misc_device

linux kernel miscdevice编写，需要三步：

• 创建 struct file_operations 变量

• 创建 struct miscdevice 变量

• 注册/注销miscdevice

1. 创建 struct file_operations 变量

const struct file_operations xxx_fops = {
    .owner    = THIS_MODULE,
    .open     = xxx_open,
    .release  = xxx_release,
    .write    = xxx_write,
    .read     = xxx_read,
};

2. 创建 struct miscdevice 变量

struct miscdevice xxx_miscdevice = {
    .minor = SUB_DEVICE_NUMBER, // 子设备号，只要linux miscdevice没有使用的子设备号都可以
    .name  = "xxxDev",          // 设备文件名/dev/xxxDev
    .fops  = &xxx_fops,
};

3. 注册/注销miscdevice

misc_register(&xxx_miscdevice);  // 注册
misc_deregister(&xxx_miscdevice);// 注销