This book has been written with a view to helping you learn the fundamentals of Linux character device driver development in a practical, hands-on fashion, along with the necessary theoretical background to give you a well-rounded view of this vast and interesting topic area. To do the topics justice, that book's scope is deliberately kept limited to (mostly) learning how to write misc class character device drivers on the Linux OS. This way, you will be able to deeply imbibe the fundamental and necessary driver author skills to then be able to tackle different kinds of Linux driver projects with relative ease.

The focus is on hands-on driver development via the powerful Loadable Kernel Module (LKM) framework; the majority of kernel driver development is done in this manner. The focus is kept on working hands-on with driver code, understanding at a sufficiently deep level the internals wherever required, and keeping security in mind.

A recommendation we can't make strongly enough: to really learn and understand the details well, it's really best that you first read and understand this book's companion, Linux Kernel Programming. It covers various key areas – building the kernel from source, writing kernel modules via the LKM framework, kernel internals including kernel architecture, the memory system, memory alloc/dealloc APIs, CPU scheduling, and more. The combination of the two books will give you a sure and deep edge.

This book wastes no time – the first chapter has you learning the details of the Linux driver framework and how to write a simple yet complete misc class character device driver. Next, you learn how to do something very necessary: efficiently interfacing your driver with user space processes using various technologies (some of which help as debug/diagnostic aids as well!). Understanding, and working with, hardware (peripheral chip) I/O memory is then covered. Detailed coverage of handling hardware interrupts follows. This includes learning and using several modern driver techniques – using threaded IRQs, leveraging resource-managed APIs for drivers, I/O resource allocation, and so on. It covers what top/bottom halves are, working with tasklets and softirqs, and measuring interrupt latencies. Kernel mechanisms you will typically work with – using kernel timers, setting up delays, creating and managing kernel threads and workqueues – are covered next.

The remaining two chapters of this book delve into a relatively complex yet critical-to-understand topic for the modern pro-level driver or kernel developer: understanding and working with kernel synchronization.

The book uses the latest, at the time of writing, 5.4 Long Term Support (LTS) Linux kernel. It's a kernel that will be maintained (both bug and security fixes) from November 2019 right through December 2025! This is a key point, ensuring that this book's content remains current and valid for years to come!

We very much believe in a hands-on empirical approach: over 20 kernel modules (besides a few user apps and shell scripts) on this book's GitHub repository make the learning come alive, making it fun, interesting, and useful.

We really hope you learn from and enjoy this book. Happy reading!