* Re: [PATCH] kbuild: fix compilation of dtb specified on command-line without make rule
[not found] <20251120140645.478623-1-thomas.de_schampheleire@nokia.com>
@ 2025-11-21 6:42 ` Nathan Chancellor
2025-11-21 19:46 ` Nicolas Schier
0 siblings, 1 reply; 2+ messages in thread
From: Nathan Chancellor @ 2025-11-21 6:42 UTC (permalink / raw)
To: Thomas De Schampheleire
Cc: linux-kbuild, Masahiro Yamada, Nicolas Schier, linux-kernel,
devicetree, Rob Herring
+ Rob, as he reviewed e7e2941300d2
On Thu, Nov 20, 2025 at 03:06:43PM +0100, Thomas De Schampheleire wrote:
> Since commit e7e2941300d2 ("kbuild: split device tree build rules into
> scripts/Makefile.dtbs"), it is no longer possible to compile a device tree
> blob that is not specified in a make rule
> like:
> dtb-$(CONFIG_FOO) += foo.dtb
>
> Before the mentioned commit, one could copy a dts file to e.g.
> arch/arm64/boot/dts/ (or a new subdirectory) and then convert it to a dtb
> file using:
> make ARCH=arm64 foo.dtb
>
> In this scenario, both 'dtb-y' and 'dtb-' are empty, and the inclusion of
> scripts/Makefile.dtbs relies on 'targets' to contain the MAKECMDGOALS. The
> value of 'targets', however, is only final later in the code.
>
> Move the conditional include of scripts/Makefile.dtbs down to where the
> value of 'targets' is final.
>
> Fixes: e7e2941300d2 ("kbuild: split device tree build rules into scripts/Makefile.dtbs")
> Signed-off-by: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
Huh, TIL that .c and .S files can be built in the same way...
$ touch init/foo.c init/bar.S
$ make init/foo.o init/bar.o
$ ls init/.foo.o.cmd init/.bar.o.cmd
init/.bar.o.cmd
init/.foo.o.cmd
I do not necessarily love splitting up the conditional includes from
each other but I am not sure it can be avoided... Nicolas, are you okay
with me taking this as a fix or do you want to take it via kbuild-next?
If the latter:
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> ---
> scripts/Makefile.build | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index d0ee33a487be..6e0f9e922c68 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -527,10 +527,6 @@ ifneq ($(userprogs),)
> include $(srctree)/scripts/Makefile.userprogs
> endif
>
> -ifneq ($(need-dtbslist)$(dtb-y)$(dtb-)$(filter %.dtb %.dtb.o %.dtbo.o,$(targets)),)
> -include $(srctree)/scripts/Makefile.dtbs
> -endif
> -
> # Build
> # ---------------------------------------------------------------------------
>
> @@ -568,6 +564,11 @@ FORCE:
> targets += $(filter-out $(single-subdir-goals), $(MAKECMDGOALS))
> targets := $(filter-out $(PHONY), $(targets))
>
> +# Now that targets is fully known, include dtb rules if needed
> +ifneq ($(need-dtbslist)$(dtb-y)$(dtb-)$(filter %.dtb %.dtb.o %.dtbo.o,$(targets)),)
> +include $(srctree)/scripts/Makefile.dtbs
> +endif
> +
> # Read all saved command lines and dependencies for the $(targets) we
> # may be building above, using $(if_changed{,_dep}). As an
> # optimization, we don't need to read them if the target does not
>
> base-commit: deab487e0f9b39ae4603e22d7d00908ebfc9753c
> --
> 2.51.0
>
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