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

Using kernel timers

In order to use a kernel timer, you must follow a few steps. Here's what to do in a nutshell (we'll discuss this in more detail afterward):

  1. Initialize the timer metadata structure (struct timer_list) with the timer_setup() macro. The key items that get initialized here are as follows:
    • The time to expire by (that value that jiffies should reach for the timer to expire)
    • The function to invoke when the timer expires  in effect, the timer "callback" function
  2. Write the code for your timer callback routine.
  3. When appropriate, "arm" the timer – that is, have it start  by invoking the add_timer() (or mod_timer()) function.
  4. When the timer times out (expires), the OS will automatically invoke your timer's callback function (the one you set up in step 2); remember, it will be running in the timer softirq or an atomic or interrupt context.
  5. (Optional) Timers are not cyclic, they are one-time by...