[PATCH] kbuild: Add dtc flag test

[Elliot Berman <eberman@codeaurora.org>]

Host dtc may not support the same flags as kernel's copy of dtc. Test
if dtc supports each flag when the dtc comes from host.

Signed-off-by: Elliot Berman <eberman@codeaurora.org>
---
 scripts/Makefile.lib | 34 ++++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 841ac03..2722a67 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -274,25 +274,35 @@ quiet_cmd_gzip = GZIP    $@
 
 # DTC
 # ---------------------------------------------------------------------------
+ifeq ("$(origin DTC)", "command line")
+PHONY += $(DTC)
+dtc-option = $(call try-run, $(DTC) $1 -v,$1)
+else
+# Just add the flag. DTC is compiled later as a prerequisite, so there's no dtc
+# to test the flag against. This is okay because we're not testing flags which
+# aren't supported by in-kernel dtc to begin with.
+dtc-option = $1
+endif
+
 DTC ?= $(objtree)/scripts/dtc/dtc
-DTC_FLAGS += -Wno-interrupt_provider
+DTC_FLAGS += $(call dtc-option,-Wno-interrupt_provider)
 
 # Disable noisy checks by default
 ifeq ($(findstring 1,$(KBUILD_EXTRA_WARN)),)
-DTC_FLAGS += -Wno-unit_address_vs_reg \
-	-Wno-unit_address_format \
-	-Wno-avoid_unnecessary_addr_size \
-	-Wno-alias_paths \
-	-Wno-graph_child_address \
-	-Wno-simple_bus_reg \
-	-Wno-unique_unit_address \
-	-Wno-pci_device_reg
+DTC_FLAGS += $(call dtc-option,-Wno-unit_address_vs_reg) \
+	$(call dtc-option,-Wno-unit_address_format) \
+	$(call dtc-option,-Wno-avoid_unnecessary_addr_size) \
+	$(call dtc-option,-Wno-alias_paths) \
+	$(call dtc-option,-Wno-graph_child_address) \
+	$(call dtc-option,-Wno-simple_bus_reg) \
+	$(call dtc-option,-Wno-unique_unit_address) \
+	$(call dtc-option,-Wno-pci_device_reg)
 endif
 
 ifneq ($(findstring 2,$(KBUILD_EXTRA_WARN)),)
-DTC_FLAGS += -Wnode_name_chars_strict \
-	-Wproperty_name_chars_strict \
-	-Winterrupt_provider
+DTC_FLAGS += $(call dtc-option,-Wnode_name_chars_strict) \
+	$(call dtc-option,-Wproperty_name_chars_strict) \
+	$(call dtc-option,-Winterrupt_provider)
 endif
 
 DTC_FLAGS += $(DTC_FLAGS_$(basetarget))
-- 
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