Re: [Buildroot] [PATCH v5 3/3] board/versal2/post-image.sh: add custom hardware support

[Luca Ceresoli via buildroot <buildroot@buildroot.org>]

On Sun Mar 15, 2026 at 4:43 PM CET, Neal Frager wrote:
> Users will ultimately need the BR2_LINUX_KERNEL_CUSTOM_DTS_DIR config to
> import custom dts files for custom versal2 hardware. Improve the post-image.sh
> to support either the default device tree which comes from u-boot or a
> custom device tree for custom hardware.
>
> To keep the example post-image script as simple as possible, it assumes that
> the first DTB in the LINUX_DTBS list is the one for creating the system.dtb
> filename that u-boot will use for booting. Users are free to implement their
> own post-image scripts for use cases with multiple DTBs or overlays.
>
> Signed-off-by: Neal Frager <neal.frager@amd.com>
> ---
> V1->V2:
> - new to patch series
> V2->V5:
> - fixed shellcheck issue
> - merged with zynqmp and versal patch set
> ---
>  board/versal2/post-image.sh | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/board/versal2/post-image.sh b/board/versal2/post-image.sh
> index af50909fb1..3037e0a5ab 100755
> --- a/board/versal2/post-image.sh
> +++ b/board/versal2/post-image.sh
> @@ -1,9 +1,17 @@
>  #!/bin/sh
>
> -# By default U-Boot loads DTB from a file named "system.dtb", and
> -# with versal2, the Linux DTB is the same as the U-Boot DTB, so
> -# let's use a symlink since the DTB is the same.
> -ln -fs "u-boot.dtb" "${BINARIES_DIR}/system.dtb"
> +# By default U-Boot loads DTB from a file named "system.dtb".
> +# With versal2, there is no default dts in the Linux kernel tree
> +# because the default is the same as the u-boot.dtb. This means
> +# it is necessary to cover two cases, a custom dts or the default.
> +# The BR2_LINUX_KERNEL_DTS_SUPPORT will only be set for custom dts
> +# files

Out of my ignorance, is this assumption always correct? What if the main
dtb comes from u-boot but the kernel package is used to build some overlays
(and no dtb)? This patch would break such configs, because is would link
system.dtb to some dtbo instead of u-boot.dtb.

Is this a valid use case in the first place?

> , so it can be used for checking which case is configured.
> +if grep -Eq "^BR2_LINUX_KERNEL_DTS_SUPPORT=y$" "${BR2_CONFIG}"; then
> +	LINUX_DTBS="$(make --no-print-directory VARS=LINUX_DTBS printvars)"
> +	ln -fs "$(basename "${LINUX_DTBS%% *}")" "${BINARIES_DIR}/system.dtb"
> +else
> +	ln -fs "u-boot.dtb" "${BINARIES_DIR}/system.dtb"
> +fi

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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