a sample Linux driver 01

/*The drive test code as below*/

#include<stdio.h>
#include<fcntl.h>
#include<sys/types.h>
#include<sys/stat.h>


int main()
{
	int count = 0;
	int fd = NULL;
	unsigned char buf[100];
	unsigned char buf_read[100];
	memset(buf_read, 0, 100);
	memset(buf, 0, 100);
	fd = open("/dev/short_drv0", O_RDWR, S_IRUSR | S_IWUSR);

	printf("fd vlaue :%d\n", fd);
	printf("input string:");
	scanf("%s", buf);
//  const char * strTmp = "hello ryan, this is your first linux driver";
//    strncpy(buf, strTmp, strlen(strTmp));
	count = strlen(buf);
	if(count > 100)
		count = 100;
	count = write(fd, buf, count);

    read(fd,buf_read, count);

    printf("buf_read: %s\n", buf_read);

	close(fd);

    return 0;
}

/* Drive souce code as below*/

/*
	description: The relationship bewteeen user functions and kernel functions
*/

#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include<linux/module.h>
#include <linux/uaccess.h>
#include <linux/semaphore.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/ioctl.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/delay.h>
#include <linux/string.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>

#include <linux/platform_device.h>
#include <linux/version.h>
#include <linux/delay.h>
#include <linux/rfkill.h>





#define MAJOR_NUM 249
#define MINOR_NUM 0



static struct class		* short_class;
static struct cdev		short_cdev;
static dev_t devnum = 0;
static char * modname = "short_drv";
static char * devicename = "short_drv0";
static char * classname = "short_drv_class";
static struct semaphore sem;

static unsigned char kbuf[100] = {0};

static int short_open(struct inode *inode, struct file* pfile)
{
	printk(KERN_EMERG " + short_open() \n");
	return 0;
}

static int short_release(struct inode* inode, struct file *pfile)
{
	printk(KERN_EMERG "-short_rlease() \n");
 	 return 0;
}

ssize_t short_read (struct file *pfile, char *user_buf, size_t len, loff_t *off)
{
   	int iretval = len;

	if(len > 100)
		len = 100;

	copy_to_user(user_buf, kbuf, len);

	return iretval;
}
ssize_t short_write(struct file *pfile, const char *user_buf, size_t len, loff_t *off)
{

   	int iretval = len;

	if(len > 100)
		len = 100;

    printk("Ryan: %s\n",user_buf);
	copy_from_user(kbuf, user_buf, len);

	printk("user input string is :%s\n", kbuf);

	return iretval;

}


struct file_operations short_fops ={
	.open = short_open,
	.read = short_read,
	.write = short_write,
	.release = short_release,
};


static int __init short_drv_init(void)
{
	int result = 0;

	printk("short_drv_init(void) \n");

 	printk(KERN_EMERG " + short_drv_init(void) \n");

	devnum = MKDEV(MAJOR_NUM,MINOR_NUM); // get device number

	result = register_chrdev_region(devnum , 1, modname);

	if(result < 0)
	{
		printk( KERN_EMERG "short_drv_init : can't get major number!\n");
		return result;
	}

	cdev_init(&short_cdev, &short_fops);

	short_cdev.owner = THIS_MODULE;
	short_cdev.ops = &short_fops;

	result = cdev_add(&short_cdev, devnum ,1);
	if(result < 0)
	{
		printk( KERN_EMERG "cdev_add() execute failed!\n");
		return result;
	}

	short_class = class_create(THIS_MODULE, classname);
	if(IS_ERR(short_class))
	{
		printk( KERN_EMERG "Failed at class_create().Please exec [mknod] before operate the device\n");
	}
	else
	{
		device_create(short_class, NULL, devnum ,NULL, devicename);
	}

	sema_init(&sem, 1);

	printk( KERN_EMERG "-test_mod_init()!\n");


	return 0;
}


static void __exit short_drv_exit(void)
{

	printk( KERN_EMERG "+test_mod_exit!\n");

	unregister_chrdev_region(devnum, 1);

	cdev_del(&short_cdev);

	device_destroy(short_class, devnum);

	class_destroy(short_class);

	printk( KERN_EMERG "-test_mod_exit!\n");
}


module_init(short_drv_init);
module_exit(short_drv_exit);

MODULE_LICENSE("Dual BSD/GPL");

/*The driver makefile*/

ifneq ($(KERNELRELEASE),) 
	obj-m := short_drv.o 
else 
	KDIR:=/lib/modules/$(shell uname -r)/build 
	PWD:=$(shell pwd) 

all: 
	$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules 
endif 

clean: 
	rm -f *.o *.ko *.mod.c .short_drv*