linux-kernel - Re: [PATCH] kbuild: add dtbs

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Message-ID: <Ytp4PyBcCfRsVaG5@bergen.fjasle.eu>
Date:   Fri, 22 Jul 2022 12:13:19 +0200
From:   Nicolas Schier <nicolas@...sle.eu>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, devicetree@...r.kernel.org,
        Rob Herring <robh@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kbuild: add dtbs_prepare target

On Sat, 16 Jul 2022 18:31:22 +0900 Masahiro Yamada wrote:
> Factor out the common prerequisites for DT compilation into the new
> target, dtbs_prepare.
> 
> Add comments in case you wonder why include/config/kernel.release is
> the prerequisite. Our policy is that installation targets must not
> (re)compile any build artifacts in the tree. If we make modules_install
> depend on include/config/kernel.release and it is executed under the
> root privilege, it may be owned by root.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
> 
>  Makefile | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index a9bd55edb75e..8aa4dbb8f878 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1367,16 +1367,22 @@ endif
>  
>  ifneq ($(dtstree),)
>  
> -%.dtb: include/config/kernel.release scripts_dtc
> +%.dtb: dtbs_prepare
>  	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
>  
> -%.dtbo: include/config/kernel.release scripts_dtc
> +%.dtbo: dtbs_prepare
>  	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@

Is there a reason, why both rules are not unified?  I guess it is, but 
I can't see it.

>  
> -PHONY += dtbs dtbs_install dtbs_check
> -dtbs: include/config/kernel.release scripts_dtc
> +PHONY += dtbs dtbs_prepare dtbs_install dtbs_check
> +dtbs: dtbs_prepare
>  	$(Q)$(MAKE) $(build)=$(dtstree)
>  
> +# include/config/kernel.release is not actually required for building DTBs,
> +# but for installing DTBs because INSTALL_DTBS_PATH contains $(KERNELRELEASE).
> +# We do not want to move it to dtbs_install. The policy is installation
> +# targets (, which may run as root) must not modify the tree.

Is the comma after the opening parenthesis intended?

Kind regards,
Nicolas

> +dtbs_prepare: include/config/kernel.release scripts_dtc
> +
>  ifneq ($(filter dtbs_check, $(MAKECMDGOALS)),)
>  export CHECK_DTBS=y
>  dtbs: dt_binding_check
> -- 
> 2.34.1