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

[Tom Rini]

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?

-- 
Tom
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