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

Introduction to the Regmap data structures

The Regmap framework, which is enabled via the CONFIG_REGMAP kernel configuration option, is made of a few data structures, among which the most important are struct regmap_config, which represents the Regmap configuration, and struct regmap, which is the Regmap instance itself. That said, all of the Regmap data structures are defined in include/linux/regmap.h. It then goes without saying that this header must be included in all Regmap-based drivers:

#include <linux/regmap.h>

Including the preceding header is sufficient to make the most out of the Regmap framework. With this header, a lot of data structures will be made available, among which, struct regmap_config is the most important, which we will describe in the next section.

Understanding the struct regmap_config structure

struct regmap_config stores the configuration of the register map during the driver's lifetime. What you set there affects the memory read/write...