"use register arguments" option enabled.

[Mike Honeyfield]

I am just wondering the reasoning behind having the experimental
option "Use register arguments" on in the kernel config.

It has caused some issues for me, have since fixed it, but was
wondering why an experimental feature that could/can break the ABI for
3rd party binary only modules would be enabled?

I have noted this on FC2/3, not yet looked at FC4test and also RHEL4. 

Thanks in advance. 

Mike