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)
Section 1: Character Device Driver Basics
User-Kernel Communication Pathways
Handling Hardware Interrupts
Working with Kernel Timers, Threads, and Workqueues
Section 2: Delving Deeper


Well done! We covered a lot of ground in this chapter. First, you learned how to create delays in kernel space, both the atomic and the blocking types (via the *delay() and *sleep() routines, respectively). Next, you learned how to set up and use kernel timers within your LKM (or driver) a very common and required task. Directly creating and working with kernel threads can be a heady (and even difficult) experience, which is why you learned the basics of doing so. After that, you looked at the kernel workqueue subsystem, which solves complexity (and concurrency) issues. You learned what it is and how to practically make use of the kernel-global (default) workqueue to make your work task(s) execute when required.

The series of three sed (simple encrypt decrypt) demo drivers we designed and implemented showed you a bit of a more sophisticated use case for these interesting technologies: sed1 with the timeout implementation, sed2 adding to the kernel thread to perform...