Linux Kernel Module Cheat

This example illustrates the most basic system calls: open, read, write, close and lseek.

In it we create a debugfs special file that behaves like a regular file, except that it is stored in memory for as long as the kernel module is loaded, and it has a fixed lengh of 4 bytes. Any longer write attempt gets simply truncated up at the end:

Outcome: the test passes:

Then give this a try:

We have put printks on each fop, so this allows you to see which system calls are being made for each command.

No, there no official documentation: https://stackoverflow.com/questions/15213932/what-are-the-struct-file-operations-arguments