dt-bindings: kbuild: Use DTB files for validation

Switch the DT validation to use DTB files directly instead of a DTS to
YAML conversion.

The original motivation for supporting validation on DTB files was to
enable running validation on a running system (e.g. 'dt-validate
/sys/firmware/fdt') or other cases where the original source DTS is not
available.

The YAML format was not without issues. Using DTBs with the schema type
information solves some of those problems. The YAML format relies on the
DTS source level information including bracketing of properties, size
directives, and phandle tags all of which are lost in a DTB file. While
standardizing the bracketing is a good thing, it does cause a lot of
extra warnings and churn to fix them.

Another issue has been signed types are not validated correctly as sign
information is not propagated to YAML. Using the schema type information
allows for proper handling of signed types. YAML also can't represent
the full range of 64-bit integers as numbers are stored as floats by
most/all parsers.

The DTB validation works by decoding property values using the type
information in the schemas themselves. The main corner case this does
not work for is matrix types where neither dimension is fixed. For
now, checking the dimensions in these cases are skipped.
Signed-off-by: Rob Herring <robh@kernel.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20220310160513.1708182-3-robh@kernel.org

Documentation/devicetree/bindings/Makefile

@@ -26,8 +26,7 @@ $(obj)/%.example.dts: $(src)/%.yaml check_dtschema_version FORCE
 	$(call if_changed,extract_ex)
 
 find_all_cmd = find $(srctree)/$(src) \( -name '*.yaml' ! \
-		-name 'processed-schema*' ! \
-		-name '*.example.dt.yaml' \)
+		-name 'processed-schema*' \)
 
 find_cmd = $(find_all_cmd) | grep -F "$(DT_SCHEMA_FILES)"
 CHK_DT_DOCS := $(shell $(find_cmd))
@@ -72,9 +71,9 @@ $(obj)/processed-schema.json: $(DT_DOCS) $(src)/.yamllint check_dtschema_version
 
 always-y += processed-schema.json
 always-$(CHECK_DT_BINDING) += $(patsubst $(srctree)/$(src)/%.yaml,%.example.dts, $(CHK_DT_DOCS))
-always-$(CHECK_DT_BINDING) += $(patsubst $(srctree)/$(src)/%.yaml,%.example.dt.yaml, $(CHK_DT_DOCS))
+always-$(CHECK_DT_BINDING) += $(patsubst $(srctree)/$(src)/%.yaml,%.example.dtb, $(CHK_DT_DOCS))
 
 # Hack: avoid 'Argument list too long' error for 'make clean'. Remove most of
 # build artifacts here before they are processed by scripts/Makefile.clean
 clean-files = $(shell find $(obj) \( -name '*.example.dts' -o \
-			-name '*.example.dt.yaml' \) -delete 2>/dev/null)
+			-name '*.example.dtb' \) -delete 2>/dev/null)

Documentation/devicetree/bindings/writing-schema.rst

@@ -120,20 +120,13 @@ project can be installed with pip::
 
     pip3 install dtschema
 
-Several executables (dt-doc-validate, dt-mk-schema, dt-validate) will be
-installed. Ensure they are in your PATH (~/.local/bin by default).
-
-dtc must also be built with YAML output support enabled. This requires that
-libyaml and its headers be installed on the host system. For some distributions
-that involves installing the development package, such as:
-
-Debian::
+Note that 'dtschema' installation requires 'swig' and Python development files
+installed first. On Debian/Ubuntu systems::
 
-  apt-get install libyaml-dev
+    apt install swig python3-dev
 
-Fedora::
-
-  dnf -y install libyaml-devel
+Several executables (dt-doc-validate, dt-mk-schema, dt-validate) will be
+installed. Ensure they are in your PATH (~/.local/bin by default).
 
 Running checks
 ~~~~~~~~~~~~~~

scripts/Makefile.lib

@@ -87,11 +87,6 @@ base-dtb-y := $(foreach m, $(multi-dtb-y), $(firstword $(call suffix-search, $m,
 
 always-y			+= $(dtb-y)
 
-ifneq ($(CHECK_DTBS),)
-always-y += $(patsubst %.dtb,%.dt.yaml, $(real-dtb-y))
-always-y += $(patsubst %.dtbo,%.dt.yaml, $(real-dtb-y))
-endif
-
 # Add subdir path
 
 extra-y		:= $(addprefix $(obj)/,$(extra-y))
@@ -347,12 +342,6 @@ cmd_dtc = $(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ;
 		-d $(depfile).dtc.tmp $(dtc-tmp) ; \
 	cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)
 
-$(obj)/%.dtb: $(src)/%.dts $(DTC) FORCE
-	$(call if_changed_dep,dtc)
-
-$(obj)/%.dtbo: $(src)/%.dts $(DTC) FORCE
-	$(call if_changed_dep,dtc)
-
 quiet_cmd_fdtoverlay = DTOVL   $@
       cmd_fdtoverlay = $(objtree)/scripts/dtc/fdtoverlay -o $@ -i $(real-prereqs)
 
@@ -360,22 +349,27 @@ $(multi-dtb-y): FORCE
 	$(call if_changed,fdtoverlay)
 $(call multi_depend, $(multi-dtb-y), .dtb, -dtbs)
 
+ifneq ($(CHECK_DTBS)$(CHECK_DT_BINDING),)
 DT_CHECKER ?= dt-validate
 DT_CHECKER_FLAGS ?= $(if $(DT_SCHEMA_FILES),-l $(DT_SCHEMA_FILES),-m)
 DT_BINDING_DIR := Documentation/devicetree/bindings
 DT_TMP_SCHEMA := $(objtree)/$(DT_BINDING_DIR)/processed-schema.json
 
 quiet_cmd_dtb_check =	CHECK   $@
-      cmd_dtb_check =	$(DT_CHECKER) $(DT_CHECKER_FLAGS) -u $(srctree)/$(DT_BINDING_DIR) -p $(DT_TMP_SCHEMA) $@
+      cmd_dtb_check =	$(DT_CHECKER) $(DT_CHECKER_FLAGS) -u $(srctree)/$(DT_BINDING_DIR) -p $(DT_TMP_SCHEMA) $@ || true
+endif
 
 define rule_dtc
 	$(call cmd_and_fixdep,dtc)
 	$(call cmd,dtb_check)
 endef
 
-$(obj)/%.dt.yaml: $(src)/%.dts $(DTC) $(DT_TMP_SCHEMA) FORCE
+$(obj)/%.dtb: $(src)/%.dts $(DTC) $(DT_TMP_SCHEMA) FORCE
 	$(call if_changed_rule,dtc)
 
+$(obj)/%.dtbo: $(src)/%.dts $(DTC) FORCE
+	$(call if_changed_dep,dtc)
+
 dtc-tmp = $(subst $(comma),_,$(dot-target).dts.tmp)
 
 # Bzip2

scripts/dtc/Makefile

@@ -17,20 +17,7 @@ fdtoverlay-objs	:= $(libfdt) fdtoverlay.o util.o
 
 # Source files need to get at the userspace version of libfdt_env.h to compile
 HOST_EXTRACFLAGS += -I $(srctree)/$(src)/libfdt
-
-ifeq ($(shell pkg-config --exists yaml-0.1 2>/dev/null && echo yes),)
-ifneq ($(CHECK_DT_BINDING)$(CHECK_DTBS),)
-$(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
-# To include <yaml.h> installed in a non-default path
-HOSTCFLAGS_yamltree.o := $(shell pkg-config --cflags yaml-0.1)
-# To link libyaml installed in a non-default path
-HOSTLDLIBS_dtc	:= $(shell pkg-config --libs yaml-0.1)
-endif
 
 # Generated files need one more search path to include headers in source tree
 HOSTCFLAGS_dtc-lexer.lex.o := -I $(srctree)/$(src)

scripts/dtc/update-dtc-source.sh

@@ -32,7 +32,7 @@ DTC_UPSTREAM_PATH=`pwd`/../dtc
 DTC_LINUX_PATH=`pwd`/scripts/dtc
 
 DTC_SOURCE="checks.c data.c dtc.c dtc.h flattree.c fstree.c livetree.c srcpos.c \
-		srcpos.h treesource.c util.c util.h version_gen.h yamltree.c \
+		srcpos.h treesource.c util.c util.h version_gen.h \
 		dtc-lexer.l dtc-parser.y"
 LIBFDT_SOURCE="fdt.c fdt.h fdt_addresses.c fdt_empty_tree.c \
 		fdt_overlay.c fdt_ro.c fdt_rw.c fdt_strerror.c fdt_sw.c \