Lab3 - Linux Device Driver (version 1)

Implement Linux Device Driver Version 1 of hello1.c: no parameter

Objective: Build and Install a Sample device driver and then compile "hello" program to verify it.

Requirements:

Linux (CentOS) - You can download this linux flavor from link http://www.centos.org/
Used linux kernel version 2.6.20
Vmware Player / Vmware Server / Vmware Workstation

Procedure

Step 1

First go to the directory

$ cd /usr/src/kernels/linux-2.6.20.1/drivers/char

Then create a new directory examples in it using following command.

$ mkdir examples

Go into the created directory examples using following command.

$ cd examples

Now you need to create two files in this examples directory. One of them is Makefile and second one is hello1.c. Steps are as below.

$ vi Makefile

and write following line into that file.

obj-$(CONFIG_EXAMPLES) += hello1.o

Then save it using :wq command.

Snapshot 1

$ vi hello1.c

And write following sample driver programs in hello1.c.

/* Example Minimal Character Device Driver */

#include <linux/module.h>

static int __init hello_init(void)

{

printk("Hello Example Init\n");

return 0;

}

static void __exit hello_exit(void)

{

printk("Hello Example Exit\n");

}

module_init(hello_init);

module_exit(hello_exit);

MODULE_AUTHOR("Chris Hallinan");

MODULE_DESCRIPTION("Hello World Example");

MODULE_LICENSE("GPL");

Step 2

Go into the following directory to change the Kconfig file.

$ cd /usr/src/kernels/linux-2.6.20.1/drivers/char

Then first back up Kconfig file to Kconfig.old file.

$ cp Kconfig Kconfig.old

The following Snapshot shows the content of Kconfig.old file.

Snapshot 2

Then open file Kconfig using following command

$ vi Kconfig

And add the following lines in Kconfig to add new configuration. Also add + sign in beginning of those lines as shown below.

....

menu "Character devices"

+ config EXAMPLES

+ tristate "Enable Examples"

+ default M

+ ---help---

+ Enable compilation option for driver examples

config VT

....

Following Snapshot 3 shows the content of new Kconfig file.

Snapshot 3

Step 3

Modify the usr/src/linux/drivers/char/Makefile using following commands

$ cd /usr/src/linux-2.6.20.1/drivers/char

$ vi Makefile

Search Makefile for the name IPMI using -> /IPMI

Then add the following line as shown in Snapshot. Don’t put blank line after or before added line.

obj-$(CONFIG_EXAMPLES) += examples/

Snapshot 4

Step 4

Then go to the directory linux-2.6.20.1 using following command.

$ cd /usr/src/linux-2.6.20.1

Then first back up the .config file in .config.old using following command.

$ cp .config .config.old

Then edit the .config file as below.

$ make menuconfig

Then go to the Device Driver -> Character Devices -> Enable Examples
Use spacebar to change configuration to ‘M’ of ‘*’ for Enable Examples.

Snapshot 5

Step 5

Enter the following command to compile modules.

$ make modules

Snapshot 6

Step 6

The following command installs the module.

$ make modules_install

It shows many warning at the end but ignore it.
This command creates files hello1.mod.o and hello1.ko as shown in following Snapshot 6.

Snapshot 7

The Following Snapshot 8 shows the newly created files in examples folder other than Makefile and hello1.c.

Snapshot 8

Step 7

To load the module use modeprobe or insmod but hello1.c doesn’t have any dependencies. So use commad insmode which is inside directory /sbin/insmode. So first go into the directory examples and use the insmode as shown in Snapshot 9.

$ cd /usr/src/kernels/linux-2.6.20.1/drivers/char/examples

$ /sbin/insmod hello1.ko

Snapshot 9

To see if module is sucessfully loaded or not, write the lsmod command and use pipeline with grep command to filter out hello word file & check the result as shown in following Snapshot 10.

Snapshot 10

Step 9

To remove the module from kernel use rmmod as shown below and use lsmod command to check wheher module is removed or not.

Snapshot 11

Use modinfo to see the module information as shown below.

$ /sbin/modinfo /usr/src/linux-2.6.20.1/drivers/char/examples/hello1.ko

Snapshot 12