[srn]

This may not be likely, but - you don't specify a level for your printk statement. It could be your message is just not getting printed to console. Check out info for "/proc/sys/kernel/printk" as well as information about syslogd and klogd as the message may be logged to somewhere else.

I also would like to mention that in general memory barriers can be useful for working with i/o irrespective of your particular situation.

[srn]

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.

[srn]

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.