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

Understanding Linux kernel time management

Time is one of the most used resources in computer systems, right after memory. It is used to do almost everything: timer, sleep, scheduling, and many other tasks.

The Linux kernel includes software timer concepts to enable kernel functions to be invoked at a later time.

The concepts of clocksource, clockevent, and tick device

In the original Linux timer implementation, the main hardware timer was mainly used for timekeeping. It was also programmed to fire interrupts periodically at HZ frequency, whose corresponding period is called a jiffy (both are explained later in this chapter, in the Jiffies and HZ section). Each of these interrupts generated every 1/HZ second was (and still is) referred to as a tick. Throughout this section, the term tick will refer to the interrupt generated at a 1/HZ period.

The whole system time management (either from the kernel or user space) was bound to jiffies, which is also a global variable in...