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 15: Digging into the IIO Framework

Industrial input/output (IIO) is a kernel subsystem dedicated to analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). With the growing numbers of sensors (measurement devices with analog-to-digital or digital-to-analog capabilities) with different code implementations, scattered across kernel sources, gathering them became necessary. That is what the IIO framework does, in a generic way. Jonathan Cameron and the Linux IIO community have been developing it since 2009. Accelerometers, gyroscopes, current/voltage measurement chips, light sensors, and pressure sensors all fall into the IIO family of devices.

The IIO model is based on device and channel architecture:

  • The device represents the chip itself, the top level of the hierarchy.
  • The channel represents a single acquisition line of the device. A device may have one or more channels. For example, an accelerometer is a device with three channels, one for...