title: building kernel module and resolve missing symbol definitions
body: <p>If I build a module which depends on other modules, and i get this warning:</p>
  
  <blockquote>
    <p>'function or symbol ?' [source dir/my_module.ko] undefined!</p>
  </blockquote>
  
  <p>What does the warning mean? 
  The warning doesn't tell me if it is a function defined in a header or in some module source.  I suppose this means some module symbol definition is missing . So do I have to rebuild all modules on which my module is depending?</p>
  
  <p>Or may I somehow insert explicit symbols in my module source or in the makefile - for instance if I include the *.c source file where the missing symbols are defined in my module source? So to say - build my module without the need to build extra object files not in my source directory, on which my module depends.</p>
  
  <p>Thanks in advance!</p>