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

Basic procfs APIs

Here, we do not intend to delve into the gory details of the procfs API set; rather, we shall cover just enough to have you be able to understand and use them. For deeper detail, do refer to the ultimate resource: the kernel code base. The routines we will cover here have been exported, thus making them available to driver authors like you. Also, as we mentioned earlier, all the procfs file objects are really pseudo objects, in the sense that they exist only in RAM.

Here, we are assuming you understand how to design and implement a simple LKM; you'll find more details in the companion guide to this book, Linux Kernel Programming, in the fourth and fifth chapters. 

Let's begin by exploring a few simple procfs APIs that allow you to perform a few key tasks creating a directory under the proc filesystem, creating (pseudo) files under there, and deleting them, respectively. For all of these tasks, ensure you include the relevant header file;...