Re: [Buildroot] [PATCH v5 1/3] board/zynqmp/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:
> By switching to the LINUX_DTBS variable, the post-image.sh script can now
> work regardless of whether a user is using BR2_LINUX_KERNEL_INTREE_DTS_NAME
> or the BR2_LINUX_KERNEL_CUSTOM_DTS_DIR for custom hardware. This simplifies
> the transition users will make when migrating from a zynqmp evaluation board
> to a zynqmp custom platform.
>
> 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.
>
> Signed-off-by: Neal Frager <neal.frager@amd.com>
> ---
> V1->V2:
> - removed unnecessary $BINARIES_DIR from symlink source
> V2->V3:
> - ignore anything after the first space char of LINUX_DTBS
> V3->V4:
> - use make print-vars to get LINUX_DTBS variable
> V4->V5:
> - fixed shellcheck issue
> ---
>  board/zynqmp/post-image.sh | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/board/zynqmp/post-image.sh b/board/zynqmp/post-image.sh
> index f44b66342d..67b0be65b7 100755
> --- a/board/zynqmp/post-image.sh
> +++ b/board/zynqmp/post-image.sh
> @@ -2,13 +2,9 @@
>
>  # By default U-Boot loads DTB from a file named "system.dtb", so
>  # let's use a symlink with that name that points to the *first*
> -# devicetree listed in the config.
> -
> -FIRST_DT=$(sed -nr \
> -               -e 's|^BR2_LINUX_KERNEL_INTREE_DTS_NAME="(xilinx/)?([-_/[:alnum:]\\.]*).*"$|\2|p' \
> -               "${BR2_CONFIG}")
> -
> -[ -z "${FIRST_DT}" ] || ln -fs "${FIRST_DT}.dtb" "${BINARIES_DIR}/system.dtb"
> +# devicetree in the LINUX_DTBS list.
> +LINUX_DTBS="$(make --no-print-directory VARS=LINUX_DTBS printvars)"
> +ln -fs "$(basename "${LINUX_DTBS%% *}")" "${BINARIES_DIR}/system.dtb"

The whitespace-based string mangling still feels a bit fragile to me, but
it should be OK in the practice as I don't think we support paths with
spaces.

Also there was a concern about what happens in case the first file is a
dtbo, but the old code does not support it either so this patch is not
breaking anything. dtbo-first-in-the-list support can be added later with
more sophisticated scripting if needed.

Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

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