Thanks a lot for your suggestions!

I've removed the file open check for readability, there's no problem with open() nor ioctl() on this level; the latter returns "0 but true".

Your sanity check returns a whopping:

PCIMAX_IOC_SET_REGISTER is -2147471359
[download]

Packing the value (or not) does not help. The pass by reference I borrowed from some sample code. Yet never mind how it is passed, I don't get that bleedin' value over to the corresponding kernel module function.

Inline::C might work, but there has to be another way, after all, it's a simple IO call :-)

Your help is very much apprechiated!
Sven