Index: bsd.options.mk
===================================================================
--- bsd.options.mk	(revision 358421)
+++ bsd.options.mk	(working copy)
@@ -95,6 +95,10 @@
 # ${opt}_QMAKE_OFF		When option is disabled, it will add its content to
 #				the QMAKE_ARGS.
 #
+# ${opt}_ENABLES		When opt is enabled, options named in ENABLES will
+# 				get enabled too
+# ${opt}_PREVENTS		When opt is enabled, if any options in PREVENTS are
+# 				enabled, it will produce an error
 # ${opt}_USE=	FOO=bar		When option is enabled, it will  enable
 #				USE_FOO+= bar
 #				If you need more than one option, you can do
@@ -383,6 +387,22 @@
 NEW_OPTIONS:=	${NEW_OPTIONS:N${opt}}
 .endfor
 
+# Enable options implied by other options
+.for count in ${PORT_OPTIONS}
+.  for opt in ${PORT_OPTIONS}
+PORT_OPTIONS+=	${${opt}_ENABLES}
+.  endfor
+.endfor
+
+# Prevent options that conflict
+.for opt in ${PORT_OPTIONS}
+.  for conflict in ${${opt}_PREVENTS}
+.    if ${PORT_OPTIONS:M${conflict}}
+IGNORE=	Option ${conflict} conflicts with option ${opt}
+.    endif
+.  endfor
+.endfor
+
 # Finally, add options required by slave ports
 PORT_OPTIONS+=	${OPTIONS_SLAVE}