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

Having your work task execute schedule_work()

Calling INIT_WORK() registers the specified work structure and function with the in-house default kernel-global workqueue. But it doesn't execute it yet! You have to tell it when to execute your "work" by calling the schedule_work() API at the appropriate moment:

bool schedule_work(struct work_struct *work);

Clearly, the parameter to schedule_work() is the pointer to the work_struct structure (which you initialized earlier via the INIT_WORK() macro). It returns a Boolean (quoting directly from the source): %false if @work was already on the kernel-global workqueue and %true otherwise True. In effect, schedule_work() checks if the function that was specified (via the work structure) is already on the kernel-global workqueue; if not, it enqueues it there; if it already was there, it leaves it alone in the same position (it doesn't add one more instance). It then marks the...