[RFC][PATCH] kbuild: Produce diff between base DT and U-Boot augmented DT if DEVICE_TREE_DEBUG=1

[Marek Vasut]

On 11/7/25 10:12 AM, Heinrich Schuchardt wrote:
> On 11/6/25 22:08, Marek Vasut wrote:
>> In case DEVICE_TREE_DEBUG is set, produce a diff between the base DT and
>> DT with U-Boot extras, to show how much does the U-Boot DT differ from
>> the base DT. This is particularly useful together with OF_UPSTREAM, to
>> minimize the diff between upstream DTs and U-Boot DTs.
>>
>> Example usage:
>> $ make r8a779g3_sparrowhawk_defconfig && make DEVICE_TREE_DEBUG=1
>> $ cat ./dts/upstream/src/arm64/renesas/r8a779g3-sparrow-hawk.dtb.diff
>>
>> This still has a downside. Even 'dtc -I dts -O dts ...' applied on
>> base DT and U-Boot augmented DT can produce different phandle IDs
>> for the same node in those two DTs, which results in a lot of noise
>> in the resulting diff. The only way I can think of is to patch DTC
>> to emit full paths in those phandles instead, something like a
>> phandle = <&{/full/path/to/remote/end} ...>;

What bothers me is ^ this part.

Hello Heinrich,

> Without documentation developers will not know about the new feature. 
> Could you, please, add a doc/build/ change in the next iteration.
Sure, although I am not convinced it should go in in its current form. 
Please see my first line of comment.