字符设备驱动 以及Makefile

#include <linux/module.h>       // module_init  module_exit
#include <linux/init.h>         // __init   __exit
#include <linux/cdev.h>
#include <linux/fs.h>
#define MYMAJOR     200
#define MYNAME      "chardev_test_byHc"
 
 
//DEVICE ID
dev_t devid;
 
static int chardev_open(struct inode *inode, struct file *file)
{
    printk(KERN_INFO "chardev open\n");
    return 0;
}
 
static ssize_t chardev_read(struct file *file, char __user *buf,
          size_t size, loff_t *ppos)
{
    return 0;
}
 
 
static const struct file_operations chardev_fops = { 
 
    .open = chardev_open,
    .read = chardev_read,
};
 
static struct
{
    struct cdev cdev;
}chardev;
 
static int __init mymodule_init(void)
{   
    int ret = 0;
    printk(KERN_INFO "chrdev_init helloworld init\n");
    cdev_init(&chardev.cdev,&chardev_fops);
        
    alloc_chrdev_region(&devid,2,255,MYNAME);
    printk(KERN_INFO "MAJOR Number is %d\n",MAJOR(devid));
    printk(KERN_INFO "MINOR Number is %d\n",MINOR(devid));
    cdev_add(&chardev.cdev,devid,255);
        
    return 0;
}
static void __exit mymodule_exit(void)
{
    printk(KERN_INFO "chrdev_exit helloworld exit\n");
    cdev_del(&chardev.cdev);
    unregister_chrdev_region(devid,255);
 
}
 
 
module_init(mymodule_init);
module_exit(mymodule_exit);
 
// MODULE_xxx这种宏作用是用来添加模块描述信息
MODULE_LICENSE("GPL");              // 描述模块的许可证
MODULE_AUTHOR("Hanc");              // 描述模块的作者
MODULE_DESCRIPTION("module test");  // 描述模块的介绍信息
MODULE_ALIAS("alias xxx");          // 描述模块的别名信息
 

 

CURRENT = $(shell uname -r )
KERNEL_TARGET=hello_test
MODULE_NAME :=$(KERNEL_TARGET)
MODULE_SUF=.ko
PWD:=$(shell pwd)
OUTPUT=$(PWD)/
KDIR=/lib/modules/$(CURRENT)/build

INCLUDE=-I/usr/src/linux-headers-4.9.0-3-common/include 
EXTRA_CFLAGS = -Wall -g -DASD_KERNEL $(INCLUDE)
#ccflags-y+=$(shell if [ $(call cc-version) -ge 0490 ] ; then echo "-Wno-error=date-time -Wno-date-time"; fi ;)

obj-m:=$(MODULE_NAME).o
$(MODULE_NAME)-objs:=test.o
all:
	make -C $(KDIR) INCLUDE=$(INCLUDE) M=$(PWD) modules
clean:
	make -C $(KDIR) M=$(PWD) clean
.PHONY: modules clean