How to calibrate /dev/input/eventX joystick?

Hello,

I have a software, which uses my joystick via /dev/input/eventX and not 
/dev/input/jsX.

Unfortunately the "dead zone" is too big. I need some way to reduce this. How 
can this be done? I've searched through the kernel source, but I didn't find the 
source files, responsible for creating the event devices for joysticks. 
Calibrating the jsX device doesn't seem to change anything with the eventX device.

Thanks in advance

Yours

Manuel