linux - Linux 内核 4.8.0-53-generic Linux Mint 64 位中 IOCTL 函数的不兼容指针初始化错误

Question

我在使用 Ioctl 命令编写字符设备模块时遇到错误。

static struct file_operations my_fops =
{
    .unlocked_ioctl = my_ioctl, error is here. I can not fix this.
};

注意:请忽略我所有的print_k。

请帮我解决这个问题。感谢你们所有人。

这是我的代码:

static long my_ioctl(struct file *f,unsigned int cm,unsigned long arg[b]) 
{  
    int re; 
    unsigned long arg[3];

    switch (cm) 
    { 
        case H_ADD:          

          arg[2] = arg[0] + arg[1];  
          print_k("Driver:Calculating is complete,Result = %d \n",arg[2]); 
        break;  
        case H_SUB: 
          print_k ("Driver: Start ...\n"); 
          arg[2] = arg[0] - arg[1];  
          print_k("Driver:Calculating is complete,Result = %d \n",arg[2]);
        break; 
        case H_MULL:  
          print_k ("Driver: Start ...\n");  
          arg[2] = arg[0] * arg[1]; 
          print_k("Driver:Calculating is complete,Result = %d \n",arg[2]); 
        break; 
        case H_DIV:  
          print_k ("Driver: Start ...\n");  
          arg[2] = arg[0] / arg[1]; 
          print_k("Driver:Calculating is complete,Result = %d \n",arg[2]); 
        break; 
        default:  
          print_k ("Driver: I don't have this operation!\n"); 
        re = -Er; 
        break; 
        }  
    return re; 
} 

static struct file_operations my_fops =
{
    .unlocked_ioctl = my_ioctl, 
};

Answer 1

函数原型(prototype)中的第三个参数 unsigned long arg[b] 是可疑的。它应该只是unsigned long arg，即使它应该是一个指针。在函数体内将其转换为感兴趣的类型很容易。

..the optional arg argument is passed in the form of an unsigned long, regardless of whether it was given by the user as an integer or a pointer.

( Linux Device Drivers 3, Chapter 6, Section 1 )

此外，在函数体中声明一个与参数之一同名的变量是错误的。请为 unsigned long arg[3]; 选择另一个名称。