Essential Linux Device Drivers

Sreekrishnan Venkateswaran has worked in IBM's Linux Product Development Labs for 10 years in Bangalore, Austin, Rochester and Raleigh. For the past six years he has been working on putting Linux on various devices like a wrist watch, a cell phone, an MP3 player, a PDA and a pacemaker. Prior to this, he developed ATM device drivers and networking protocols on AIX. He has also worked in software development for network processors and routers. Venkateswaran holds a Master's degree in Computer Science from the Indian Institute of Technology, Kanpur, India. He is currently a contributing editor and kernel columnist for Linux Magazine.

Foreword xxi

Preface xxiii

Acknowledgments  xxix

About the Author  xxx

Chapter 1 Introduction 1

Evolution  2

The GNU Copyleft  3

Kernelorg  4

Mailing Lists and Forums  4

Linux Distributions  5

Looking at the Sources  6

Building the Kernel  10

Loadable Modules  12

Before Starting  14

Chapter 2 A Peek Inside the Kernel 17

Booting Up  18

Kernel Mode and User Mode  30

Process Context and Interrupt Context  30

Kernel Timers  31

HZ and Jiffies  31

Long Delays  33

Short Delays  36

Pentium Time Stamp Counter  36

Real Time Clock  37

Concurrency in the Kernel  39

Spinlocks and Mutexes  39

Atomic Operators  45

Reader-Writer Locks  46

Debugging  48

Process Filesystem  49

Allocating Memory  49

Looking at the Sources  52

Chapter 3 Kernel Facilities 55

Kernel Threads  56

Creating a Kernel Thread  56

Process States and Wait Queues  61

User Mode Helpers  63

Helper Interfaces  65

Linked Lists  65

Hash Lists  72

Work Queues  72

Notifier Chains  74

Completion Interface  78

Kthread Helpers  81

Error-Handling Aids  83

Looking at the Sources  85

Chapter 4 Laying the Groundwork 89

Introducing Devices and Drivers  90

Interrupt Handling  92

Interrupt Context  92

Assigning IRQs  94

Device Example: Roller Wheel  94

Softirqs and Tasklets  99

The Linux Device Model  103

Udev  103

Sysfs, Kobjects, and Device Classes  106

Hotplug and Coldplug  110

Microcode Download  111

Module Autoload  112

Memory Barriers  114

Power Management  114

Looking at the Sources  115

Chapter 5 Character Drivers 119

Char Driver Basics  120

Device Example: System CMOS  121

Driver Initialization  122

Open and Release  127

Exchanging Data  129

Seek  136

Control  137

Sensing Data Availability  139

Poll  139

Fasync  142

Talking to the Parallel Port  145

Device Example: Parallel Port LED Board  146

RTC Subsystem  156

Pseudo Char Drivers  157

Misc Drivers  160

Device Example: Watchdog Timer  160

Character Caveats  166

Looking at the Sources  167

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Chapter 6 Serial Drivers 171

Layered Architecture  173

UART Drivers  176

Device Example: Cell Phone  1...