[PATCH 1/2] dt-bindings: Fix command line length limit calling dt-mk-schema

[Rob Herring]

As the number of schemas has increased, we're starting to hit the error
"execvp: /bin/sh: Argument list too long". This is due to passing all the
schema files on the command line to dt-mk-schema. It currently is only
with out of tree builds and is intermittent depending on the file path
lengths.

Commit 2ba06cd8565b ("kbuild: Always validate DT binding examples") made
hitting this proplem more likely since the example validation now always
gets the full list of schemas.

Fix this by putting the schema file list into a temp file and using xargs.

Reported-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
---
 Documentation/devicetree/bindings/.gitignore | 2 +-
 Documentation/devicetree/bindings/Makefile   | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/.gitignore b/Documentation/devicetree/bindings/.gitignore
index 5c6d8ea1a09c..0a6aef915fa4 100644
--- a/Documentation/devicetree/bindings/.gitignore
+++ b/Documentation/devicetree/bindings/.gitignore
@@ -1,3 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
 *.example.dts
-processed-schema*.yaml
+processed-schema*.yaml*
diff --git a/Documentation/devicetree/bindings/Makefile b/Documentation/devicetree/bindings/Makefile
index 1df680d07461..1c1cad860b7c 100644
--- a/Documentation/devicetree/bindings/Makefile
+++ b/Documentation/devicetree/bindings/Makefile
@@ -14,7 +14,8 @@ $(obj)/%.example.dts: $(src)/%.yaml FORCE
 DT_TMP_SCHEMA := $(obj)/processed-schema-examples.yaml
 
 quiet_cmd_mk_schema = SCHEMA  $@
-      cmd_mk_schema = $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(real-prereqs)
+      cmd_mk_schema = $(file >$@.tmp, $(real-prereqs)) \
+                      cat $@.tmp | xargs $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@
 
 DT_DOCS = $(addprefix $(src)/, \
 	$(shell \
-- 
2.20.1