About the returned value of the driver

About the returned value of the driver-Linux general technology-Linux programming and kernel information, the following is a detailed description. Dear fellow students and beginners, I have never been very familiar with this. in general linux drivers, such as the compilation of open functions, return 0 at the end, however, the corresponding open function in the application returns a non-zero file descriptor value, according to the original understanding of the C language, the return value of a function should be its return value. I don't understand why the open function does not always return 0? What is the difference between the return value in other drivers, such as read, write, and ioctl, and the return value in the application? I hope you will be enlightened to familiarize yourself with linux programming as soon as possible!