I was trying to make a serial driver for my project. It is suppose to support sending and receiving text messages between two computers to the serial COM1 port. My source code is basically based on Greg Kroah-Hartman's tinytty driver. As I was trying to use it, I came to realize that he didn't use any fops in his driver - which probably explains why I always get -1 from the write function. Can someone shed a light on this matter? Am I suppose to make a fops to become an interface between the user space? If that's the case, what would happen to the device file, since using uart_register_driver() already produces a device file. Any advice would be appreciated. Thanks!