[PATCH] dt-bindings: kbuild: Support single binding targets

["Rob Herring (Arm)" <robh@kernel.org>]

Running the full 'make dt_binding_check' is slow. A shortcut is to set
DT_SCHEMA_FILES env variable to a substring of DT schema files to test.
It both limits which examples are validated and which schemas are used
to validate the examples. This is a problem because errors from other
schemas are missed. What makes validation slow is checking all examples,
so we really just need a way to test a single example.

Add a %.yaml target to validate the schema and validate the example:

make example-schema.yaml

The behavior for 'make dt_binding_check DT_SCHEMA_FILES=example-schema'
is unchanged. Really it should mirror dtbs_check and validate all the
examples with a subset of schemas, but there are lots of users of
expecting the existing behavior.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
---
 Documentation/devicetree/bindings/Makefile         |  5 ++++-
 .../devicetree/bindings/writing-schema.rst         | 12 ++++++++----
 Makefile                                           | 14 ++++++++++----
 3 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/Documentation/devicetree/bindings/Makefile b/Documentation/devicetree/bindings/Makefile
index 8d6f85f4455d..1e116425ad70 100644
--- a/Documentation/devicetree/bindings/Makefile
+++ b/Documentation/devicetree/bindings/Makefile
@@ -82,5 +82,8 @@ clean-files = $(shell find $(obj) \( -name '*.example.dts' -o \
 dt_compatible_check: $(obj)/processed-schema.json
 	$(Q)$(srctree)/scripts/dtc/dt-extract-compatibles $(srctree) | xargs dt-check-compatible -v -s $<
 
+PHONY += dt_binding_check_one
+dt_binding_check_one: $(obj)/.dt-binding.checked $(obj)/.yamllint.checked
+
 PHONY += dt_binding_check
-dt_binding_check: $(obj)/.dt-binding.checked $(obj)/.yamllint.checked $(CHK_DT_EXAMPLES)
+dt_binding_check: dt_binding_check_one $(CHK_DT_EXAMPLES)
diff --git a/Documentation/devicetree/bindings/writing-schema.rst b/Documentation/devicetree/bindings/writing-schema.rst
index 05c34248e544..2ff5b0565a31 100644
--- a/Documentation/devicetree/bindings/writing-schema.rst
+++ b/Documentation/devicetree/bindings/writing-schema.rst
@@ -214,6 +214,10 @@ binding schema. All of the DT binding documents can be validated using the
 
     make dt_binding_check
 
+Or to validate a single schema and its example::
+
+    make sram/sram.yaml
+
 In order to perform validation of DT source files, use the ``dtbs_check`` target::
 
     make dtbs_check
@@ -226,10 +230,10 @@ It is possible to run both in a single command::
 
     make dt_binding_check dtbs_check
 
-It is also possible to run checks with a subset of matching schema files by
-setting the ``DT_SCHEMA_FILES`` variable to 1 or more specific schema files or
-patterns (partial match of a fixed string). Each file or pattern should be
-separated by ':'.
+It is also possible to combine running the above commands with a subset of
+matching schema files by setting the ``DT_SCHEMA_FILES`` variable to 1 or more
+specific schema files or patterns (partial match of a fixed string). Each file
+or pattern should be separated by ':'.
 
 ::
 
diff --git a/Makefile b/Makefile
index 2f545ec1690f..1ae6b4c51955 100644
--- a/Makefile
+++ b/Makefile
@@ -1506,6 +1506,12 @@ ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/boot/dts/),)
 dtstree := arch/$(SRCARCH)/boot/dts
 endif
 
+dtbindingtree := Documentation/devicetree/bindings
+
+%.yaml: dtbs_prepare
+	$(Q)$(MAKE) $(build)=$(dtbindingtree) \
+		    $(dtbindingtree)/$(patsubst %.yaml,%.example.dtb,$@) dt_binding_check_one
+
 ifneq ($(dtstree),)
 
 %.dtb: dtbs_prepare
@@ -1523,7 +1529,7 @@ dtbs: dtbs_prepare
 # dtbs_install depend on it as dtbs_install may run as root.
 dtbs_prepare: include/config/kernel.release scripts_dtc
 
-ifneq ($(filter dtbs_check, $(MAKECMDGOALS)),)
+ifneq ($(filter dtbs_check %.yaml, $(MAKECMDGOALS)),)
 export CHECK_DTBS=y
 endif
 
@@ -1556,14 +1562,14 @@ endif
 
 PHONY += dt_binding_check dt_binding_schemas
 dt_binding_check: dt_binding_schemas scripts_dtc
-	$(Q)$(MAKE) $(build)=Documentation/devicetree/bindings $@
+	$(Q)$(MAKE) $(build)=$(dtbindingtree) $@
 
 dt_binding_schemas:
-	$(Q)$(MAKE) $(build)=Documentation/devicetree/bindings
+	$(Q)$(MAKE) $(build)=$(dtbindingtree)
 
 PHONY += dt_compatible_check
 dt_compatible_check: dt_binding_schemas
-	$(Q)$(MAKE) $(build)=Documentation/devicetree/bindings $@
+	$(Q)$(MAKE) $(build)=$(dtbindingtree) $@
 
 # ---------------------------------------------------------------------------
 # Modules
-- 
2.51.0