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

Implementing the interrupt handler routine

Often, the interrupt is the hardware peripheral's way of informing the system  the driver, really  that data is available and that it should pick it up. This is what typical drivers do: they grab the incoming data from the device buffers (or port, or whatever). Not just that, it's also possible that there are user mode processes (or threads) that want this data. Thus, they have quite possibly opened the device file and have issued the read(2) (or equivalent) system call. This has them currently blocking (sleeping) upon this very event; that is, data arriving from the device.

On detecting that data currently isn't available, the driver's read method typically puts the process context to sleep using one of the wait_event*() APIs.

So, once your driver's interrupt handler has fetched the data into some kernel buffer, it typically awakens the sleeping readers. They now run through the driver...