Book Image

Linux Device Driver Development - Second Edition

By : John Madieu
Book Image

Linux Device Driver Development - Second Edition

By: John Madieu

Overview of this book

Linux is by far the most-used kernel on embedded systems. Thanks to its subsystems, the Linux kernel supports almost all of the application fields in the industrial world. This updated second edition of Linux Device Driver Development is a comprehensive introduction to the Linux kernel world and the different subsystems that it is made of, and will be useful for embedded developers from any discipline. You'll learn how to configure, tailor, and build the Linux kernel. Filled with real-world examples, the book covers each of the most-used subsystems in the embedded domains such as GPIO, direct memory access, interrupt management, and I2C/SPI device drivers. This book will show you how Linux abstracts each device from a hardware point of view and how a device is bound to its driver(s). You’ll also see how interrupts are propagated in the system as the book covers the interrupt processing mechanisms in-depth and describes every kernel structure and API involved. This new edition also addresses how not to write device drivers using user space libraries for GPIO clients, I2C, and SPI drivers. By the end of this Linux book, you’ll be able to write device drivers for most of the embedded devices out there.
Table of Contents (23 chapters)
1
Section 1 -Linux Kernel Development Basics
6
Section 2 - Linux Kernel Platform Abstraction and Device Drivers
12
Section 3 - Making the Most out of Your Hardware
18
Section 4 - Misc Kernel Subsystems for the Embedded World

Learning how not to write GPIO client drivers

There are situations where writing user space code would achieve the same goals as writing kernel drivers. Moreover, the GPIO framework is one of the most used frameworks in the user space. It then goes without saying that there are several possibilities to deal with it in the user space, some of which we will introduce in this chapter.

Goodbye to the legacy GPIO sysfs interface

Sysfs has ruled GPIO management from the user space for quite a long time now. Though it is scheduled for removal, the sysfs GPIO interface still has a few days ahead of it. CONFIG_GPIO_SYSFS can still enable it, but its use is discouraged, and it will be removed from mainline Linux. This interface allows managing and controlling GPIOs through a set of files. It is located at /sys/class/gpio/, and the following are the common directory paths and attributes that are involved:

  • /sys/class/gpio/: This is where it all starts. There are two special files...