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

Programming with the regmap API

The regmap API is quite simple. There are only a few structures to know. The two most important structures of this API are struct regmap_config, which represents the configuration of the regmap, and struct regmap, which is the regmap instance itself. All of the regmap data structures are defined in include/linux/regmap.h.

regmap_config structure

struct regmap_config stores the configuration of the regmap during the driver's lifetime. What you set here affects read/write operations. It is the most important structure in the regmap API. The source looks like this:

struct regmap_config { 
    const char *name; 
 
    int reg_bits; 
    int reg_stride; 
    int pad_bits; 
    int val_bits;...