How to add your linux driver module in a kernel

Use below steps to add your driver module in linux kernel. by adding your driver as a module you can load/unload it at your convenience and will not be a part of your kernel image. I have used hello driver to explain it.
Steps to follow
===========
1). Create your module directory in /kernel/drivers
Eg. mkdir hellodriver
2).  Create your file inside /kernel/drivers/hellodriver/  and add below functions and save it.
Write your driver init and exit function in hello.c file.

————————————————–
#include
#include

static int __init hello_module_init(void)
{
printk (“hello test app module init”);
return 0;
}
static int __exit hello_module_cleanup(void)
{

printk(“hello test app module cleanup “);
return 0;
}

module_init(hello_module_init);
module_exit(hello_module_cleanup);
MODULE_LICENSE(“GPL”);
—————————————————————————————-

3).  Create empty Kconfig file and Makefile in /kernel/drivers/hellodriver/
4). Add below entries in Kconfig

config HELLOTEST_APP
tristate “HelloTest App”
depends on ARM
default m
help
hellotest app

5). Add below entries in Makefile

obj-$(CONFIG_HELLOTEST_APP) +=hello.o

6). Modify the /kernel/drivers Kconfig and Makefile to support your module
7). Add below entry in /kernel/drivers/Kconfig file

source “drivers/hellodriver/Kconfig”

8). Add below entry in /kernel/drivers/Makefile file

obj-$(CONFIG_HELLOTEST_APP) +=hellodriver/

9).  Now go to kernel directory and give

make menuconfig ARCH=arm

Verify that your driver module entry is visible under Device Drivers  —>
For module entry it shows HelloTest App
Now recompile the kernel with your requirement  and give

sudo make ARCH=arm CROSS_COMPILE=your toolchain path-

10). Check the hello.o and hello.ko files are generated at /kernel/drivers/hellodriver/
If you want to make your module as a part of kernel image then you only need to change <*> HelloTest App the option in menuconfig and  recompile the kernel.
If you don’t want to make your module as a part of kernel image then you only need to change <> HelloTest App the option in menuconfig and  recompile the kernel.
This is a very simple example of adding a module in a kernel.
How to Load/Unload  module/s from the user space:
In user space, you can load the module as root by typing the following into the command line. insmod load the module into kernel space.
# insmod hello.ko

To see the module loaded you can do following:

# lsmod

To remove your module from the kernel space you can do followig:

#rmmod hello.ko