[Buildroot] [PATCH v5 1/3] board/zynqmp/post-image.sh: add custom hardware support

[Buildroot] [PATCH v5 1/3] board/zynqmp/post-image.sh: add custom hardware support

[Neal Frager via buildroot]

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"
 
 BOARD_DIR="$(dirname "$0")"
 
-- 
2.25.1

_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

[Buildroot] [PATCH v5 2/3] board/versal/post-image.sh: add custom hardware support

[Neal Frager via buildroot]

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 versal evaluation board
to a versal 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/versal/post-image.sh | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/board/versal/post-image.sh b/board/versal/post-image.sh
index 3242e4384a..4a810ff15b 100755
--- a/board/versal/post-image.sh
+++ b/board/versal/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"
 
 BOARD_DIR="$(dirname "$0")"
 
-- 
2.25.1

_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

Re: [Buildroot] [PATCH v5 2/3] board/versal/post-image.sh: add custom hardware support

[Luca Ceresoli via buildroot]

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 versal evaluation board
> to a versal 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>

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

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

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

[Neal Frager via buildroot]

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" "${BINARIES_DIR}/system.dtb"
+# By default U-Boot loads DTB from a file named "system.dtb".
+# With versal2, there is no default dts in the Linux kernel tree
+# because the default is the same as the u-boot.dtb. This means
+# it is necessary to cover two cases, a custom dts or the default.
+# The BR2_LINUX_KERNEL_DTS_SUPPORT will only be set for custom dts
+# files, so it can be used for checking which case is configured.
+if grep -Eq "^BR2_LINUX_KERNEL_DTS_SUPPORT=y$" "${BR2_CONFIG}"; then
+	LINUX_DTBS="$(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
 
 BOARD_DIR="$(dirname "$0")"
 
-- 
2.25.1

_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

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

[Luca Ceresoli via buildroot]

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
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

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

[Frager, Neal via buildroot]

[AMD Official Use Only - AMD Internal Distribution Only]

Hi Luca,

> 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?

Yes, I didn't think of this use case.

My goal was to try to keep the script as simple as possible, so I was only
trying to cover the case where someone migrates from the vek385 to a custom
versal2 board where the device tree is different, and not just an overlay on
top of the vek385 base dtb which is included with u-boot.  Or an overlay on
top of a custom u-boot.dtb.

In the end, this comes back to the same question for the other patches. Should
we improve the script to handle the full list of LINUX_DTBS? In other words,
we would assume that we would want to combine any dtbos and create a
system.dtb that contains everything in the LINUX_DTBS list, including the
original u-boot.dtb in case there are no dtbs in LINUX_DTBS?

It would make the script more complex, so is it worth it?

> , 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

Best regards,
Neal Frager
AMD
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

Re: [Buildroot] [PATCH v5 1/3] board/zynqmp/post-image.sh: add custom hardware support

[Luca Ceresoli via buildroot]

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
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot