesn’t help, so I’m pretty sure it’s not a vanilla software issue (despite the oddity listed below).

This is patently unpleasent but not entirely odd, and I would chalk it down to some undefined hardware damage and let it be. I could buy an external mouse for the remaining few weeks of the trip and otherwise ignore the issue, lest the builtin keyboard started showing similar behaviour. It works far more often than the mouse, but has spells of brokeness. An external USB keyboard works fine when plugged in. I don’t even know if my internal keyboard interfaces via some kind of internal USB controller or not; seems not, as even when it’s working it’s not listed in lsusb -v. /proc/bus/input/devices lists an “AT Translated Set 2 keyboard”, but I have no idea if this is really my keyboard or not. Anyway, the really weird thing is that the keyboard’s broken behaviour has a few extra odd quirks:

  • It works perfectly prior to loading the kernel: in the BIOS configuration screen, or GRUB’s menu, or the USB stick’s boot menu. It seems that as soon as the kernel is loaded, no more keyboard (X11 or console).
  • The “special” EeePC keys, like toggling wifi or changing screen brightness, work perfectly. They aren’t special keys, but rather a key combination, and the keys used in the combination don’t reach the OS discreetly.
  • When I open the laptop’s lid in sleep, I need to hit a key to bring it out of sleep. Any key works well enough for the computer to wakeup, and the very same key (or any other key) will promptly stop working when the OS is awake enough to ask for a password.

So what gives? My keyboard isn’t broken, but some kind of interface between the keyboard and the system which is circumvented by the BIOS but is used by the kernel is broken? Huh, WTF?

The bit of Googling I did yielded nothing, Internet here isn’t really scarce but it isn’t abundant and sure is not fast or pleasent (I’m on a beach in Thailand at the moment). I’m left with a big WTF and apt-get install keynav. Any tips will be greatly appreciated (and speed up the next post in the Python’s Innards series, too!).

Update: I’ve decided to disassemble and reassemble the keyboard, following these instructions, using a swiss-army knife, my wife’s fingernail file and a camping torch. Following the work both keyboard and touchpad are working for about 10 minutes now, one of the longer durations in the past few days. I can only hope I fixed the problem. Either way, I’m curious why the keyboard consistently didn’t work with a loaded kernel yet seemed to work fine using the BIOS (in the BIOS’ setup, GRUB’s boot menu, etc). Any explanations?


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