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

SPI user mode driver

There are two ways of using the user mode SPI device driver. To be able to do that, you need to enable your device with the spidev driver. An example would be as follows:

spidev@0x00 { 
    compatible = "spidev"; 
    spi-max-frequency = <800000>; /* It depends on your device */ 
    reg = <0>; /* correspond tochipselect 0 */ 
}; 

You can call either the read/write functions or an ioctl(). With calling read/write, you can only read or write at a time. If you need full-duplex read and write, you have to use the Input Output Control (ioctl) commands . Examples for both are provided. This is the read/write example. You can compile it either with the cross-compiler of the platform or with the native compiler on the board:

#include <stdio.h> 
#include <fcntl.h> 
#include <stdlib.h> 
 
int main(int argc, char...