字符设备的另一种注册方法

代码如下：

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/arch/regs-gpio.h>
#include <asm/hardware.h>
#include <linux/poll.h>
#include <linux/cdev.h>

/* 确定主设备号 */
static int major;
static struct class *cls;
static struct cdev my_cdev;

static int open(struct inode *inode, struct file *file)
{
	printk(" In 'open' 
");
	return 0;
}


/* 构造file_operations */
static struct file_operations fops = {
	.owner = THIS_MODULE,
	.open  = open,
};

static int cdev_init(void)
{
	dev_t devid;
	
	if (major) {
		devid = MKDEV(major, 0);
		register_chrdev_region(devid, 1, "cdev");  
	} else {
		/* 动态申请设备编号 */
		alloc_chrdev_region(&devid, 0, 1, "cdev"); 
		major = MAJOR(devid);                     
	}
	
	cdev_init(&my_cdev, &fops);
	cdev_add(&my_cdev, devid, 1);

	/* 创建类 */
	cls = class_create(THIS_MODULE, "cdev");
	/* 创建节点 /dev/cdev0 */
	class_device_create(cls, NULL, MKDEV(major, 0), NULL, "cdev0"); 
	
	return 0;
}

static void cdev_exit(void)
{
	class_device_destroy(cls, MKDEV(major, 0));
	class_destroy(cls);

	cdev_del(&my_cdev);
	unregister_chrdev_region(MKDEV(major, 0), 1);
}

module_init(cdev_init);
module_exit(cdev_exit);

MODULE_LICENSE("GPL");