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

The simpler atomic_t and refcount_t interfaces

Regarding the atomic_t interfaces, we should mention that all the following atomic_t constructs are for 32-bit integers only; of course, with 64-bit integers now being commonplace, 64-bit atomic integer operators are available as well. Typically, they are semantically identical to their 32-bit counterparts with the difference being in the name (atomic_foo() becomes atomic64_foo()). So the primary data type for 64-bit atomic integers is called atomic64_t (AKA atomic_long_t). The refcount_t interfaces, on the other hand, cater to both 32 and 64-bit integers.

The following table shows how to declare and initialize an atomic_t and refcount_t variable, side by side so that you can compare and contrast them:

(Older) atomic_t (32-bit only) (Newer) refcount_t (both 32- and 64-bit)

Header file to include

<linux/atomic.h>

<linux/refcount.h>

Declare and initialize a variable static atomic_t gb...