6. Unresolved Symbols
The most common and most frustrating failure in loading an LKM is a bunch of error messages about unresolved symbols, like this:
msdos.o: unresolved symbol fat_date_unix2dos msdos.o: unresolved symbol fat_add_cluster1 msdos.o: unresolved symbol fat_put_super ...
There are actually a bunch of different problems that result in this symptom. In any case, you can get closer to the problem by looking at /proc/ksyms and confirming that the symbols in the message are indeed not in the list.
6.1. Some LKMs Prerequire Other LKMs
6.2. An LKM Must Match The Base Kernel
6.3. If You Run Multiple Kernels
6.4. SMP symbols
6.5. You Are Not Licensed To Access The Symbol
6.6. An LKM Must Match Prerequisite LKMs