Linux kernel and Device Driver( Example in how to make kernel module.)

1. Linux Device Driver

2. Agenda
 History & Why Linux kernel?
 Device Driver.
 Purpose & Design
 Kernel mode & User mode
 Development
 Application & API

3. History and Why Linux kernel?
 First developed by Linus Torvals.
 Linux base on UNIX standard.
 Workgroup for implement driver
& patch with kernel.org.
 ”Just for fun” - Linux Torvals
History.

4. Pupose & Design
 Connection between Hardware and Software.
 Design communicate on logical
layer ( Port : ttyS,lp,hd) and
physical layer(Handle stardard
of communication protocol).
 Linux kernel (.ko file type) &
Microsoft (.sys file type )
kernel( Monolithic,Micro,Hybird
)

5. Linux boot sequence on x86
x86 Real Mode
BIOS
Bootloader ( GRUB/LILO )
Real Mode Kernel
X86 Protected
Arch/x86/boot/pm.c Mode
Protected Mode kernel
The init Process
User Processes and Daemons
Booting up,Essential Linux Device Drivers-Venkateswaran.

6. User & Kernel mode.

Kernel Mode
 It can execute any CPU instruction and reference
any memory address. Kernel mode is generally
reserved for the lowest-level”.
 Most, ”trusted functions of the operating system”.

User Mode
 In User mode, the executing code has no ability to
directly access hardware or reference memory.
 Code running in user mode must delegate to
system APIs to access hardware or memory.
Understanding user & kernel mode,Coding Horror-Jeff Atwood

7. Development
 Linux System Call.
 Device Drivers Development Supporting device
drivers.
 Kernel Programming Environment.

8. Linux System Call
 Executing in kernel mode.
 Kernel mode recognize and particular action
is require from the device.
 Call to device routine which pass user
process to device routine.
 Device routine may be shared
simulataneously by user application

9. Device Drivers Development
Supporting device drivers.
 A set of routines that communicate with a hardware
device and provide a uniform interface to the operating
system kernel.
 A self-contained component that can be added to, or
removed from, the operating system dynamically.
 Management of data flow and c ontrol between user
programs and a peripheral device.
 A user-defined section of the kernel that allows a
program or a peripheral device to appear as a `` /dev
'' device to the rest of the system's software.
Write a Linux Hardware Device Driver.FreeSoftware Mag.

10. Device Driver Programming
% make
#include <linux/init.h>
#include <linux/module.h> make[1]: Entering directory `/usr/src/linux-2.6.10'
MODULE_LICENSE("Dual BSD/GPL"); CC [M] /home/ldd3/src/misc-modules/hello.o
Building modules, stage 2.
static int hello_init(void) MODPOST
{ CC
printk(KERN_ALERT "Hello, worldn");
/home/ldd3/src/misc-modules/hello.mod.o
return 0;
LD [M] /home/ldd3/src/misc-modules/hello.ko
}
make[1]: Leaving directory `/usr/src/linux-2.6.10'
static void hello_exit(void) % su
{ root# insmod ./hello.ko
printk(KERN_ALERT "Goodbye, cruel worldn"); Hello, world
} root# rmmod hello
Goodbye cruel world
module_init(hello_init);
root#
module_exit(hello_exit);
Linux kernel in a nutshell,3rd-Greg Kroah-Hartman