You probably want to read all you can on resource managers, as this is a natural form to put a hardware driver in.
Rob Krten’s book “Getting started with QNX Neutrino 2” is a good resource if the docs aren’t enough, although it may be hard to get ahold of. I’ve heard QSSL has taken it over so you can check with them. There are a few topics for dealing with hardware that I’ll list. Ask again about any specifics:
- port I/O (You need to use ThreadCtl() and be super user
- DMA (Shared) memory
- PCI inquiry
There are other idiosyncratic areas, such as PCMCIA/CARDBUS, USB, and Network drivers for which there are development kits available.