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

Regulators consumer interface

The consumer interface only requires the driver to include one header:

#include <linux/regulator/consumer.h> 

A consumer can be static or dynamic. A static one requires only a fixed supply, whereas a dynamic one requires active management of the regulator at runtime. From the consumer point side, a regulator device is represented in the kernel as an instance of a struct regulator structure, defined in drivers/regulator/internal.h and shown as follows:

/* 
 * struct regulator 
 * 
 * One for each consumer device. 
 */ 
struct regulator { 
   struct device *dev; 
   struct list_head list; 
   unsigned int always_on:1; 
   unsigned int bypass:1; 
   int uA_load; 
   int min_uV; 
   int max_uV; 
   char *supply_name; 
   struct device_attribute dev_attr; 
   struct regulator_dev *rdev; 
   struct dentry *debugfs; 
}; 

This structure is meaningful...