error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types] .read = dev_read, Linux

Question

我在 linux 的内核代码中遇到以下文件操作错误。

你能帮我确定这里出了什么问题吗？

代码：

struct GraphData{
 unsigned long addr;
 long time;
};
static int position = 0;
struct GraphData buffer[BUFFER_SIZE]; 


static int dev_open(struct inode *in,struct file *f);
static ssize_t dev_read(struct file *f,struct GraphData *out,size_t count);
static int dev_release(struct inode *inod,struct file *f);

static struct file_operations fops =
{
  .read = dev_read,
  .open = dev_open,
  .release = dev_release
};

static int dev_open(struct inode *in, struct file *f){
 printk(KERN_INFO " Device has been opened \n");
 return 0;
}

static int dev_release(struct inode *in, struct file *f){
  printk(KERN_INFO "Device successfully closed\n");
  return 0;
}
static ssize_t dev_read(struct file *f,struct GraphData *out, size_t count)
{
  int ret=0,i=0;

  for(i=0;i<BUFFER_SIZE;i++)
  {
    count = copy_to_user(&out[i],&buffer[i],sizeof(buffer[i]));


    if(count<0)
    {
        printk(KERN_ALERT "Copy!");
        ret = -1;
    }
  }
  return count;
}

内核程序有文件操作，设备可以传递一个缓冲区并将数据存储到缓冲区中

用户程序

#define SIZE 500
struct Buffer
{
  unsigned long addr;
  long time;
};
int main()
{
 struct Buffer buf[SIZE];
 int i=0;
 int errorFlag = 0;
 int fp = open("/proc/Probe",O_RDONLY);
 errorFlag = read(fp,buf,1);
    printf("Page Fault Address           Time\n");
 for(i=0;i<SIZE;i++)
 {
    //printf("Read worked the Page fault address is 0x%lx caught at time  %ld\n",buf[i].address,buf[i].time);
    printf("0x%lx           %ld\n",buf[i].addr,buf[i].time);
}
close(fp);
return 0;
}

用户程序打开文件描述符，从设备中读取并将缓冲区传递给内核设备以复制到其中。

错误：错误：从不兼容的指针类型初始化 [-Werror=incompatible-pointer-types] .read = dev_read, /home/csvb/OS/assign4/hello2.c:36:12: 注意：（接近‘fops.read’的初始化） cc1：一些警告被视为错误

Answer 1

Could you help me identify what's going wrong here? [...] Error: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types] .read = dev_read, /home/csvb/OS/assign4/hello2.c:36:12: note: (near initialization for ‘fops.read’) cc1: some warnings being treated as errors

诊断对我来说似乎很清楚。它将问题定位到文件 /home/csvb/OS/assign4/hello2.c 的第 36 行，在由 fops 标识的 object 的成员 read 的初始化中；具体来说，指定初始化.read = dev_read。 "Initialization from incompatible pointer type" 的意思就是它所说的：dev_read 的类型与 fops.read 的类型不兼容。这样的问题在默认情况下应该发出警告，但编译选项指示它会导致错误。

一般来说，您应该检查文档，或者至少 headers，了解您所针对的内核版本，以确定预期的内容，但即使不这样做也是安全的假设 none 个参数的类型应为 struct GraphData *。那肯定是不兼容了。

内核设备 driver 接口的这个特殊细节在内核 5.7 的最新预发布版中是相同的，因为它至少可以追溯到内核 2.4，但是，即使不知道哪个内核版本你的目标是，我有信心说字符设备的读取功能应该有这个签名：

ssize_t dev_read_fn(struct file *, char __user *, size_t, loff_t *);

此外，第二个参数的类型与您的函数不同，它需要四个个参数，而不是三个。

error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types] .read = dev_read, Linux

error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types] .read = dev_read, Linux

c

linux

kernel