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

Chapter 9: Writing SPI Device Drivers

The Serial Peripheral Interface (SPI) is (at least) a 4-wire bus – Master Input Slave Output (MISO), Master Output Slave Input (MOSI), Serial Clock (SCK), and Chip Select (CS) – which is used to connect serial flash and analog-to-digital/digital-to-analog converters. The master always generates the clock. Its speed can reach up to 80 MHz, though there is no real speed limitation (this is much faster than I2C as well). The same applies to the CS line, which is always managed by the master.

Each of these signal names has a synonym:

  • Whenever you see Slave Input Master Output (SIMO), Slave Data Input (SDI), or Data Input (DI), they refer to MOSI.
  • Slave Output Master Input (SOMI), Slave Data Output (SDO), and Data Output (DO) refer to MISO.
  • Serial Clock (SCK), Clock (CLK), and Serial Clock (SCL) refer to SCK.
  • S̅ S̅ is the Slave Select line, also called CS. CSx can be used (where x is an index such as...