Re: [PATCH v3 2/2] kbuild: Support directory targets for building DTBs

[Rob Herring <robh@kernel.org>]

On Wed, Oct 07, 2026 at 01:39:41PM -0500, Rob Herring (Arm) wrote:
> It is useful to be able to build all the DTBs for a vendor. One can list
> all the .dts files in a directory and convert those to %.dtb targets,
> but that doesn't work for base+overlay DTB targets.
> 
> The 'dtbs' and 'dtbs_check' targets can use the directory rule targets
> as well which avoids different make paths for building DTBs.
> 
> Assisted-by: LLM
> Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
> ---
> v3:
>  - Reworked on top of single target rule for %.dtb
>  - Make dtbs target use directory rule.
>  - Move adding boot/dts subdir out of the arch code. Now supported on
>    every arch (not that useful without vendor dirs).
>  - Removed the need to look at MAKECMDGOALS
>  - Fixed unnecessary rebuilding DT base+overlay targets
>  - Link to v2: https://lore.kernel.org/all/20251120204812.1983452-4-robh@kernel.org/
> 
> v2:
>  - Convert arm, mips and riscv. The other DT enabled arches don't have
>    vendor directories.
>  - Link to v1: https://lore.kernel.org/all/20251113225952.867138-1-robh@kernel.org/
> ---
>  Makefile               | 8 ++++----
>  scripts/Makefile.build | 7 +++++++
>  scripts/Makefile.dtbs  | 2 ++
>  3 files changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index c307ee9293bc..75d290c2b7d8 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1664,8 +1664,8 @@ dtbindingtree := Documentation/devicetree/bindings
>  ifneq ($(dtstree),)
>  
>  PHONY += dtbs dtbs_prepare dtbs_install dtbs_check
> -dtbs: dtbs_prepare
> -	$(Q)$(MAKE) $(build)=$(dtstree) need-dtbslist=1
> +dtbs:
> +	$(Q)$(MAKE) $(dtstree)/
>  
>  # include/config/kernel.release is actually needed when installing DTBs because
>  # INSTALL_DTBS_PATH contains $(KERNELRELEASE). However, we do not want to make
> @@ -2216,7 +2216,7 @@ single-goals := $(addprefix $(build-dir)/, $(single-no-ko))
>  
>  # DT-only targets need host tools, but no architecture-specific preparation.
>  ifneq ($(dtstree),)
> -single-dt-patterns := $(addprefix $(dtstree)/,%.dtb %.dtbo)
> +single-dt-patterns := $(dtstree)/ $(addprefix $(dtstree)/,%.dtb %.dtbo %/)
>  ifeq ($(filter-out $(single-dt-patterns),$(single-no-ko)),)
>  single-build-prep := dtbs_prepare
>  endif
> @@ -2234,7 +2234,7 @@ prepare: outputmakefile
>  # Error messages still appears in the original language
>  PHONY += $(build-dir)
>  $(build-dir): $(single-build-prep)
> -	$(Q)$(MAKE) $(build)=$@ need-builtin=1 need-modorder=1 $(single-goals)
> +	$(Q)$(MAKE) $(build)=$@ need-builtin=1 need-modorder=1 need-dtbslist=1 $(single-goals)

sashiko points out that this creates dtblist files in every directory. 
Will make it conditional on having DTB targets.

Rob