From: "H. Peter Anvin" <hpa@zytor.com>
Date: Sun, 04 Aug 2013 10:33:46 -0700

Anyone who can dig backwards and summarize?  In other words:

Where in the current code do we stuff a physical address in a pointer,
or a virtual address into a non-pointer?

The VGA register accessors try to accomodate iomem and ioport
accesses.

If they are given a non-NULL iomem pointer 'regbase' they use
iomem accesses, otherwise they do direct ISA port poking.

And yes the drivers in question are making some brash assumptions.
I suspect they should be using ioremap() or similar.