Compile external module against linux source and use functionality in linux source

Hi I am trying to two things here. 1. Compile my module and export a function. 2. Use this exported function in modified kernel src and compile it. Step 1 goes through fine. The module gets compiled fine. However now when i try to compile the kernel i get linker error of undefined reference to the function exported from the kernel module. I can't find any documentation on this usecase. Thanks Arjun