Book Image

Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization

By : Kaiwan N Billimoria
Book Image

Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization

By: Kaiwan N Billimoria

Overview of this book

Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization is an ideal companion guide to the Linux Kernel Programming book. This book provides a comprehensive introduction for those new to Linux device driver development and will have you up and running with writing misc class character device driver code (on the 5.4 LTS Linux kernel) in next to no time. You'll begin by learning how to write a simple and complete misc class character driver before interfacing your driver with user-mode processes via procfs, sysfs, debugfs, netlink sockets, and ioctl. You'll then find out how to work with hardware I/O memory. The book covers working with hardware interrupts in depth and helps you understand interrupt request (IRQ) allocation, threaded IRQ handlers, tasklets, and softirqs. You'll also explore the practical usage of useful kernel mechanisms, setting up delays, timers, kernel threads, and workqueues. Finally, you'll discover how to deal with the complexity of kernel synchronization with locking technologies (mutexes, spinlocks, and atomic/refcount operators), including more advanced topics such as cache effects, a primer on lock-free techniques, deadlock avoidance (with lockdep), and kernel lock debugging techniques. By the end of this Linux kernel book, you'll have learned the fundamentals of writing Linux character device driver code for real-world projects and products.
Table of Contents (11 chapters)
1
Section 1: Character Device Driver Basics
3
User-Kernel Communication Pathways
5
Handling Hardware Interrupts
6
Working with Kernel Timers, Threads, and Workqueues
7
Section 2: Delving Deeper

Summary

This concludes this chapter on writing a simple misc class character device driver on the Linux OS; so, awesome, you now know the basics of writing a device driver on Linux!

The chapter began with an introduction to device basics, and importantly, the very brief essentials of the modern LDM. You then learned how to write a simple first character device driver, registering with the kernel's misc framework. Along the way, you also understood the connection between the process, the driver, and the kernel VFS. Copying data between user and kernel address spaces is essential; we saw how to do so. A more comprehensive demo misc driver (our 'secret' driver) showed you how to perform I/O – reads and writes – ferrying data between user and kernel space. A key part of this chapter is the last section, where you learned (well, made a start at least) about security and the driver; a "hack" even demonstrated a privesc attack!

As mentioned before, there's much more to this vast topic of writing drivers on Linux; indeed, whole books are devoted to it! Do check out the Further reading section for this chapter to find relevant books and online references.

In the following chapter you will learn a key task for a driver author - how exactly can you efficiently interface your device driver with user space processes; several useful approaches are covered in detail and contrasted. Do ensure you're clear on this chapter's material, work on the exercises given, review the Further reading resources and then dive into the next one.