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

Working with the threaded interrupts model

As seen in the companion guide Linux Kernel Programming - Chapter 11The CPU Scheduler – Part 2, in the Converting mainline Linux into an RTOS section, we covered the real-time patch for Linux (RTL), which allows you to patch, configure, build, and run Linux as an RTOS! If you're hazy on this, please refer back to this. We won't repeat the same information here.

The Real-Time Linux (RTLproject's work has been steadily back-ported into the mainline Linux kernel. One of the key changes wrought by RTL was merging the threaded interrupts feature into the mainline kernel. This occurred in kernel version 2.6.30 (June 2009). This technology does something that, at first glance, seems very weird: it "converts" the hardware interrupt handler into, essentially, a kernel thread.

As you will learn in the next chapter, a kernel thread is really very similar...