--- bsd.port.mk	2011-08-23 06:59:56.418030776 +0200
+++ bsd.port.mk	2011-08-23 18:07:27.663775068 +0200
@@ -222,6 +222,16 @@ 
 #				- Set this instead of ONLY_FOR_ARCHS if the given port
 #				  fetches and installs compiled i386 binaries.
 #
+# ONLY_FOR_OSVER
+#				- A space-separated list of OS versions the port can be built on.
+#				  An OS version may be :
+#				   - a single value (e.g. 700000),
+#				   - a lower limit (e.g. 700000+),
+#				   - a higher limit (e.g. 800000-),
+#				   - a range (e.g. 700000-800000).
+# ONLY_FOR_OSVER_REASON
+#				- Reason why it's only for ${ONLY_FOR_OSVER}
+#
 # Dependency checking.  Use these if your port requires another port
 # not in the list below.  (Default: empty.)
 #
@@ -295,6 +305,12 @@ 
 #                         passed to the compiler by setting DEBUG_FLAGS. It is
 #                         set to "-g" at default.
 #
+##
+# USE_SRC		- If set, this port needs kernel sources to build.
+#				  If set to "yes", presence of ${SRC_BASE}/sys/Makefile
+#				  is checked. If set to a space-separated list of files,
+#				  presence of those files under ${SRC_BASE}/ is checked.
+##
 # USE_BZIP2		- If set, this port tarballs use bzip2, not gzip, for
 #				  compression.
 # USE_XZ		- If set, this port tarballs use xz (or lzma)
@@ -1361,6 +1377,29 @@ 
 WWWDIR?=		${PREFIX}/www/${PORTNAME}
 ETCDIR?=		${PREFIX}/etc/${PORTNAME}
 
+.if defined(USE_SRC)
+. if exists(${SRC_BASE}/sys/sys/param.h)
+_SRC_OSVERSION!=	${AWK} '/^\#define[[:blank:]]__FreeBSD_version/ {print $$3}' < ${SRC_BASE}/sys/sys/param.h
+.  if ${OSVERSION} != ${_SRC_OSVERSION}
+IGNORE=	requires source files for OS version ${OSVERSION}
+.  endif
+. endif
+
+. if !defined(${IGNORE})
+.  if ${USE_SRC:L} == "yes"
+_SRC_CHECK_FILES=	sys/Makefile
+.  else
+_SRC_CHECK_FILES=	${USE_SRC}
+.  endif
+
+.  for file in ${_SRC_CHECK_FILES}
+.   if !defined(${IGNORE}) && !exists(${SRC_BASE}/${file})
+IGNORE=	requires kernel source files
+.   endif
+.  endfor
+. endif
+.endif # defined(USE_SRC)
+
 .if defined(USE_LINUX_RPM)
 .include "${PORTSDIR}/Mk/bsd.linux-rpm.mk"
 .endif
@@ -3162,6 +3201,63 @@ 
 
 .endif
 
+# Check for OS version compatibility
+.if defined(ONLY_FOR_OSVER)
+
+# Sanity check
+_ONLY_FOR_OSVER_CHECK:=	${ONLY_FOR_OSVER:C/^[[:digit:]]+((-[[:digit:]]+)|[-+])?$//}
+
+. if (${_ONLY_FOR_OSVER_CHECK}x != "x")
+IGNORE=    invalid value specified for ONLY_FOR_OSVER: ${_ONLY_FOR_OSVER_CHECK}
+. else
+_ONLY_FOR_OSVER_IGNORE=	requires FreeBSD ${ONLY_FOR_OSVER}
+
+.  for version in ${ONLY_FOR_OSVER}
+_ONLY_FOR_OSVER:=	${version:C/\+$//}
+.   if ${_ONLY_FOR_OSVER} != "${version}"
+#  OSVERSION+ provided
+_ONLY_FOR_MIN_OSVER:=	${_ONLY_FOR_OSVER}
+.   else
+_ONLY_FOR_OSVER:=	${version:C/-$//}
+.    if ${_ONLY_FOR_OSVER} != "${version}"
+#   OSVERSION- provided
+_ONLY_FOR_MAX_OSVER:=	${_ONLY_FOR_OSVER}
+.    else
+_ONLY_FOR_OSVER:=	${version:C/-//}
+.     if ${_ONLY_FOR_OSVER} != "${version}"
+#    OSVERSION-OSVERSION range provided
+_ONLY_FOR_MIN_OSVER:=	${version:C/-.*$//}
+_ONLY_FOR_MAX_OSVER:=	${version:C/^.*-//}
+.     else
+#    single OSVERSION provided
+_ONLY_FOR_MIN_OSVER:=	${version}
+_ONLY_FOR_MAX_OSVER:=	${version}
+.     endif
+.    endif
+.   endif
+
+# Check OSVERSION against current requirements, one success is enough to continue
+.   if (!defined(_ONLY_FOR_MAX_OSVER) && (${OSVERSION} >= ${_ONLY_FOR_MIN_OSVER})) || \
+       (!defined(_ONLY_FOR_MIN_OSVER) && (${OSVERSION} <= ${_ONLY_FOR_MAX_OSVER})) || \
+       (defined(_ONLY_FOR_MIN_OSVER) && defined(_ONLY_FOR_MAX_OSVER) && \
+         (${OSVERSION} >= ${_ONLY_FOR_MIN_OSVER}) && (${OSVERSION} <= ${_ONLY_FOR_MAX_OSVER}))
+.    undef _ONLY_FOR_OSVER_IGNORE
+.   endif
+
+.   undef _ONLY_FOR_OSVER
+.   undef _ONLY_FOR_MIN_OSVER
+.   undef _ONLY_FOR_MAX_OSVER
+.  endfor
+
+.  if defined(_ONLY_FOR_OSVER_IGNORE)
+IGNORE=	${_ONLY_FOR_OSVER_IGNORE}
+.   if defined(ONLY_FOR_OSVER_REASON)
+IGNORE+= (${ONLY_FOR_OSVER_REASON})
+.   endif
+.  endif
+. endif
+.endif # defined(ONLY_FOR_OSVER)
+
 # Check the user interaction and legal issues
 .if !defined(NO_IGNORE)
 .if (defined(IS_INTERACTIVE) && defined(BATCH))