Writing a kernel device driver

Eventually, when you have exhausted all the previous user space options, you will find yourself having to write a device driver to access a piece of hardware attached to your device. Character drivers are the most flexible and should cover 90% of all your needs; network drivers apply if you are working with a network interface and block drivers are for mass storage. The task of writing a kernel driver is complex and beyond the scope of this book. There are some references at the end that will help you on your way. In this section, I want to outline the options available for interacting with a driver – a topic not normally covered – and show you the bare bones of a character device driver.

Designing a character driver interface

The main character driver interface is based on a stream of bytes, as you would have with a serial port. However, many devices don't fit this description: a controller for a robot arm needs functions to...