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


In this chapter, you learned why we can't just work directly with peripheral I/O memory. Next, we covered how, within the Linux device driver framework, to access and perform I/O (reads and writes) on hardware (or peripheral) I/O memory. You learned that there are two broad ways to do this: via MMIO (the common approach) and P(M)IO.

We learned that systems such as the x86 often employ both approaches as that's how the peripherals are designed. MMIO and/or PMIO access is a key task for any driver  after all, this is how we talk to and control hardware! Not only that, but many of the underlying bus drivers (for various buses on Linux, such as I2C, USB, SPI, PCI, and more) internally use MMIO/PMIO for performing peripheral I/O. So, good job on completing this chapter!

In the next chapter, we'll look at another critical hardware-related area of importance: understanding, dealing with, and working with hardware interrupts.