C Language

Linux Driver development

#define

#define is a C preprocessor directive used to define macros.

#define MACRONAME (expression)

dereference/ indirection operator

For example, in C

1. we can declare a variable x that holds an integer value,
2. and a variable p that holds a pointer to an integer value in memory:

Essential Linux device drivers Toolbox

1. Peek inside Kernel
2. Kernel Facilities
   1. kernel threads
      1. are like user processes but they live in kernel space and have access to special kernel functions and data structures
   2. Kernel Interfaces
   3. Kernel APIs
3. Linux device model
   1. Character / char drivers -printers, watchdogs
   2. Serial drivers
      1. UARTS drivers
      2. TTY drivers
   3. Input drivers - keyboard, mouse
   4. USB drivers
      1. touch screens drivers
   5. Audio/ Video/ Block device drivers
   6. Network interface cards
   7. Wireless drivers - Bluetooth, Wifi, GPRS, CDMA
4. Embedding Linux
   1. Tool chains
   2. Bootloaders
   3. Memory Layout
5. Debugging drivers

Introduction

• What is linux? where is the official source and mailing list? Where is the official source?
• How to buid linux from source?
• Linux has lodable modules lsmod
• Kernel mode and user mode aka user/kernel space
  • to effectively implement time-sharing system
• peek Internals of kernel from pseudo fs proc usuallt mounted at / root

Kernel boot starts with the execution of real mode assembly code living in /arch/x86/boot directory

• How to create a new kernel thread?¹
  • #include <linux/kthread.h>

What are devices and drivers?

Schematics of device from vendor, Role of device driver?

• device nodes /dev
• drivers /sys
• useful abstractions provided by kernel by sysfs, kobjects, device classes, udev
• Hotplug and Coldplug? Whats the difference?
• SPI available in market today includes RF (radio frewquency) chips, smart card interfaces, EEPROM, RTC, touch sensor, ADCs
• Write a Makefile for your driver file
• Compilation would create a .ko file
• Load the .ko file
• Exporting/importing kernel symbol table

• nm - list symbols from object files

  kernel headers
  printk
  KERNEL_ALERT
  
  # Makefile
  obj-m
  

Footnotes

[^2]: