More explicit handling of error conditions is also good FWIW - don't see you doing it here. The kernel is not forgiving of using resources your don't have or failing to free resources acquired.
Also from what I know, which is not much, you should be requesting the ports via request_region. If that fails you should probably not be writing to the ports and should also mean you're sharing the port with another module.
kernel newbies is theoretically a good place to go with these kinds of questions too.
kernel newbies is theoretically a good place to go with these kinds of questions too.