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

Understanding and using memory-mapped I/O

In the MMIO approach, the CPU understands that a certain region (or several) of its address space is reserved for I/O peripheral memory. You can actually look up the region(s) by referring to the physical memory map of a given processor's (or SoC's) datasheet.

To help make this clearer, let's take a look at a real example: the Raspberry Pi. As you'll be aware, this popular board uses a Broadcom BCM2835 (or later) SoC. The BCM2835 ARM Peripherals document at, on page 90, provides a screenshot of a small portion of its physical memory map. The mapping of the SoC's General Purpose Input/Output (GPIO) registers shows a portion of the hardware I/O memory in the processor's address space:

Figure 3.1 – Physical memory map on the BCM2835 showing the GPIO register bank
Well, the reality...