[PATCH] kbuild: Optionally enable schema checks for %.dtb targets

[Rob Herring]

While not documented, schema checks for single dtb targets mostly work
already by setting 'CHECK_DTBS=1'. However, the dependencies are not
handled and it only works if 'make dt_bindings_check' was run first and
generated processed-schema.json. In addition, changing a binding file
doesn't cause the schema to be rebuilt and dtb to be revalidated.

Making this work turns out to be simple. Whenever CHECK_DTBS is set,
make 'dt_binding_check' a 'dtbs_prepare' dependency.

I reimplemented here what Masahiro had originally come up with a while
back.

Cc: Marek Vasut <marex@xxxxxxx>
Cc: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
---
 Makefile | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 6aa709df6bde..a99d5c4de0fc 100644
--- a/Makefile
+++ b/Makefile
@@ -1467,7 +1467,10 @@ dtbs_prepare: include/config/kernel.release scripts_dtc
 
 ifneq ($(filter dtbs_check, $(MAKECMDGOALS)),)
 export CHECK_DTBS=y
-dtbs: dt_binding_check
+endif
+
+ifneq ($(CHECK_DTBS),)
+dtbs_prepare: dt_binding_check
 endif
 
 dtbs_check: dtbs
-- 
2.35.1