[PATCH v2] kbuild: Support directory targets for building DTBs

[Nathan Chancellor]

On Thu, Nov 20, 2025 at 02:48:13PM -0600, 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.
> 
> Adding the dts subdirectory is straight-forward, but building the
> DTBs should only happen for certain targets (dtbs, dtbs_check, %.dtb,
> %.dtbo, and the directory target(s)).
> 
> The 'scripts_dtc' rule doesn't really depend on 'dt_binding_schemas',
> but the directory target only depends on 'scripts' which depends on
> 'scripts_dtc'.
> 
> Signed-off-by: Rob Herring (Arm) <robh at kernel.org>
> ---
> Please ack and I'll take this in the DT tree.
> 
> I don't really like looking at MAKECMDGOALS, but that's the only way I
> could come up with that works. Maybe someone knows a better way.

Yeah, I do worry that just looking for "dtb" in MAKECMDGOALS could
result in some false positives but in the tree now, I only see one .c
file that would trigger this logic, so maybe it is not that big of a
deal?

  $ fd dtb
  arch/microblaze/boot/dts/linked_dtb.S
  arch/mips/include/asm/mach-loongson64/builtin_dtbs.h
  arch/um/kernel/dtb.c
  drivers/gpu/drm/ci/dtbs-check.sh
  scripts/Makefile.dtbinst
  scripts/Makefile.dtbs

Unfortunately, my Make-fu is pretty weak right now so I do not have any
immediate suggestions but Nicolas might... otherwise, we could probably
ride this for right now and either revert it or forward fix it if
problems come up in further testing, since this does seem rather useful
for folks working on device tree files.

> 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              | 2 +-
>  arch/arm/Kbuild       | 2 ++
>  arch/arm64/Kbuild     | 2 ++
>  arch/mips/Kbuild      | 2 ++
>  arch/riscv/Kbuild     | 2 ++
>  scripts/Makefile.dtbs | 3 +++
>  6 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index 17cfa11ca716..85018d461575 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1494,7 +1494,7 @@ export CHECK_DTBS=y
>  endif
>  
>  ifneq ($(CHECK_DTBS),)
> -dtbs_prepare: dt_binding_schemas
> +scripts_dtc: dt_binding_schemas
>  endif
>  
>  dtbs_check: dtbs
> diff --git a/arch/arm/Kbuild b/arch/arm/Kbuild
> index 69de6b6243c7..af7dd53585c3 100644
> --- a/arch/arm/Kbuild
> +++ b/arch/arm/Kbuild
> @@ -10,5 +10,7 @@ obj-y				+= probes/
>  obj-y				+= net/
>  obj-y				+= crypto/
>  
> +subdir-y += boot/dts
> +
>  # for cleaning
>  subdir- += boot
> diff --git a/arch/arm64/Kbuild b/arch/arm64/Kbuild
> index 5bfbf7d79c99..9e9820af48c9 100644
> --- a/arch/arm64/Kbuild
> +++ b/arch/arm64/Kbuild
> @@ -5,5 +5,7 @@ obj-$(CONFIG_XEN)	+= xen/
>  obj-$(subst m,y,$(CONFIG_HYPERV))	+= hyperv/
>  obj-$(CONFIG_CRYPTO)	+= crypto/
>  
> +subdir-y += boot/dts
> +
>  # for cleaning
>  subdir- += boot
> diff --git a/arch/mips/Kbuild b/arch/mips/Kbuild
> index e901bf554483..6125d00cdcef 100644
> --- a/arch/mips/Kbuild
> +++ b/arch/mips/Kbuild
> @@ -21,5 +21,7 @@ ifdef CONFIG_KVM
>  obj-y += kvm/
>  endif
>  
> +subdir-y += boot/dts
> +
>  # for cleaning
>  subdir- += boot
> diff --git a/arch/riscv/Kbuild b/arch/riscv/Kbuild
> index 126fb738fc44..3cf7f84eb287 100644
> --- a/arch/riscv/Kbuild
> +++ b/arch/riscv/Kbuild
> @@ -7,5 +7,7 @@ obj-$(CONFIG_KVM) += kvm/
>  
>  obj-$(CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY) += purgatory/
>  
> +subdir-y += boot/dts
> +
>  # for cleaning
>  subdir- += boot
> diff --git a/scripts/Makefile.dtbs b/scripts/Makefile.dtbs
> index 2d321b813600..4d0d164df275 100644
> --- a/scripts/Makefile.dtbs
> +++ b/scripts/Makefile.dtbs
> @@ -14,7 +14,10 @@ dtb-y           := $(addprefix $(obj)/, $(dtb-y))
>  multi-dtb-y     := $(addprefix $(obj)/, $(multi-dtb-y))
>  real-dtb-y      := $(addprefix $(obj)/, $(real-dtb-y))
>  
> +ifneq ($(findstring /dts/,$(MAKECMDGOALS))$(findstring dtb,$(MAKECMDGOALS)),)
>  always-y        += $(dtb-y)
> +endif
> +
>  targets         += $(real-dtb-y)
>  
>  # dtbs-list
> -- 
> 2.51.0
>