【讯为Linux驱动开发】4.文件私有数据

前面关于设备号、设备节点、class类和device设备都是用全局变量定义的，多了以后难免杂乱。

所以可以创建一个设备结构体，把设备号、设备节点、class类和device设备都放进去。

struct device_test{
    dev_t dev_num;
    static int major = 0;
    static int minor = 0;
    struct cdev cdev_test;
    struct class *class;
    struct device *device;
    
    char kbuf[];
};

/* 然后定义结构体变量 */
struct device_test dev1;

【问】为什么这么做？？

可移植性更高

【问】以下操作是为了什么？

static int cdev_open(struct inode *inode, struct file *filp)
{
    file->private_data = &dev1; //指向设备结构体
    ......
}

static ssize_t cdev_read(struct file *filp, char __user *buf, size_t cnt, loff_t *offt)
{
    struct device_test *test_dev = (struct device_test *)file->private_data;
    .....
}

面向对象

【使用文件私有数据完善驱动模板】

struct device_test{
    dev_t dev_num;
    static int major = 0;
    static int minor = 0;
    struct cdev cdev_test;
    struct class *class;
    struct device *device;
    char kbuf[32] = "this is cdev_read!";  //模拟内核寄存器的数据
};

/* 然后定义结构体变量 */
struct device_test dev1;

struct file_operations cdev_file_operations = {
    .owner = THIS_MODULE;
    .open = cdev_open;
    .read = cdev_read;
    .write = cdev_write;
    .release = cdev_release;
}

static int moduleparam_init()
{
          int ret;
          /* 动态申请 */
           ret = alloc_chrdev_region(&dev1.dev_num,0,1，"HELLO");  
          //动态注册设备号成功，则打印
           if(ret<0){
                printk("alloc_chrdev_region error!\n");              
           }
           printk("alloc_chrdev_region ok\n");  
           dev1.major_num =MAJOR(dev1.dev_num); //将主设备号取出来
           dev1.minor_num = MINOR(dev1.dev_num);//将次设备号取出来
           printk("major_num = %d\n", dev1.major_num);//打印传入进来的主设备号
           printk("minor_num = %d\n", dev1.minor_num);//打印传入进来的次设备号
           
           dev1.cdev_test.owner = THIS_MODULE;
           cdev_init(dev1.cdev_test, &cdev_file_operations);
           cdev_add(&dev1.cdev_test, dev1.dev_num, 1);
           class = class_creat(THIS_MODULE, "test");
           device = device_creat( dev1.class,NULL, dev1.dev_num,,NULL,"test")                      
           return 0;
}

static int cdev_open(struct inode *inode, struct file *filp)
{
    /*****************************************/
    file->private_data = &dev1; //指向设备结构体
    return 0;
}

static ssize_t cdev_read(struct file *filp, char __user *buf, size_t cnt, loff_t *offt)
{
    /*****************************************/
    struct device_test *test_dev = (struct device_test *)file->private_data;
    /* 把这个数组的数据拷贝到寄存器中 */
    if(copy_to_user（buf, test_dev->kbuf, strlen(test_dev->kbuf)）!= 0);
    {
       printk("copy_to_user error !\n");
       return -1;
    }
    printk("cdev_read success\n");
    return 0;
}

static ssize_t cdev_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt)
{
    /*****************************************/
    struct device_test *test_dev = (struct device_test *)file->private_data;
    test_dev->kbuf = {0};
    if(copy_from_user( test_dev->kbuf, buf ,sizeof(buf))!= 0);
    {
       printk("copy_from_user error !\n");
       return -1;
    }
    printk("cdev_write success\n");
    return 0;            
}

static int cdev_release(struct inode *inode, struct file *filp)
{
    /*****************************************/
    file->private_data = &dev1; //指向设备结构体
    return 0;       
}

static void hello_exit(void)
{
  unregister_chrdev_region( dev1.dev_num,DEVICE_NUMBER);//注销设备号
  cdev_del(& dev1.cdev_test);  //销毁字符设备
  device_destroy( dev1.class, dev1.dev_num);
  class_destroy( dev1.class);
  printk("gooodbye! \n");
}