o (void) cast write return value in signal handler, but gcc still
  warns about the unused values.
  ... because gcc developers are pricks: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25509
o Add include guards.
o Use constant to denote the logical axis range (instead of constant
  8)
o Better naming of axis->driver array.
o introduce physical mapping of axis as well. That way the
  whatever physical layout of the board ca nbe mapped to a
  topography.