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)
1
Section 1: Character Device Driver Basics
3
User-Kernel Communication Pathways
5
Handling Hardware Interrupts
6
Working with Kernel Timers, Threads, and Workqueues
7
Section 2: Delving Deeper

Let's try it – how long do delays and sleeps really take?

By now, you know how to use the *delay() and *sleep() APIs to construct delays and sleeps (non-blocking and blocking, respectively). Hang on, though  we haven't really tried it out in a kernel module. Not only that, are the delays and sleeps as accurate as we have been led to believe? Let's, as usual, be empirical (this is important!) and not make any assumptions. Let's actually try it out for ourselves!

The demo kernel module we'll be looking at in this subsection performs two kinds of delays, in order:

  • First, it employs the *delay() routines (which you learned about in the Understanding how to use the *delay() atomic APIs section) to implement atomic non-blocking delays of 10 ns, 10 us, and 10 ms.
  • Next, it employs the *sleep() routines (which you learned about in the Understanding how to use the *sleep() blocking APIs section) to implement...