A solution to fix the hardware keyboard lights for Sony Xperia X10 Mini Pro has been exposed to the public. It happens after one of xda member forum share the app to turn on LED lights when you slide out the keyboard than LED lights off when you slide in. This condition will definitely improve your battery life.
The app is just an initial release version and issues may be still unreported but it is very useful especially for anyone who waits long time to found the correct tool or Android app because the LEDs that acts as a backlight for the keyboard. Sometimes they don’t light up, and sometimes they stay lit up after the device is closed, leading both to poor battery life and an oddly glowing device.

However many a lot of custom ROMs for X10 Mini Pro but many of them did not address to resolve the problem to turn on the hardware LED’s. By this article posted in Xperia Android phone site, hopefully you will find the correct android app for your Xperia X10 Mini Pro. You can find the app through original Android development software download link.
Hopefully in future the keyboard fix apk file update to new version by adding some new features and improve the speed of the app.
If you would like to give a try, let’s download the keyboard fix apk from download link than install manually to your phone. If you would like to share your findings, share or feedback to the developer, please don’t hesitate to join discussion on android development original page. It is very important to enhance the app to next level with some new features or any bug found to fix the hardware keyboard lights for X10 Mini Pro.