Question

I want a character device to flush as I write to it. How do I call the file_operation’s flush method?

Here’s some relevant code:

struct file_operations ent_fops = {
          .owner = THIS_MODULE,
          .read = ent_read,
          .write = ent_write,
};

I don’t define flush myself

ssize_t ent_write(struct file *filp, const char __user *buf, size_t count,loff_t *f_pos)
{
blah...
*(ent_fops.flush)(file);
blah...
}

The code wont compile, the error is that I’m sending flush too few arguments. I cant find any mention anywhere of it needing more than one.

Answer 1

You’re missing the pointer to the file lock owner. Try

*(ent_fops.flush)(filp, NULL);