C Language

Oct 16, 2019
Apr 22, 2020

Linux Driver development

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

#define MACRONAME (expression)

For example, in C


int x;
int *p;

Peek inside Kernel
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
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
Embedding Linux
1. Tool chains
2. Bootloaders
3. Memory Layout
Debugging drivers

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

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

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