为什么会有不兼容的指针类型警告？

Question

我正在使用内核3.13.0编写Linux设备驱动程序，但对于为什么收到此警告感到困惑。

warning: initialization from incompatible pointer type [enabled by default]
     .read = read_proc,
     ^
warning: (near initialization for ‘proc_fops.read’) [enabled by default]

据我所知，proc函数的file_operations设置与设备函数相同。我可以读/写到/ dev / MyDevice，没有任何问题，也没有警告。proc写入功能不会引发警告，而只会发出读取警告。我做错什么了？

/*****************************************************************************/
//DEVICE OPERATIONS
/*****************************************************************************/ 
static ssize_t dev_read(struct file *pfil, char __user *pBuf, size_t
  len, loff_t *p_off)
{
    //Not relevant to this question
}

static ssize_t dev_write(struct file *pfil, const char __user *pBuf,
                         size_t len, loff_t *p_off)
{
    //Not relevant to this question
}

static struct file_operations dev_fops =
{ //None of these cause a warning but the code is identical the proc code below
    .owner = THIS_MODULE,
    .read = dev_read,
    .write = dev_write
};

/*****************************************************************************/
//PROCESS OPERATIONS
/*****************************************************************************/
static int read_proc(struct file *pfil, char __user *pBuf, size_t
              len, loff_t *p_off)
{
    //Not relevant to this question
}

static ssize_t write_proc(struct file *pfil, const char __user *pBuf,
                         size_t len, loff_t *p_off)
{
    //Not relevant to this question
}

struct file_operations proc_fops = 
{
    .owner = THIS_MODULE,
    .write = write_proc,
    .read = read_proc, //This line causes the warning.
};

编辑：所以答案是我是白痴，看不到“ int”和“ ssize_t”。谢谢大家！Codenheim和Andrew Medico大致在同一时间都给出了正确答案，但我选择Medico，因为它对未来的访客来说更加有趣和明显。

Answer 1

您的read_proc函数的返回类型（引发警告）与完全编译的函数不匹配。

static ssize_t dev_read(struct file *pfil, char __user *pBuf, size_t len, loff_t *p_off)

与

static int read_proc(struct file *pfil, char __user *pBuf, size_t len, loff_t *p_off)

ssize_t且int大小可能不同。您函数的返回类型应为ssize_t。