Dan,

I was thinking the same thing, and I did change the driver so that it does its I/O through the "parport" driver stack rather than directly accessing the x86 legacy register addresses. However, I was disappointed to discover most USB parallel port adapters don't plug into the parport stack. Instead they look like a USB printer to the OS.

I went another way and designed a parallel port "HAT" for the raspberry pi. I have a prototype that works with PHD + indi + sbigudrv reliably as long as the cable is really short. I'm working on a second revision of the hardware that hopefully will have better electrical characteristics.

This project is over here (with driver and board layout):

github.com/garlick/pi-parport

Jim

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