kbuild: Add support for DT binding schema checks

This adds the build infrastructure for checking DT binding schema
documents and validating dts files using the binding schema.

Check DT binding schema documents:
make dt_binding_check

Build dts files and check using DT binding schema:
make dtbs_check

Optionally, DT_SCHEMA_FILES can be passed in with a schema file(s) to
use for validation. This makes it easier to find and fix errors
generated by a specific schema.

Currently, the validation targets are separate from a normal build to
avoid a hard dependency on the external DT schema project and because
there are lots of warnings generated.

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: linux-doc@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-kbuild@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>

.gitignore

@@ -15,6 +15,7 @@
 *.bin
 *.bz2
 *.c.[012]*.*
+*.dt.yaml
 *.dtb
 *.dtb.S
 *.dwo

Documentation/Makefile

@@ -2,7 +2,7 @@
 # Makefile for Sphinx documentation
 #
 
-subdir-y :=
+subdir-y := devicetree/bindings/
 
 # You can set these variables from the command line.
 SPHINXBUILD   = sphinx-build

Documentation/devicetree/bindings/.gitignore

+*.example.dts
+processed-schema.yaml

Documentation/devicetree/bindings/Makefile

+# SPDX-License-Identifier: GPL-2.0
+DT_DOC_CHECKER ?= dt-doc-validate
+DT_EXTRACT_EX ?= dt-extract-example
+DT_MK_SCHEMA ?= dt-mk-schema
+DT_MK_SCHEMA_FLAGS := $(if $(DT_SCHEMA_FILES), -u)
+
+quiet_cmd_chk_binding = CHKDT   $(patsubst $(srctree)/%,%,$<)
+      cmd_chk_binding = $(DT_DOC_CHECKER) $< ; \
+                        $(DT_EXTRACT_EX) $< > $@
+
+$(obj)/%.example.dts: $(src)/%.yaml FORCE
+	$(call if_changed,chk_binding)
+
+DT_TMP_SCHEMA := processed-schema.yaml
+extra-y += $(DT_TMP_SCHEMA)
+
+quiet_cmd_mk_schema = SCHEMA  $@
+      cmd_mk_schema = $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(filter-out FORCE, $^)
+
+DT_DOCS = $(shell cd $(srctree)/$(src) && find * -name '*.yaml')
+DT_SCHEMA_FILES ?= $(addprefix $(src)/,$(DT_DOCS))
+
+extra-y += $(patsubst $(src)/%.yaml,%.example.dts, $(DT_SCHEMA_FILES))
+extra-y += $(patsubst $(src)/%.yaml,%.example.dtb, $(DT_SCHEMA_FILES))
+
+$(obj)/$(DT_TMP_SCHEMA): $(DT_SCHEMA_FILES) FORCE
+	$(call if_changed,mk_schema)

Makefile

@@ -1232,10 +1232,13 @@ ifneq ($(dtstree),)
 %.dtb: prepare3 scripts_dtc
 	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
 
-PHONY += dtbs dtbs_install
-dtbs: prepare3 scripts_dtc
+PHONY += dtbs dtbs_install dt_binding_check
+dtbs dtbs_check: prepare3 scripts_dtc
 	$(Q)$(MAKE) $(build)=$(dtstree)
 
+dtbs_check: export CHECK_DTBS=1
+dtbs_check: dt_binding_check
+
 dtbs_install:
 	$(Q)$(MAKE) $(dtbinst)=$(dtstree)
 
@@ -1249,6 +1252,9 @@ PHONY += scripts_dtc
 scripts_dtc: scripts_basic
 	$(Q)$(MAKE) $(build)=scripts/dtc
 
+dt_binding_check: scripts_dtc
+	$(Q)$(MAKE) $(build)=Documentation/devicetree/bindings
+
 # ---------------------------------------------------------------------------
 # Modules
 
@@ -1611,7 +1617,8 @@ clean: $(clean-dirs)
 	$(call cmd,rmfiles)
 	@find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
 		\( -name '*.[aios]' -o -name '*.ko' -o -name '.*.cmd' \
-		-o -name '*.ko.*' -o -name '*.dtb' -o -name '*.dtb.S' \
+		-o -name '*.ko.*' \
+		-o -name '*.dtb' -o -name '*.dtb.S' -o -name '*.dt.yaml' \
 		-o -name '*.dwo' -o -name '*.lst' \
 		-o -name '*.su'  \
 		-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \

scripts/Makefile.lib

@@ -61,6 +61,11 @@ real-obj-m := $(foreach m, $(obj-m), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y))
 extra-y				+= $(dtb-y)
 extra-$(CONFIG_OF_ALL_DTBS)	+= $(dtb-)
 
+ifneq ($(CHECK_DTBS),)
+extra-y += $(patsubst %.dtb,%.dt.yaml, $(dtb-y))
+extra-$(CONFIG_OF_ALL_DTBS) += $(patsubst %.dtb,%.dt.yaml, $(dtb-))
+endif
+
 # Add subdir path
 
 extra-y		:= $(addprefix $(obj)/,$(extra-y))
@@ -284,13 +289,28 @@ $(obj)/%.dtb.S: $(obj)/%.dtb FORCE
 quiet_cmd_dtc = DTC     $@
 cmd_dtc = mkdir -p $(dir ${dtc-tmp}) ; \
 	$(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
-	$(DTC) -O dtb -o $@ -b 0 \
+	$(DTC) -O $(2) -o $@ -b 0 \
 		$(addprefix -i,$(dir $<) $(DTC_INCLUDE)) $(DTC_FLAGS) \
 		-d $(depfile).dtc.tmp $(dtc-tmp) ; \
 	cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)
 
 $(obj)/%.dtb: $(src)/%.dts $(DTC) FORCE
-	$(call if_changed_dep,dtc)
+	$(call if_changed_dep,dtc,dtb)
+
+DT_CHECKER ?= dt-validate
+DT_BINDING_DIR := Documentation/devicetree/bindings
+DT_TMP_SCHEMA := $(objtree)/$(DT_BINDING_DIR)/processed-schema.yaml
+
+quiet_cmd_dtb_check =	CHECK   $@
+      cmd_dtb_check =	$(DT_CHECKER) -p $(DT_TMP_SCHEMA) $@ ;
+
+define rule_dtc_dt_yaml
+	$(call cmd_and_fixdep,dtc,yaml)		\
+	$(call echo-cmd,dtb_check) $(cmd_dtb_check)
+endef
+
+$(obj)/%.dt.yaml: $(src)/%.dts $(DTC) $(DT_TMP_SCHEMA) FORCE
+	$(call if_changed_rule,dtc_dt_yaml)
 
 dtc-tmp = $(subst $(comma),_,$(dot-target).dts.tmp)
 

scripts/dtc/Makefile

@@ -12,6 +12,10 @@ dtc-objs	+= dtc-lexer.lex.o dtc-parser.tab.o
 HOST_EXTRACFLAGS := -I$(src)/libfdt
 
 ifeq ($(wildcard /usr/include/yaml.h),)
+ifneq ($(CHECK_DTBS),)
+$(error dtc needs libyaml for DT schema validation support. \
+	Install the necessary libyaml development package.)
+endif
 HOST_EXTRACFLAGS += -DNO_YAML
 else
 dtc-objs	+= yamltree.o