This document provides an introduction and overview of Linux device drivers. It discusses what a device driver is and its role in interfacing between operating systems, applications, and hardware. It covers setting up the development environment, writing a basic "hello world" driver as an example, loading and unloading modules, and next steps such as implementing file operations and using functions like copy_from/to_user. The goal is to help readers get started with developing their own Linux device drivers.

1. Linux Device Driver
for Dummies
2016/2

2. • What’s device driver?
• Setup
• Hello, device driver world!
• The next steps to driver developer

3. What is device driver?

4. •
OS
Application
Hardware
device driver

5. •
•
•
•

6. …
• API
• printf() API only C
•
• ➡

7. Setup

8. •
• α
•
•
yum kernel-devel, kernel-headers
apt-get linux-headers-generic, linux-source

9. Hello, device driver world!

10. #include <linux/module.h>
#include <linux/init.h>
MODULE_LICENSE("Dual BSD/GPL");
static int hello_init(void) {
printk(KERN_ALERT "driver loaded.n");
return 0;
}
static void hello_exit(void) {
printk(KERN_ALERT "driver unloaded.n");
}
module_init(hello_init);
module_exit(hello_exit);

11. #include <linux/module.h>
#include <linux/init.h>
MODULE_LICENSE("Dual BSD/GPL");
static int hello_init(void) {
printk(KERN_ALERT "driver loaded.n");
return 0;
}
static void hello_exit(void) {
printk(KERN_ALERT "driver unloaded.n");
}
module_init(hello_init);
module_exit(hello_exit);

12. • stdio.h, iostream
#include <linux/module.h>
#include <linux/init.h>

13. •
MODULE_LICENSE("Dual BSD/GPL");
$ insmod hello.ko
$ dmesg | tail -1
[ XX.XXX] hello: module verification failed: signatureand/or required key missing -
tainting kernel

14. module_init()/exit()
•
• insmod/rmmod
• main()
•
module_init(hello_init);
module_exit(hello_exit);

15. .ko insmod, rmmod

16. .ko Makefile
• .ko Makefile
• -C dir
= make
obj-m := hello.o
all:
make -C /lib/modules/$(shell uname -r)/build M=$(CURDIR) modules
clean:
make -C /lib/modules/$(shell uname -r)/build M=$(CURDIR) clean

17. •
• KBuild/
KConfig

18. $ insmod hello.ko
$ dmesg | tail -1
[ XX.XXX] driver loaded
$ rmmod hello.ko
$ dmesg | tail -1
[ XX.XXX] driver unloaded

19. The next steps to driver
developer

20. …
mknod
struct file_operations
copy_{from/to}_user()

21. •
• mknod
$ ls -l /dev/ttyS0
crw-rw---- 1 root dialout 4, 64 2 29 16:39 /dev/ttyS0

22. • Linux
• MMU(Memory Management Unit)
•
• struct map_desc
•
Primula arch/arm/mach-epson13/epson13.c

23. •
•
ARM memcpy()
unsigned long copy_from_user(void *to, const void __user *from,
unsigned long n)
unsigned long copy_to_user(void __user *to, const void *from,
unsigned long n)

24. try! linux device driver