I'm am working on adding YAFFS to my OS's VFS.  I've looked at 
yaffs_vfs_single.c that's included with the YAFFS distribution and shows 
how YAFFS was added to the Linux VFS.

It seems to me that yaffs_vfs_single.c must implement things that are 
implemented in yaffsfs.c (YAFFS Direct).  So, is there a reason that a 
YAFFS VFS implementation can't make calls into YAFFS Direct?