Proper way to detect kernel / userland sources?

[Lev Serebryakov]

Hello, Ports.

  I'm  preparing port which depends both on kernel source (it contains
kernel module) and userland sources (it needs GEOM sources).

  I   see,   that  ports  with  kernel  modules  check  for  hardcoded
  "/usr/src/sys/Makefile".  But it doesn't look good: sources could be
  perfectly valid, but placed in other directory!

  Is  here  any  standerd  variable  which  should  be used instead of
  hardcoded "/usr/src"?

-- 
// Black Lion AKA Lev Serebryakov <lev at FreeBSD.org>