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

[Marek Vasut]

On 11/7/25 4:56 PM, Tom Rini wrote:
> On Fri, Nov 07, 2025 at 03:06:47PM +0100, Marek Vasut wrote:
>> 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.
> 
> Maybe we put it in the u-boot-extras repo for now as a standalone
> script, so people can be asked to run it and look at the output?
I'd say no, because the output is full of noise unless the phandle 
non-resolution gets somehow improved.