Now that fdtoverlay is part of the kernel build, start using it to test
the unitest overlays we have by applying them statically.

Some unittest overlays deliberately contain errors that unittest checks
for. These overlays will cause fdtoverlay to fail, and are thus not
included in the static_test.dtb.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/of/unittest-data/Makefile | 50 +++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/drivers/of/unittest-data/Makefile b/drivers/of/unittest-data/Makefile
index 009f4045c8e4..ece7dfd5cafa 100644
--- a/drivers/of/unittest-data/Makefile
+++ b/drivers/of/unittest-data/Makefile

@@ -38,3 +38,53 @@ DTC_FLAGS_testcases += -@
 
 # suppress warnings about intentional errors
 DTC_FLAGS_testcases += -Wno-interrupts_property
+
+# Apply overlays statically with fdtoverlay.  This is a build time test that
+# the overlays can be applied successfully by fdtoverlay.  This does not
+# guarantee that the overlays can be applied successfully at run time by
+# unittest, but it provides a bit of build time test coverage for those
+# who do not execute unittest.
+#
+# The overlays are applied on top of testcases.dtb to create static_test.dtb
+# If fdtoverlay detects an error than the kernel build will fail.
+# static_test.dtb is not consumed by unittest.
+#
+# Some unittest overlays deliberately contain errors that unittest checks for.
+# These overlays will cause fdtoverlay to fail, and are thus not included
+# in the static test:
+#			overlay.dtb \
+#			overlay_bad_add_dup_node.dtb \
+#			overlay_bad_add_dup_prop.dtb \
+#			overlay_bad_phandle.dtb \
+#			overlay_bad_symbol.dtb \
+#			overlay_base.dtb \
+
+apply_static_overlay := overlay_0.dtb \
+			overlay_1.dtb \
+			overlay_2.dtb \
+			overlay_3.dtb \
+			overlay_4.dtb \
+			overlay_5.dtb \
+			overlay_6.dtb \
+			overlay_7.dtb \
+			overlay_8.dtb \
+			overlay_9.dtb \
+			overlay_10.dtb \
+			overlay_11.dtb \
+			overlay_12.dtb \
+			overlay_13.dtb \
+			overlay_15.dtb \
+			overlay_gpio_01.dtb \
+			overlay_gpio_02a.dtb \
+			overlay_gpio_02b.dtb \
+			overlay_gpio_03.dtb \
+			overlay_gpio_04a.dtb \
+			overlay_gpio_04b.dtb
+
+quiet_cmd_fdtoverlay = FDTOVERLAY $@
+      cmd_fdtoverlay = $(objtree)/scripts/dtc/fdtoverlay -o $@ -i $^
+
+$(obj)/static_test.dtb: $(obj)/testcases.dtb $(addprefix $(obj)/,$(apply_static_overlay))
+	$(call if_changed,fdtoverlay)
+
+always-$(CONFIG_OF_OVERLAY) += static_test.dtb