ISA device driver and IRQs

[david hodges]

I need to write a simple device driver for the ISA bus that uses one IRQ and a few reads and writes to I/O Ports 0x300 +. I don't know even where to start with FreeBSD. I've done drivers before in other OS systems and have a book for Linux but FreeBSD seems MUCH differnt. Are there any examples I can get?  I thought about modifying the serial driver but I'm not een sure if that's a good idea. Any help would be great. ThanksDave