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

Approaches to communicating/interfacing a kernel driver with a user space C app

As we mentioned in the introduction, in this chapter, we wish to learn how to efficiently transfer information between a kernel-space component (often, this is a device driver, but it could be anything, really), and a user space process or thread. To begin, let's simply enumerate various techniques available to the kernel or driver author to communicate or interface with a user space C application. Well, the user space component could be a C app, a shell script (both of which we typically show in this book), or even other apps such as C++/Java apps, Python/Perl scripts, and more.

As we saw in the companion guide, Linux Kernel Programming, in Chapter 4, Writing Your First Kernel Module LKMs Part 1, in the Library and System Call APIs subsection, the essential interface between user space applications and the kernel that includes the device drivers are the system call APIs. Now,...