I want to understand the "coef" member of this struct.
Is this used to set axis values? If yes, then are the axis
values to be set as follows?

1. Center Min
   
2. Center Max
   
3. Range Min
   
4. Range Max
   

If I set the values as shown in the screenshot below to struct directly in the program, will that make sense?

I'm sorry, but this is so not the forum where to ask about Linux joystick driver implementations. I suggest you consult "jscal.c" to understand how the calibration is done. I believe that "coef" holds correction coefficients for devices that don't report the axes range within -16384 to 16384.

But MadCat, weren't you who had written a patch for the joystick driver? I saw your post in this forum, that's why thought this could be the place to ask.

I did write the major part of the Logitech wheels patch, however, I didn't have to work directly with the joystick driver, only with the USB/HID. The discussion regarding the development having taken place here was a bit of a coincidence as Live For Speed is a windows-targeted game and you're not likely to meet someone well versed in Linux stuff on the forums.
I guessed the meaning if the variable in question by reading the jscal source file (that's what the official documentation of the joystick drivers suggests).

There should be my email mentioned in one of the patches that've been merged into 3.2 mainline. If you have any questions I could answer, feel free to contact me that way...