This article is about configuring the timeout which is responsible for turning off the backlight of a Latitude’s keyboard after a keyboard, touchpad or track stick action. By default is it configured at 10 seconds which I wanted to change. As I had a hard time finding information about the issue, I hope this article can help others going through less trouble. If you are using Linux and are not interested in the history, you can skip right to the solution.
A bit of history
I bought a Dell Latitude E5450 about a year ago. On paper it combined everything I wanted, a matte screen (I want to see what’s on my screen, not my face), backlit US keyboard (better for programming) a pointing stick (my fingers seem to be incompatible with touchpads and it’s great for scrolling) and an OK price. The only alternatives would have been HP, but they don’t have a middle button for their pointstick which is vital for scrolling, and Lenovo, but at the time they only had Thinkpads without physical trackpoint buttons(horrible, but I guess a lot of people complained, because now they all have physical buttons again - too late for me).
I write “on paper”, because it has two big problems. I still don’t have a solution for the first one: there is a ~500ms delay between hitting a key and using the track stick or its button. Sounds short, but is very noticeable. At first I thought it’s due to the missing driver support of the current Xubuntu back then as I also had problems with middle button detection and missing palm check configuration. But as I still had the delay, but not the other problems after an update to the latest Xubuntu, I contacted the support. After a lot of back and forth and even swapping the keyboard a few times (the support first thought it’s a hardware issue and then Dell had a hard time getting me a keyboard without broken keys or broken backlight so I even got a new unit…) it turns out it’s working according to spec. Such a delay might make sense for touchpads, but even there it’s configurable (palm check). It doesn’t make sense for pointing sticks. But all the arguing in the world did not help, it’s working according to spec and as such not a problem for Dell.
Weird configuration values don’t have to be a problem, if they can be changed easily. But where the track stick delay is not configurable at all, the keyboard backlight timeout is just very hard to change. On my first unit, I installed Linux right away so as I encountered this timeout and could not change it easily, I thought it’s my fault for using Linux. I found the below solution but it took a while to get it to work. Like everything that doesn’t work out-of-the-box does under Linux. On my second unit, a year later and without documentation on what I did, I figured I just keep Windows, install Linux with dual boot and whenever I have a problem I can just use the drivers from Dell under Windows. Well, no. Google revealed many hits with people having the same problem, but all the Windows solutions used drivers/software that doesn’t exist any more. So currently there doesn’t seem to be an easy way to change the timeout under Windows. I guess the below solution could still be used from a Linux live CD, but how many Windows users know how to do that?
One of my Google searches pointed me to libsmbios but it seemed helplessly outdated. After more searching I came across the libsmbios git repository which finally allowed me to change the timeout. However, it works only under Linux (tested under Xubuntu 15.10).
So lets get started, first you need to get the sources and compile them.
Now you can change into the installation folder and set the timeout:
You are done! The value is stored in the BIOS, so it will outlive a new OS installation and even a new keyboard.
After 5 years, there seems to be a new release of libsmbios from 3 days ago with an addition regarding the keyboard backlight, but it does not seem to affect this solution. Maybe there will be the possibility to configure the timeout in the BIOS at some point, but currently it isn’t - at least not for the E5450.