Can i export this variable now?

I do not think so, we do not export random variables.

What is your suggestion?

But I already did provide you suggestions - kill this global variable
completely. I provided the reasons:

1. It is error prone to hide functions behind something which looks like
a constant.
2. Multiple controllers with different base addresses wouldn't work -
your driver has to be able to at least theoretically handle multiple
controllers with different bases.

-- 
Best Regards,
Artem Bityutskiy (???????? ?????)