Beginner question about GPIO and mirage build process

[Michael Chiu <chiu@xxxxxxxxxxxxxx>]

Hi Everyone,

I was hoping to get some help / advice on two related issues.

1. I'm new to both OCaml and MirageOS and am trying to figure out how to 
access GPIO when targeting a unix backend. I've looked at all the 
tutorials and have a basic understanding of how mirage works, but 
couldn't find more in depth documentation on what's happening behind the 
scenes, or what the available configuration options are for. Does the 
unix backend have support for GPIO? Is there some documentation that I 
haven't found?  I'd appreciate some advice to better understanding mirageOS.
2. I'm not too familiar with the build system in both ocaml and 
mirageos, but I do know how to make a simple module package using dune. 
I'm trying to get a custom module working in mirage but it's unclear to 
tell the mirage toolchain about my custom module.
Any suggestions are appreciated, thanks in advance.

--
Michael.