Add CONF_ENABLE and CONF_PKG_ENABLE helper functions

index c9887c2..3743db3 100644
@@ -37,6 +37,63 @@ define CONFIG_UPDATE
 endef
 
 ################################################################################
+# CONFIG_ENABLE -- generates the configure option to enable or disable a
+# feature depending on a .config option.
+#
+# argument 1 is the uppercase package name
+# argument 2 is y or empty (i.e. it is the .config option to check)
+# argument 3 (optional) are additional dependencies in case the .config option
+#   is y.
+# If the call has four arguments, argument 4 is the name that comes behind
+#   --enable- resp. --disable-
+# If the call has five argument, argument 4 is the ensable option and
+#   argument 5 is the disable option.
+# The call must be done within an $(eval) clause.
+#
+# Examples:
+# $(eval $(call CONF_ENABLE,CAIRO,$(BR2_PACKAGE_CAIRO_SVG),,svg))
+# $(eval $(call CONF_ENABLE,CAIRO,$(BR2_PACKAGE_CAIRO_PNG),libpng,png))
+# $(eval $(call CONF_ENABLE,AVAHI,$(BR2_PACKAGE_AVAHI_DAEMON),expat,--with-xml=expat,--with-xml=none))
+#
+################################################################################
+define CONF_ENABLE
+ifeq ($(2),y)
+       $(1)_CONF_OPT += $(if $(5),$(4),--enable-$(4))
+       $(1)_DEPENDENCIES += $(3)
+else
+       $(1)_CONF_OPT += $(if $(5),$(5),--disable-$(4))
+endif
+endef
+
+################################################################################
+# CONF_PKG ENABLE -- generates the configure option and dependency for another
+# package, depending on whether that package is selected.  If the other package
+# is selected, an --enable- option and a dependency on the other package is
+# added.  If the other package is not selected, a --disable- option is added.
+#
+#  argument 1 is the uppercase package name
+#  argument 2 is the lowercase name of the other package
+#  If the call has two arguments, the --enable-<pkg> configure option is added.
+#  If the call has three arguments, argument 3 is the name that comes after
+#    --enable- and --disable- (in case this differs from the buildroot package
+#    name).
+#  If the call has four arguments, argument 3 is the option to enable the
+#    other package and argument 4 is the option to disable it.
+#
+# The call must be done within an $(eval) clause.
+#
+# Examples:
+# $(eval $(call CONF_PKG_ENABLE,AVAHI,dbus))
+# $(eval $(call CONF_PKG_ENABLE,AVAHI,libglade,gtk))
+# $(eval $(call CONF_PKG_ENABLE,AVAHI,libglib2,--enable-glib --enable-gobject,--disable-glib --disable-gobject))
+#
+################################################################################
+define CONF_PKG_ENABLE
+$(call CONF_ENABLE,$(1),$(BR2_PACKAGE_$(call UPPERCASE,$(2))),$(2),$(if $(3),$(3),$(2)),$(if $(4),$(4),))
+endef
+
+
+################################################################################
 # AUTOTARGETS_INNER -- defines how the configuration, compilation and
 # installation of an autotools package should be done, implements a
 # few hooks to tune the build process for autotools specifities and

index 32e3df7..64a83db 100644
@@ -91,31 +91,12 @@ else
 AVAHI_CONF_OPT += --disable-libdaemon
 endif
 
-ifeq ($(BR2_PACKAGE_AVAHI_DAEMON),y)
-AVAHI_DEPENDENCIES += expat
-AVAHI_CONF_OPT += --with-xml=expat
-else
-AVAHI_CONF_OPT += --with-xml=none
-endif
-
-ifeq ($(BR2_PACKAGE_DBUS),y)
-AVAHI_DEPENDENCIES += dbus
-else
-AVAHI_CONF_OPT += --disable-dbus
-endif
-
-ifeq ($(BR2_PACKAGE_LIBGLIB2),y)
-AVAHI_DEPENDENCIES += libglib2
-else
-AVAHI_CONF_OPT += --disable-glib --disable-gobject
-endif
-
-ifeq ($(BR2_PACKAGE_LIBGLADE),y)
-AVAHI_DEPENDENCIES += libglade
-else
-AVAHI_CONF_OPT += --disable-gtk
-endif
+$(eval $(call CONF_ENABLE,AVAHI,$(BR2_PACKAGE_AVAHI_DAEMON),expat,--with-xml=expat,--with-xml=none))
+$(eval $(call CONF_PKG_ENABLE,AVAHI,dbus))
+$(eval $(call CONF_PKG_ENABLE,AVAHI,libglib2,--enable-glib --enable-gobject,--disable-glib --disable-gobject))
+$(eval $(call CONF_PKG_ENABLE,AVAHI,libglade,gtk))
 
+$(eval $(call CONF_PKG_ENABLE,AVAHI,python))
 ifeq ($(BR2_PACKAGE_PYTHON),y)
 AVAHI_CONF_ENV += am_cv_pathless_PYTHON=python \
 		am_cv_path_PYTHON=$(PYTHON_TARGET_BINARY) \

@@ -124,11 +105,6 @@ AVAHI_CONF_ENV += am_cv_pathless_PYTHON=python \
 		am_cv_python_pythondir=/usr/lib/python$(PYTHON_VERSION_MAJOR)/site-packages \
 		am_cv_python_pyexecdir=/usr/lib/python$(PYTHON_VERSION_MAJOR)/site-packages \
 		py_cv_mod_socket_=yes
-
-AVAHI_DEPENDENCIES += python
-AVAHI_CONF_OPT += --enable-python
-else
-AVAHI_CONF_OPT += --disable-python
 endif
 
 ifeq ($(BR2_PACKAGE_LIBINTL),y)

index 55068dd..5486372 100644
@@ -36,45 +36,13 @@ CAIRO_CONF_ENV = ac_cv_func_posix_getpwuid_r=yes glib_cv_stack_grows=no \
 
 CAIRO_DEPENDENCIES = host-pkg-config fontconfig pixman
 
-ifeq ($(BR2_PACKAGE_DIRECTFB),y)
-	CAIRO_CONF_OPT += --enable-directfb
-	CAIRO_DEPENDENCIES += directfb
-else
-	CAIRO_CONF_OPT += --disable-directfb
-endif
+$(eval $(call CONF_PKG_ENABLE,CAIRO,directfb))
 
-ifeq ($(BR2_PACKAGE_XORG7),y)
-	CAIRO_CONF_OPT += --enable-xlib --with-x
-	CAIRO_DEPENDENCIES += xserver_xorg-server
-else
-	CAIRO_CONF_OPT += --disable-xlib --without-x
-endif
+$(eval $(call CONF_ENABLE,CAIRO,$(BR2_PACKAGE_XORG7),xserver_xorg-server,--enable-xlib --with-x,--disable-xlib --without-x))
 
-ifeq ($(BR2_PACKAGE_CAIRO_PS),y)
-	CAIRO_CONF_OPT += --enable-ps
-	CAIRO_DEPENDENCIES += zlib
-else
-	CAIRO_CONF_OPT += --disable-ps
-endif
-
-ifeq ($(BR2_PACKAGE_CAIRO_PDF),y)
-	CAIRO_CONF_OPT += --enable-pdf
-	CAIRO_DEPENDENCIES += zlib
-else
-	CAIRO_CONF_OPT += --disable-pdf
-endif
-
-ifeq ($(BR2_PACKAGE_CAIRO_PNG),y)
-	CAIRO_CONF_OPT += --enable-png
-	CAIRO_DEPENDENCIES += libpng
-else
-	CAIRO_CONF_OPT += --disable-png
-endif
-
-ifeq ($(BR2_PACKAGE_CAIRO_SVG),y)
-	CAIRO_CONF_OPT += --enable-svg
-else
-	CAIRO_CONF_OPT += --disable-svg
-endif
+$(eval $(call CONF_ENABLE,CAIRO,$(BR2_PACKAGE_CAIRO_PS),zlib,ps))
+$(eval $(call CONF_ENABLE,CAIRO,$(BR2_PACKAGE_CAIRO_PDF),zlib,pdf))
+$(eval $(call CONF_ENABLE,CAIRO,$(BR2_PACKAGE_CAIRO_PNG),libpng,png))
+$(eval $(call CONF_ENABLE,CAIRO,$(BR2_PACKAGE_CAIRO_SVG),,svg))
 
 $(eval $(call AUTOTARGETS))