communication-between-kernel-module-and-process.md

Communication between kernel module and user process

Driver

Driver is installed in kernel. In order for process in userspace to access it, we need to create special device file with major number in file system. The driver module in turn register file system functions with the major number.

result = register_chrdev(memory_major, "memory", &memory_fops);

The result is pseudo file /proc/devices/memory . udev then create corresponding device file traditional /dev/memory

procfs file

Other way is to register using proc filesystem

create_proc_read_entry("hello_world", 0, NULL, hello_read_proc, NULL) 

So when user process read, write to the special file, kernel invokes relevant registered file system functions.

See example in

• http://www.tldp.org/LDP/lkmpg/2.6/html/lkmpg.html
• http://www.opensourceforu.com/2012/06/some-nifty-udev-rules-and-examples/