[U-Boot] [PATCH v4 011/100] fdt: Show the preprocessed .dts file on error

Simon Glass sjg at chromium.org
Fri Nov 22 04:17:36 UTC 2019

When device-tree compilation fails it is sometimes tricky to see which
line is broken, since the input file to dtc is a pre-processed version
of the device tree.

Add a line that points to the file that needs to be checked:

When the error is in the main .dts file, output is something like this:

   output: 'Error: arch/x86/dts/.chromebook_coral.dtb.pre.tmp:478.46-47
	syntax error
   FATAL ERROR: Unable to parse input tree

but in fact looking at that file shows nothing useful:


Instead we need to look at the preprocessed file, which shows:

   163 ((1U << 30) | (1 << 10)) ((0xb << 10) | PAD_CFG1_IOSSTATE_HIZCRX1)

Here it is clear that PAD_CFG1_IOSSTATE_HIZCRX1 is not defined and so is
not being resolved by the preprocessor.

This commit adds an additional useful message:

   Check arch/x86/dts/.chromebook_coral.dtb.dts.tmp for errors

Note that if the error is reported in an included file, such as
u-boot.dtsi then the output is the following:

   Error: arch/x86/dts/u-boot.dtsi:137.14-15 syntax error
   FATAL ERROR: Unable to parse input tree

But again, if the error is due to a preprocessor failure, like this:

   filename = CONFIG_IFW_INPUT_FILE;

then you can't tell what the problem is by looking at the source. All you
see is the original code:

	intel-ifwi {
	intel-fsp-m {
		filename = CONFIG_FSP_FILE_M;

Everything looks fine. But looking at the output of the preprocessor:

 intel-ifwi {
 intel-fsp-m {
  filename = "fsp_m.bin";

This shows that the filename (normally "fitimage.bin") has not been
inserted the preprocess, leading to the realisation that the value should

If the above does not make sense, I encourage people to try introducing
errors in the device tree preprocessed values.

Signed-off-by: Simon Glass <sjg at chromium.org>

Changes in v4:
- One last desperate attempt to try to explain the purpose of this commit
- Update the message to mention the preprocessed file, not un-preprocessed

Changes in v3:
- Update example error message to better show the intended purpose

Changes in v2: None

 scripts/Makefile.lib | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index ef116e0e0a..c10cd83a0a 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -300,7 +300,9 @@ cmd_dtc = mkdir -p $(dir ${dtc-tmp}) ; \
 	$(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $(pre-tmp) ; \
 	$(DTC) -O dtb -o $@ -b 0 \
 		-i $(dir $<) $(DTC_FLAGS) \
-		-d $(depfile).dtc.tmp $(dtc-tmp) ; \
+		-d $(depfile).dtc.tmp $(dtc-tmp) || \
+		(echo "Check $(shell pwd)/$(pre-tmp) for errors" && false) \
+		; \
 	cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile) ; \
 	sed -i "s:$(pre-tmp):$(<):" $(depfile)

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