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

Creating a simple platform device

Clearly, in order to create a (pseudo) file under sysfs, we somehow require, as the first parameter to device_create_file(), a pointer to a struct device. However, for our demo sysfs driver here and now, we don't actually have any real device, and therefore no struct device, to work on!

So, can't we create an artificial or pseudo device and simply use it? Yes, but how, and more crucially, why exactly should we have to do this? It's critical to understand that the modern Linux Device Model (LDM) is built on three key components: an underlying bus must exist that devices live on, and devices are "bound to" and driven by device drivers. (We already mentioned this in Chapter 1Writing a Simple misc Character Device Driver, in the A quick note on the Linux Device Model section).

All of these must be registered to the driver core. Now, don't worry about the buses and the bus drivers that drive them; they...