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

Code view 4 the STM32 F7 microcontroller's threaded interrupt handler

The STM32 F7 is part of a series of microcontrollers that have been manufactured by STMicroelectronics, based on the ARM-Cortex M7F core:

Figure 4.3 – The STM32F103 microcontroller pinout with some I2C pins highlighted (see the lower left)
Image Credit: The preceding image, which has been slightly added to by myself, has been taken from Image by Rasmus Friis Kjekisen. This image falls under Creative Commons CC BY-SA 1.0 (

The Linux kernel supports the STM32 F7 via various drivers and DTS files. Here, we'll take a look at a tiny bit of the code for the I2C bus driver (drivers/i2c/busses/i2c-stm32f7.c) for this microcontroller. It allocates two hardware interrupts:

  • The event IRQ line, via the devm_request_threaded_irq...