Simple device driver

Hi folks,

I need to write a simple device driver to write a value to an I/O port to
implement a watchdog.
I’ve read the excellent section in Rob Krten’s book about how to write a
resource manager but this focuses solely on the client interfacing and has
no information regarding how to write to the port.
At the moment I can implement a simple driver which receives write
instructions from a client process, etc. but I don’t know what to do to
actually write to the hardware port. I expect that this is pretty
straightforward (if you know how)?

Any advice would be appreciated.

Cheers,

Liam Power.