• 项设备可以说是对一部分字符设备的封装，还有一部分不好归类驱
  动也归到杂项设备
• 杂项设备初始化部分源文件“drivers/char/ misc.c”，这一部分通过
  Makefile可知，是强制编译的。
• 杂项设备注册头文件include/linux/miscdevice.h
• 结构体miscdevice以及注册函数

struct miscdevice  {
        int minor;//设备号
        const char *name;//生成设备节点的名称
        const struct file_operations *fops;//指向一个设备节点文件
        struct list_head list;
        struct device *parent;
        struct device *this_device;
        const char *nodename;
        mode_t mode;
};
extern int misc_register(struct miscdevice * misc);
extern int misc_deregister(struct miscdevice *misc);

• 包含文件结构体的头文件是“include/linux/fs.h
• 文件的结构体file_operations

struct file_operations {
        struct module *owner;
        loff_t (*llseek) (struct file *, loff_t, int);
        ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
        ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
        ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
        ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
        int (*readdir) (struct file *, void *, filldir_t);
        unsigned int (*poll) (struct file *, struct poll_table_struct *);
        long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
        long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
        int (*mmap) (struct file *, struct vm_area_struct *);
        int (*open) (struct inode *, struct file *);
        int (*flush) (struct file *, fl_owner_t id);
        int (*release) (struct inode *, struct file *);
        int (*fsync) (struct file *, int datasync);
        int (*aio_fsync) (struct kiocb *, int datasync);
        int (*fasync) (int, struct file *, int);
        int (*lock) (struct file *, int, struct file_lock *);
        ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
        unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
        int (*check_flags)(int);
        int (*flock) (struct file *, int, struct file_lock *);
        ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
        ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
        int (*setlease)(struct file *, long, struct file_lock **);
        long (*fallocate)(struct file *file, int mode, loff_t offset,
                          loff_t len);
/* add by cym 20130408 support for MT6260 and Pixtree */
#if defined(CONFIG_SMM6260_MODEM) || defined(CONFIG_USE_GPIO_AS_I2C)
        int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
};

• 文件的结构体file_operations参数很多，根据需求选择

• 必选的是参数是
  .owner一般是THIS_MODULE,
  .open打开文件函数
  .release关闭文件函数

• 在/dev中查看是否生成了设备节点

• demo:

#include <linux/init.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>

#define DEVICE_NAME "hello_ctl123"
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("TOPEET");

static long hello_ioctl( struct file *files, unsigned int cmd, unsigned long arg)
{
	printk("cmd is %d,arg is %d\n",cmd,arg);
	return 0;
}

static int hello_release(struct inode *inode, struct file *file)
{
	printk(KERN_EMERG "hello release\n");
	return 0;
}

static int hello_open(struct inode *inode, struct file *file)
{
	printk(KERN_EMERG "hello open\n");
	return 0;
}

static struct file_operations hello_ops = {
	.owner = THIS_MODULE,
	.open = hello_open,
	.release = hello_release,
	.unlocked_ioctl = hello_ioctl,
};

static  struct miscdevice hello_dev = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = DEVICE_NAME,
	.fops = &hello_ops,
};

static int hello_init(void)
{
	printk(KERN_EMERG "HELLO WORLD enter!\n");
	misc_register(&hello_dev);
	
	return 0;
}

static void hello_exit(void)
{
	printk(KERN_EMERG "HELLO WORLD exit!\n");
	misc_deregister(&hello_dev);	
}

module_init(hello_init);
module_exit(hello_exit);

说明，这里的设备为hello_ctl123，如要注册这个驱动首先要注册这个设备。