linux-device-driver Getting started with linux-device-driver Hello World device driver

Example

hello_world.c

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>

#define AUTHOR  "Bruce Lee"
#define DESC    "Hello World driver"

static int __init init(void)
{
    printk(KERN_DEBUG "Hello World\n");
    return 0;
}

static void __exit deinit(void)
{
    printk(KERN_DEBUG "Goodbye World\n");
}

module_init(init);
module_exit(deinit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR(AUTHOR);
MODULE_DESCRIPTION(DESC);

Makefile:

KDIR ?= /lib/modules/`uname -r`/build
obj-m += hello_world.o

all:
        make -C $(KDIR) M=$(PWD) modules

clean:
        make -C $(KDIR) M=$(PWD) clean

How to compile:

$ make

How to insert the module:

$ sudo insmod hello_world.ko

How to see print messages

$ dmesg

How to list module/s

$ lsmod | grep hello_worls

How to remove the module

$ sudo rmmod hello_world