[PATCH v2] Makefile: Fix include directory for OF_UPSTREAM

[Marek Vasut]

On 6/3/24 5:07 PM, Patrick Barsanti wrote:
> Always prioritizing u-boot includes causes problems when trying to migrate
> boards to OF_UPSTREAM that have different local devicetree files with
> respect to the upstream ones, if local DT headers are not dropped.
> At the same time if local and upstream files are the same, migrations
> can be, and have been, introduced without dropping local DT headers.
> This also causes problems whenever upstream DTS and DT headers are patched.
> 
> For example, now migrating a board based on `imx6ul.dtsi` to OF_UPSTREAM
> breaks it, as there are some missing defines in a local DT header file
> (`imx6ul-clock.h`); the solution would be to drop it, which has not always
> been done in previous OF_UPSTREAM migration patches for other boards
> because most of the time the two are the same. This solution is also
> vulnerable to ABI breakage, although this has not yet happened since the
> introduction of OF_UPSTREAM support and is unlikely.
> 
> Maintainers assure backwards compatibility for DT headers when syncing the
> upstream folder with the kernel.

... upstream directory ...

> The problem is that, at the current state, all boards that have not dropped
> their local headers when migrating to OF_UPSTREAM will break once the
> upstream devicetrees are patched, for example, to use any newly added
> define which is not present in the local DT header file, even if those
> changes are backwards compatible.

Why not simply remove the headers ?

Add a WARNING if there are local duplicates .

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