What char devices and file_operations Expose to User Space
In Linux driver debugging, user space often sees a /dev/xxx node.
An application can open() it, read() from it, write() to it, or control it with ioctl(). It looks as if the device is a file.
But a char device is not “hardware handed directly to the application.” /dev/xxx is only a user-space entry. What actually decides what each call means is the char device object registered by the driver and its file_operations.