I think debugfs is in the kernel documentation. I did a search for "debugfs and greg" in the linux.kernel news group of google groups. Following is one link i found that gives some information http://groups-beta.google.com/group/linux.kernel/browse_frm/thread/fcde73a146b26ddc/d6d7f25c24685db4?q=debugfs+greg&rnum=3#d6d7f25c24685db4