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 Device Drivers

Serial Peripheral Interface (SPI) is (at least) a four-wire bus: Master Input Slave Output (MISO); Master Output Slave Input (MOSI); Serial Clock (SCK); and Chip Select (CS), which is used to connect a serial flash, AD/DA converter. The master always generates the clock. Its speed can reach up to 80 MHz, even if there is no real speed limitation (much faster than I2C as well). The same for the CS line, which is always managed by the master.

Each of these signal names has a synonym:

  • Whenever you see SIMO, SDI, DI, or SDA, they refer to MOSI.
  • SOMI, SDO, DO, SDA will refer to MISO.
  • SCK, CLK, SCL will refer to SCK.
  • S̅ S̅ is the slave select line, also called the CS. CSx can be used (where x is an index, CS0, CS1); EN and ENB too, meaning enable. The CS is usually an active low signal:
SPI topology (image from wikipedia)

This chapter will walk...