nnpfs/xfs_message.h documentation

Hello everybody.  Does anybody know of API documentation for the 
nnpfs_message/attr.h (xfs_*.h on some unices) files?  I'm implementing the 
xfs char-device with a non-arla superstructure.  Thusfar the arlad code 
itself has provided a clean resource but I'd like to be certain about some 
structures and valid values.  For instance, does struct nnpfs_handle 
always correspond with cell, volume, vnode and unique?

My questions have been hitherto answered by the code (both arlad and the 
kernel device) but I'd like to corroborate with an existing documentation 
base.  These bits, of course, will be made available for future 
implementations.

Thank you,
   Kristaps