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Date: Fri, 21 Nov 2025 20:56:59 +0100
From: Nicolas Schier <nsc@kernel.org>
To: "Rob Herring (Arm)" <robh@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>, devicetree@vger.kernel.org,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kbuild: Ensure .dtbo targets are applied to a base .dtb
Message-ID: <aSDEC9D87nZB5RJp@derry.ads.avm.de>
References: <20251114222759.4181152-1-robh@kernel.org>
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In-Reply-To: <20251114222759.4181152-1-robh@kernel.org>

On Fri, Nov 14, 2025 at 04:27:58PM -0600, Rob Herring (Arm) wrote:
> It is a requirement that DT overlays in the kernel are applied at build
> time to a base DTB in order to validate they can be applied and to
> validate them against the DT schemas. DT overlays on their own may be
> incomplete and can't be validated.
> 
> Add a kbuild check so this doesn't have to be checked and fixed
> periodically.
> 
> Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
> ---
>  scripts/Makefile.dtbs | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/scripts/Makefile.dtbs b/scripts/Makefile.dtbs
> index 2d321b813600..15473edc2589 100644
> --- a/scripts/Makefile.dtbs
> +++ b/scripts/Makefile.dtbs
> @@ -10,6 +10,13 @@ real-dtb-y := $(call real-search, $(dtb-y), .dtb, -dtbs)
>  # Base DTB that overlay is applied onto
>  base-dtb-y := $(filter %.dtb, $(call real-search, $(multi-dtb-y), .dtb, -dtbs))
>  
> +# Ensure that any .dtbo is applied to at least one base .dtb. Otherwise, it
> +# does not get validated.
> +applied-dtbo := $(filter %.dtbo, \
> +	$(call real-search, $(call multi-search, $(dtb-y) $(dtb-), .dtb, -dtbs), .dtb, -dtbs))
> +unapplied-dtbo := $(filter-out $(applied-dtbo),$(filter %.dtbo, $(dtb-y)))
> +$(if $(unapplied-dtbo), $(warning .dtbo is not applied to any base: $(unapplied-dtbo)))
> +
>  dtb-y           := $(addprefix $(obj)/, $(dtb-y))
>  multi-dtb-y     := $(addprefix $(obj)/, $(multi-dtb-y))
>  real-dtb-y      := $(addprefix $(obj)/, $(real-dtb-y))
> -- 
> 2.51.0
> 

Acked-by: Nicolas Schier <nsc@kernel.org>

Do you take this via DT tree?

Kind regards,
Nicolas