[RFC PATCH 3/3] scripts: Use -B dtc option to generate dtb build information.

[Alexandre Torgue]

This commit adds a new script to create a string in tmp file with
some information (date, linux version, user). This file is then used by
dtc with -B option to append dts file with a new property.
During kernel boot it will then be possible to printout DTB build
information (date, linux version used, user).

Signed-off-by: Alexandre Torgue <alexandre.torgue@xxxxxx>

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 3fa32f83b2d7..6a98eac1e56d 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -235,6 +235,7 @@ quiet_cmd_gzip = GZIP    $@
 # DTC
 # ---------------------------------------------------------------------------
 DTC ?= $(objtree)/scripts/dtc/dtc
+DTB_GEN_INFO ?= $(objtree)/scripts/gen_dtb_build_info
 
 # Disable noisy checks by default
 ifeq ($(findstring 1,$(KBUILD_EXTRA_WARN)),)
@@ -275,11 +276,13 @@ $(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 $(2) -o $@ -b 0 \
+       $(DTB_GEN_INFO) $(@).info ;\
+       $(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
+       $(DTC) -O $(2) -o $@ -b 0 -B $(@).info\
 		$(addprefix -i,$(dir $<) $(DTC_INCLUDE)) $(DTC_FLAGS) \
-		-d $(depfile).dtc.tmp $(dtc-tmp) ; \
-	cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)
+               -d $(depfile).dtc.tmp $(dtc-tmp) ; \
+       rm $(@).info ; \
+       cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)
 
 $(obj)/%.dtb: $(src)/%.dts $(DTC) FORCE
 	$(call if_changed_dep,dtc,dtb)
diff --git a/scripts/gen_dtb_build_info b/scripts/gen_dtb_build_info
new file mode 100755
index 000000000000..30cf7506b9d5
--- /dev/null
+++ b/scripts/gen_dtb_build_info
@@ -0,0 +1,11 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+DTB_TARGET=$@
+COMPILE_BY=$(whoami | sed 's/\\/\\\\/')
+
+touch $DTB_TARGET
+
+{
+  echo From Linux $KERNELRELEASE by $COMPILE_BY the $(date).
+} > $DTB_TARGET
-- 
2.17.1