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

Hardware interrupts and how the kernel handles them

Many, if not most, peripheral controllers use a hardware interrupt to inform the OS or device driver that some (usually urgent) action is required. Typical examples include network adapters (NICs), block devices (disks), USB devices, AV devices, human interface devices (HIDs) such as keyboards, mice, touchscreens, and video screens, clocks/timer chips, DMA controllers, and so on. The primary idea behind hardware interrupts is efficiency. Instead of continually polling the chip (on a battery-backed device, this can result in rapidly draining the battery!), the interrupt is a means to have the low-level software run only as and when required.

Here's a quick hardware-level overview (without getting into too much detail): modern system motherboards will have an interrupt controller chip of some sort, which is often called the [IO][A]PIC, short for IO-[Advanced] Programmable Interrupt Controller, on x86 (the kernel documents for...