Book Image

Linux Device Drivers Development

By : John Madieu
Book Image

Linux Device Drivers Development

By: John Madieu

Overview of this book

Linux kernel is a complex, portable, modular and widely used piece of software, running on around 80% of servers and embedded systems in more than half of devices throughout the World. Device drivers play a critical role in how well a Linux system performs. As Linux has turned out to be one of the most popular operating systems used, the interest in developing proprietary device drivers is also increasing steadily. This book will initially help you understand the basics of drivers as well as prepare for the long journey through the Linux Kernel. This book then covers drivers development based on various Linux subsystems such as memory management, PWM, RTC, IIO, IRQ management, and so on. The book also offers a practical approach on direct memory access and network device drivers. By the end of this book, you will be comfortable with the concept of device driver development and will be in a position to write any device driver from scratch using the latest kernel version (v4.13 at the time of writing this book).
Table of Contents (23 chapters)
Free Chapter
1
Introduction to Kernel Development

Advanced peripheral IRQs management

In Chapter 3, Kernel Facilities and Helper Functions, we introduced peripheral IRQs, using request_irq() and request_threaded_irq(). With request_irq(), one registers a handler (top half) that will be executed in atomic context, from which one can schedule a bottom half using one of a differing mechanism discussed in that same chapter. On the other hand, with request_thread_irq(), one can provide top and bottom halves to the function, so that the former will be run as a hardirq handler, which may decide to raise the second and threaded handler, which will be run in a kernel thread.

The problem with those approaches is that sometimes, drivers requesting an IRQ do not know about the nature of the interrupt that provides this IRQ line, especially when the interrupt controller is a discrete chip (typically a GPIO expander connected over SPI or I2C...