$ uname -r

4.4.131-20200710.kylin.x86-generic

test1/hello$ cat Makefile

obj-m :=hello.o

KERNELDIR = /usr/src/kylin-headers-4.4.131-20200710-generic

PWD := $(shell pwd)

default:

$(MAKE) -C $(KERNELDIR)  M=$(PWD) modules

clean:

rm -f *.o *.mod.o *mod.c *.symvers *.order

$make

$sudo insmod hello.ko

$cat hello.c

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/fs.h>

#include <linux/init.h>

#include <linux/device.h>

#include <linux/gpio.h>

#include <linux/miscdevice.h>

#include <linux/delay.h>

#include <asm/irq.h>

#include <asm/io.h>

#include <asm/uaccess.h>

#define DEVICE_NAME "hello"

static struct class *hello_class;

static int hello_open(struct tty_struct *tty, struct file *filp)

{

    printk("open is successed!\n");

    return 0;

}

static int hello_read(struct file *file, char __user *userbuf, size_t bytes, loff_t *off)

{

    unsigned char buf[4];

    buf[0]=0x11;

    buf[1]=0x33;

    buf[2]=0x44;

    buf[3]=0x55;

    copy_to_user(userbuf, buf, sizeof(buf));

    return (sizeof(buf));

}

static struct file_operations hello_fops={

.owner = THIS_MODULE,

.read = hello_read,

.open = hello_open,

};

static int major;

static int hello_init(void)

{

    major=register_chrdev(0, DEVICE_NAME, &hello_fops);

    hello_class=class_create(THIS_MODULE, DEVICE_NAME);

    device_create(hello_class, NULL, MKDEV(major,0), NULL, "hello");

    printk(KERN_ALERT "hello init is successed!\n");

    return 0;

}

static void hello_exit(void)

{

  unregister_chrdev(major, DEVICE_NAME);

  device_destroy(hello_class, MKDEV(major,0));

  class_destroy(hello_class);

  printk(KERN_ALERT "Hello Goodbye, cruel world\n");

}

module_init(hello_init);

module_exit(hello_exit);

MODULE_LICENSE("Dual BSD/GPL");

MODULE_AUTHOR("Terry");

MODULE_DESCRIPTION("A simple hello module");

MODULE_ALIAS("A simplest module");