[PATCH v3 0/3] allow control DTB to double as "FIT image"

[PATCH v3 0/3] allow control DTB to double as "FIT image"

[Rasmus Villemoes]

The commit message for patch 1 explains what it is I'd like to be able
to do, but here's some more background:

For a long time, we've embedded the boot script in the U-Boot binary
by building a bootscript.itb, and using a .dtsi like

  / {
          config {
                 bootscript = /incbin/("/path/to/bootscript.itb");
          };
  };

which in turn is mentioned in CONFIG_DEVICE_TREE_INCLUDES, that
bootscript.itb FIT image has been embedded in U-Boot's control
dtb. Running that was then a matter of doing

  fdt addr ${fdtcontroladdr} && fdt get addr bsaddr /config bootscript && source ${bsaddr}

There are a couple of advantage of having the bootscript (and other
script logic) embedded in the U-Boot binary. First, there's no need to
figure out some separate partition to store the script in, and making
sure that gets updated whenever the bootloader itself does. Second,
one doesn't need to worry about verifying the script; whatever steps
one needs to take to implement secure boot for U-Boot itself will by
necessity also cover the control dtb (if nothing else then because
that's where the public key for the kernel verification lives). And
third, the boot script is automatically updated together with U-Boot
itself; and if U-Boot is stored in an eMMC boot partition, that update
is guaranteed to be atomic.

Now with the stricter requirements of libfdt starting from v2026.04,
the above command no longer worked, or only half the time, because the
embedded FIT image may not land on an 8-byte aligned address. So that
line had to be changed a little (line breaks added)

  fdt addr ${fdtcontroladdr}
    && fdt get addr bsaddr /config bootscript
    && fdt get size bssize /config bootscript
    && cp.b ${bsaddr} ${loadaddr} ${bssize}
    && source ${loadaddr}

which is getting quite unwieldy.

Then it struck me that one could perhaps simplify all of this quite a
lot: Cut out the intermediate bootscript.itb, just create a .dtsi
which directly puts a /images node inside the control dtb

/ {
  	images {
		default = "bootscript";
		bootscript {
			description = "Boot script";
			data = /incbin/("/path/to/bootscript.sh");
			type = "script";
			compression = "none";
		};
	};
};

and treat the control dtb itself as a FIT image; so the command to put
in $bootcmd becomes simply

  source ${fdtcontroladdr}:bootscript

and embedding other pieces of callable scripts is quite trivial.

And that almost works out-of-the-box, except for the fit_check_format() sanity check.

Introduce a CONFIG_ knob that allows one to opt out of those sanity
checks, for the special case of the address being checked being
identical to gd->fdt_blob.

v1: https://lore.kernel.org/u-boot/20260512161631.284143-1-ravi@prevas.dk/
v2: https://lore.kernel.org/u-boot/20260519225458.5587-1-ravi@prevas.dk/

Changes in v3:

- Factor out tail of fit_check_format (verifying existence of /images
  node) to separate function, instead of using goto.

- Reword the config help text to emphasize that this is safe to use
  even in a secure boot setup.

- Put test cases in separate function to not lose coverage when
  !CONTROL_DTB_AS_FIT, and add a separate function verifying that
  source ${fdtcontroladdr} is always rejected in that case.

- Change author email address to private address because company smtp
  server (*cough* office365 *cough*) can apparently no longer be used
  for, erh, sending emails ?!

Changes in v2:

- Guard this behind a CONFIG_ option

- Move the exemption logic into fit_check_format()

- Add a section to doc/develop/devicetree/control.rst describing this feature.

- Fix and improve the included tests.

Rasmus Villemoes (3):
  image-fit.c: introduce CONTROL_DTB_AS_FIT config knob
  doc: develop: add section on embedding scripts inside control DTB
  test: hook up test of allowing control DTB to act as FIT image

 arch/sandbox/dts/sandbox-boot.sh      |  2 +
 arch/sandbox/dts/sandbox-inner.sh     |  4 ++
 arch/sandbox/dts/sandbox-outer.sh     |  4 ++
 arch/sandbox/dts/sandbox_scripts.dtsi | 24 +++++++++++
 boot/Kconfig                          | 13 ++++++
 boot/image-fit.c                      | 21 +++++++---
 configs/sandbox_defconfig             |  2 +
 doc/develop/devicetree/control.rst    | 58 +++++++++++++++++++++++++++
 test/py/tests/test_source.py          | 32 +++++++++++++++
 9 files changed, 154 insertions(+), 6 deletions(-)
 create mode 100644 arch/sandbox/dts/sandbox-boot.sh
 create mode 100644 arch/sandbox/dts/sandbox-inner.sh
 create mode 100644 arch/sandbox/dts/sandbox-outer.sh
 create mode 100644 arch/sandbox/dts/sandbox_scripts.dtsi

-- 
2.54.0

[PATCH v3 1/3] image-fit.c: introduce CONTROL_DTB_AS_FIT config knob

[Rasmus Villemoes]

Having scripts embedded one way or the other in the U-Boot binary
means they are automatically verified/trusted by whatever mechanism
verifies U-Boot.

Writing those scripts in the built-in environment leads to
backslatitis and missing or wrong quoting and is generally not very
readable or maintainable.

Maintaining scripts in external files allows one
to have both syntax highlighting and to some extent apply shellcheck
on it (though U-Boot's shell is of course not quite POSIX sh, so some
'#shellcheck disable' directives are needed). Getting those into the
U-Boot binary is then a matter of having a suitable .dtsi file such as

/ {
	images {
		default = "boot";
		boot {
			description = "Bootscript";
			data = /incbin/("boot.sh");
			type = "script";
			compression = "none";
		};
		factory-reset {
			description = "Script for performing factory reset";
			data = /incbin/("factory-reset.sh");
			type = "script";
			compression = "none";
		};
	};
};

and making that part of CONFIG_DEVICE_TREE_INCLUDES, so that U-Boot's
control DTB effectively doubles as a FIT image containing a few
"script" entries. At run-time, one's default bootcommand can then
simply be

  source ${fdtcontroladdr}:boot

Except of course that the control DTB is in fact not quite a FIT
image. The lack of timestamp and description properties could
potentially be worked around (by just adding those via that same
.dtsi), but the no-@ check is not possible to get around. But since
the control dtb is by definition trusted, we can make an exception for
that particular address, if the new CONTROL_DTB_AS_FIT config option
is enabled.

One can of course build an ordinary FIT image with those
scripts. However, that requires extra steps in the boot command for
loading that script from storage, requires one to use "configurations"
for pointing at a single script to run, and signing the FIT image
using the same key used for verifying the kernel. Moreover, in certain
situations, such as bootstrapping/production, there is no place to
load that FIT image from, and it is much simpler to just have the
necessary scripts be part of the U-Boot image itself.

Signed-off-by: Rasmus Villemoes <ravi@prevas.dk>
Signed-off-by: Rasmus Villemoes <rv@rasmusvillemoes.dk>
---
 boot/Kconfig     | 13 +++++++++++++
 boot/image-fit.c | 21 +++++++++++++++------
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/boot/Kconfig b/boot/Kconfig
index ae6f09a6ede..19a170957c6 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -103,6 +103,19 @@ config FIT_FULL_CHECK
 	  of bugs or omissions in the code. This includes a bad structure,
 	  multiple root nodes and the like.
 
+config CONTROL_DTB_AS_FIT
+	bool "Allow U-Boot's control DTB to act as FIT image"
+	help
+	  Enable this to exempt U-Boot's control DTB from the sanity
+	  checks done to ensure FIT images are valid. This can for
+	  example be used to embed whole scripts in the control DTB,
+	  that can then be invoked using 'source ${fdtcontroladdr}'.
+	  In a secure boot setup, this is safe, as the control DTB is
+	  necessarily covered by any mechanism verifying U-Boot and
+	  can therefore be trusted. This only affects the case where
+	  the image being checked is gd->fdt_blob. See
+	  doc/develop/devicetree/control.rst for details.
+
 config FIT_SIGNATURE
 	bool "Enable signature verification of FIT uImages"
 	depends on DM
diff --git a/boot/image-fit.c b/boot/image-fit.c
index b0fcaf6e17f..18498d0b51a 100644
--- a/boot/image-fit.c
+++ b/boot/image-fit.c
@@ -1664,6 +1664,16 @@ static int fdt_check_no_at(const void *fit, int parent)
 	return 0;
 }
 
+static int fit_check_images_node(const void *fit)
+{
+	if (fdt_path_offset(fit, FIT_IMAGES_PATH) < 0) {
+		log_debug("Wrong FIT format: no images parent node\n");
+		return -ENOENT;
+	}
+
+	return 0;
+}
+
 int fit_check_format(const void *fit, ulong size)
 {
 	int ret;
@@ -1676,6 +1686,10 @@ int fit_check_format(const void *fit, ulong size)
 		return -ENOEXEC;
 	}
 
+	/* For the control DTB to act as a FIT image, we only require an /images node. */
+	if (CONFIG_IS_ENABLED(CONTROL_DTB_AS_FIT) && fit == gd_fdt_blob())
+		return fit_check_images_node(fit);
+
 	if (CONFIG_IS_ENABLED(FIT_FULL_CHECK)) {
 		/*
 		 * If we are not given the size, make do with calculating it.
@@ -1724,12 +1738,7 @@ int fit_check_format(const void *fit, ulong size)
 	}
 
 	/* mandatory subimages parent '/images' node */
-	if (fdt_path_offset(fit, FIT_IMAGES_PATH) < 0) {
-		log_debug("Wrong FIT format: no images parent node\n");
-		return -ENOENT;
-	}
-
-	return 0;
+	return fit_check_images_node(fit);
 }
 
 int fit_conf_find_compat(const void *fit, const void *fdt)
-- 
2.54.0

Re: [PATCH v3 1/3] image-fit.c: introduce CONTROL_DTB_AS_FIT config knob

[Simon Glass]

Hi Rasmus,

On 2026-05-29T19:46:18, Rasmus Villemoes <rv@rasmusvillemoes.dk> wrote:
> image-fit.c: introduce CONTROL_DTB_AS_FIT config knob
>
> Having scripts embedded one way or the other in the U-Boot binary
> means they are automatically verified/trusted by whatever mechanism
> verifies U-Boot.
>
> Writing those scripts in the built-in environment leads to
> backslatitis and missing or wrong quoting and is generally not very
> readable or maintainable.
>
> Maintaining scripts in external files allows one
> to have both syntax highlighting and to some extent apply shellcheck
> on it (though U-Boot's shell is of course not quite POSIX sh, so some
> '#shellcheck disable' directives are needed). Getting those into the
> U-Boot binary is then a matter of having a suitable .dtsi file such as
>
> / {
>         images {
>                 default = 'boot';
>                 boot {
> [...]
>
> boot/Kconfig     | 13 +++++++++++++
>  boot/image-fit.c | 21 +++++++++++++++------
>  2 files changed, 28 insertions(+), 6 deletions(-)

> diff --git a/boot/image-fit.c b/boot/image-fit.c
> @@ -1676,6 +1686,10 @@ int fit_check_format(const void *fit, ulong size)
> +     /* For the control DTB to act as a FIT image, we only require an /images node. */
> +     if (CONFIG_IS_ENABLED(CONTROL_DTB_AS_FIT) && fit == gd_fdt_blob())
> +             return fit_check_images_node(fit);

Please wrap this comment to 80 columns

Reviewed-by: Simon Glass <sjg@chromium.org>

Regards,
Simon

[PATCH v3 2/3] doc: develop: add section on embedding scripts inside control DTB

[Rasmus Villemoes]

Add a section that explains how one can embed scripts in the control
DTB and run them from the U-Boot shell, the advantages of doing that
compared to using a separately built FIT image, and the configuration
knob that must be turned on to allow this to work.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Rasmus Villemoes <rv@rasmusvillemoes.dk>
---
 doc/develop/devicetree/control.rst | 58 ++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/doc/develop/devicetree/control.rst b/doc/develop/devicetree/control.rst
index 634114af59a..7d6117d5c4b 100644
--- a/doc/develop/devicetree/control.rst
+++ b/doc/develop/devicetree/control.rst
@@ -232,6 +232,64 @@ outside the U-Boot repository. You can use `DEVICE_TREE_INCLUDES` Kconfig
 option to specify a list of .dtsi files that will also be included when
 building .dtb files.
 
+Scripts embedded in control DTB
+-------------------------------
+
+The `DEVICE_TREE_INCLUDES` option can also be used to make the control
+DTB serve double duty as a FIT image. By including a `scripts.dtsi`
+file containing something like::
+
+  / {
+	images {
+		default = "boot";
+		boot {
+			description = "Bootscript";
+			data = /incbin/("boot.sh");
+			type = "script";
+			compression = "none";
+		};
+		factory-reset {
+			description = "Script for performing factory reset";
+			data = /incbin/("factory-reset.sh");
+			type = "script";
+			compression = "none";
+		};
+	};
+  };
+
+one can call those scripts using the `source` command in the U-Boot shell::
+
+  source ${fdtcontroladdr}:boot
+
+or just ``source ${fdtcontroladdr}`` for invoking the default.
+
+Since one does not need to separately build a "real" FIT image
+containing those scripts, this simplifies both the build process and
+the boot logic, as the latter does not need to first load the FIT
+image from storage.
+
+Another advantage is that when the bootloader and boot script must be
+updated together, it is easier to achieve a guaranteed atomic update
+when the boot script is embedded inside the U-Boot binary, instead of
+stored separately.
+
+For the above to work, one must enable the `CONTROL_DTB_AS_FIT` config
+option, which will (when the address passed to the `source` command is
+the address of U-Boot's control DTB) elide certain sanity checks that
+are normally done: With the above `.dtsi` snippet, the control DTB
+does not quite become a "real" FIT image - it lacks `timestamp` and
+`description` properties, but more importantly, FIT images cannot
+contain nodes with `@` in their names (unit addresses) anywhere, and
+the control DTB obviously does have such nodes.
+
+This is not a security problem, as the control DTB is necessarily
+trusted. In any secure boot setup where the bootloader is verified,
+that mechanism must also include verification of the control DTB. So
+in fact, since the scripts embedded this way are then also
+automatically verified, it simplifies implementation of secure
+boot. When using a separate FIT image, one must build it with
+appropriate signatures, just as when building a FIT image containing a
+kernel/dtb/initramfs.
 
 Devicetree bindings schema checks
 ---------------------------------
-- 
2.54.0

[PATCH v3 3/3] test: hook up test of allowing control DTB to act as FIT image

[Rasmus Villemoes]

Add a test demonstrating how one can embed various scripts in the
control DTB.

Verify that the source command can be used with ${fdtcontroladdr} by
itself (invoking the default script), and with :<node-name>
suffix. Check that the scripts themselves can invoke "sibling"
scripts. Also verify that without CONTROL_DTB_AS_FIT set, the control
DTB is not accepted by the source command.

Signed-off-by: Rasmus Villemoes <rv@rasmusvillemoes.dk>
---
 arch/sandbox/dts/sandbox-boot.sh      |  2 ++
 arch/sandbox/dts/sandbox-inner.sh     |  4 ++++
 arch/sandbox/dts/sandbox-outer.sh     |  4 ++++
 arch/sandbox/dts/sandbox_scripts.dtsi | 24 ++++++++++++++++++++
 configs/sandbox_defconfig             |  2 ++
 test/py/tests/test_source.py          | 32 +++++++++++++++++++++++++++
 6 files changed, 68 insertions(+)
 create mode 100644 arch/sandbox/dts/sandbox-boot.sh
 create mode 100644 arch/sandbox/dts/sandbox-inner.sh
 create mode 100644 arch/sandbox/dts/sandbox-outer.sh
 create mode 100644 arch/sandbox/dts/sandbox_scripts.dtsi

diff --git a/arch/sandbox/dts/sandbox-boot.sh b/arch/sandbox/dts/sandbox-boot.sh
new file mode 100644
index 00000000000..4f7fa661151
--- /dev/null
+++ b/arch/sandbox/dts/sandbox-boot.sh
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+echo "* default script"
diff --git a/arch/sandbox/dts/sandbox-inner.sh b/arch/sandbox/dts/sandbox-inner.sh
new file mode 100644
index 00000000000..b8fc8f7484b
--- /dev/null
+++ b/arch/sandbox/dts/sandbox-inner.sh
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+
+# Some comment.
+echo "* inner"
diff --git a/arch/sandbox/dts/sandbox-outer.sh b/arch/sandbox/dts/sandbox-outer.sh
new file mode 100644
index 00000000000..40294085433
--- /dev/null
+++ b/arch/sandbox/dts/sandbox-outer.sh
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+echo "* outer 1"
+source ${fdtcontroladdr}:inner
+echo "* outer 2"
diff --git a/arch/sandbox/dts/sandbox_scripts.dtsi b/arch/sandbox/dts/sandbox_scripts.dtsi
new file mode 100644
index 00000000000..c800ec39e87
--- /dev/null
+++ b/arch/sandbox/dts/sandbox_scripts.dtsi
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+/ {
+	images {
+		default = "boot";
+		boot {
+			description = "Test boot script";
+			data = /incbin/("sandbox-boot.sh");
+			type = "script";
+			compression = "none";
+		};
+		outer {
+			description = "Script testing recursion";
+			data = /incbin/("sandbox-outer.sh");
+			type = "script";
+			compression = "none";
+		};
+		inner {
+			description = "Another test script";
+			data = /incbin/("sandbox-inner.sh");
+			type = "script";
+			compression = "none";
+		};
+	};
+};
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index ba800f7d19d..bfdc5ee6010 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -20,6 +20,7 @@ CONFIG_EFI_CAPSULE_AUTHENTICATE=y
 CONFIG_EFI_CAPSULE_CRT_FILE="board/sandbox/capsule_pub_key_good.crt"
 CONFIG_BUTTON_CMD=y
 CONFIG_FIT=y
+CONFIG_CONTROL_DTB_AS_FIT=y
 CONFIG_FIT_SIGNATURE=y
 CONFIG_FIT_CIPHER=y
 CONFIG_FIT_VERBOSE=y
@@ -152,6 +153,7 @@ CONFIG_CMD_STACKPROTECTOR_TEST=y
 CONFIG_CMD_SPAWN=y
 CONFIG_MAC_PARTITION=y
 CONFIG_OF_LIVE=y
+CONFIG_DEVICE_TREE_INCLUDES="sandbox_scripts.dtsi"
 CONFIG_ENV_IS_NOWHERE=y
 CONFIG_ENV_IS_IN_FAT=y
 CONFIG_ENV_IS_IN_EXT4=y
diff --git a/test/py/tests/test_source.py b/test/py/tests/test_source.py
index 970d8c79869..f453e9be1a9 100644
--- a/test/py/tests/test_source.py
+++ b/test/py/tests/test_source.py
@@ -34,3 +34,35 @@ def test_source(ubman):
     ubman.run_command('fdt rm /images default')
     assert 'Fail' in ubman.run_command('source || echo Fail')
     assert 'Fail' in ubman.run_command('source \\# || echo Fail')
+
+@pytest.mark.boardspec('sandbox')
+@pytest.mark.buildconfigspec('cmd_echo')
+@pytest.mark.buildconfigspec('cmd_source')
+@pytest.mark.buildconfigspec('fit')
+@pytest.mark.buildconfigspec('control_dtb_as_fit')
+def test_source_control_dtb(ubman):
+    output = ubman.run_command('source ${fdtcontroladdr}')
+    assert '* default script' in output
+
+    output = ubman.run_command('source ${fdtcontroladdr}:boot')
+    assert '* default script' in output
+
+    output = ubman.run_command('source ${fdtcontroladdr}:outer')
+    assert '* outer 1' in output
+    assert '* inner' in output
+    assert '* outer 2' in output
+
+    output = ubman.run_command('source ${fdtcontroladdr}:inner')
+    assert '* outer' not in output
+    assert '* inner' in output
+
+    assert 'Fail' in ubman.run_command('source ${fdtcontroladdr}:no-such-script || echo Fail')
+
+@pytest.mark.boardspec('sandbox')
+@pytest.mark.buildconfigspec('cmd_echo')
+@pytest.mark.buildconfigspec('cmd_source')
+@pytest.mark.buildconfigspec('fit')
+@pytest.mark.notbuildconfigspec('control_dtb_as_fit')
+def test_source_reject_control_dtb(ubman):
+    assert 'Fail' in ubman.run_command('source ${fdtcontroladdr} || echo Fail')
+    assert 'Fail' in ubman.run_command('source ${fdtcontroladdr}:boot || echo Fail')
-- 
2.54.0

Re: [PATCH v3 3/3] test: hook up test of allowing control DTB to act as FIT image

[Simon Glass]

Hi Rasmus,

On 2026-05-29T19:46:18, Rasmus Villemoes <rv@rasmusvillemoes.dk> wrote:
> test: hook up test of allowing control DTB to act as FIT image
>
> Add a test demonstrating how one can embed various scripts in the
> control DTB.
>
> Verify that the source command can be used with ${fdtcontroladdr} by
> itself (invoking the default script), and with :<node-name>
> suffix. Check that the scripts themselves can invoke 'sibling'
> scripts. Also verify that without CONTROL_DTB_AS_FIT set, the control
> DTB is not accepted by the source command.
>
> Signed-off-by: Rasmus Villemoes <rv@rasmusvillemoes.dk>
>
> arch/sandbox/dts/sandbox-boot.sh      |  2 ++
>  arch/sandbox/dts/sandbox-inner.sh     |  4 ++++
>  arch/sandbox/dts/sandbox-outer.sh     |  4 ++++
>  arch/sandbox/dts/sandbox_scripts.dtsi | 24 ++++++++++++++++++++++++
>  configs/sandbox_defconfig             |  2 ++
>  test/py/tests/test_source.py          | 32 ++++++++++++++++++++++++++++++++
>  6 files changed, 68 insertions(+)

> diff --git a/test/py/tests/test_source.py b/test/py/tests/test_source.py
> @@ -34,3 +34,35 @@ def test_source(ubman):
> +@pytest.mark.boardspec('sandbox')
> +@pytest.mark.buildconfigspec('cmd_echo')
> +@pytest.mark.buildconfigspec('cmd_source')
> +@pytest.mark.buildconfigspec('fit')
> +@pytest.mark.notbuildconfigspec('control_dtb_as_fit')
> +def test_source_reject_control_dtb(ubman):
> +    assert 'Fail' in ubman.run_command('source ${fdtcontroladdr} || echo Fail')
> +    assert 'Fail' in ubman.run_command('source ${fdtcontroladdr}:boot || echo Fail')

Just to check: since sandbox_defconfig now enables CONTROL_DTB_AS_FIT,
this case is skipped on the main sandbox build. Did you confirm it
runs on one of the other variants (sandbox_noinst / sandbox_spl /
sandbox64)? If none satisfy the marker combination, this is dead code.
Perhaps note in the commit message where it does run?

Reviewed-by: Simon Glass <sjg@chromium.org>

Regards,
Simon

Re: [PATCH v3 3/3] test: hook up test of allowing control DTB to act as FIT image

[Rasmus Villemoes]

On Fri, May 29 2026, "Simon Glass" <sjg@chromium.org> wrote:

> Hi Rasmus,
>
> On 2026-05-29T19:46:18, Rasmus Villemoes <rv@rasmusvillemoes.dk> wrote:
>> test: hook up test of allowing control DTB to act as FIT image
>>
>> Add a test demonstrating how one can embed various scripts in the
>> control DTB.
>>
>> Verify that the source command can be used with ${fdtcontroladdr} by
>> itself (invoking the default script), and with :<node-name>
>> suffix. Check that the scripts themselves can invoke 'sibling'
>> scripts. Also verify that without CONTROL_DTB_AS_FIT set, the control
>> DTB is not accepted by the source command.
>>
>> Signed-off-by: Rasmus Villemoes <rv@rasmusvillemoes.dk>
>>
>> arch/sandbox/dts/sandbox-boot.sh      |  2 ++
>>  arch/sandbox/dts/sandbox-inner.sh     |  4 ++++
>>  arch/sandbox/dts/sandbox-outer.sh     |  4 ++++
>>  arch/sandbox/dts/sandbox_scripts.dtsi | 24 ++++++++++++++++++++++++
>>  configs/sandbox_defconfig             |  2 ++
>>  test/py/tests/test_source.py          | 32 ++++++++++++++++++++++++++++++++
>>  6 files changed, 68 insertions(+)
>
>> diff --git a/test/py/tests/test_source.py b/test/py/tests/test_source.py
>> @@ -34,3 +34,35 @@ def test_source(ubman):
>> +@pytest.mark.boardspec('sandbox')
>> +@pytest.mark.buildconfigspec('cmd_echo')
>> +@pytest.mark.buildconfigspec('cmd_source')
>> +@pytest.mark.buildconfigspec('fit')
>> +@pytest.mark.notbuildconfigspec('control_dtb_as_fit')
>> +def test_source_reject_control_dtb(ubman):
>> +    assert 'Fail' in ubman.run_command('source ${fdtcontroladdr} || echo Fail')
>> +    assert 'Fail' in ubman.run_command('source ${fdtcontroladdr}:boot || echo Fail')
>
> Just to check: since sandbox_defconfig now enables CONTROL_DTB_AS_FIT,
> this case is skipped on the main sandbox build. Did you confirm it
> runs on one of the other variants (sandbox_noinst / sandbox_spl /
> sandbox64)? If none satisfy the marker combination, this is dead code.

Indeed, I didn't really know exactly what boardspec('sandbox') meant,
and couldn't find any documentation on it, so I kinda assumed it meant
"all the sandbox_*" defconfigs.

But regardless, I suppose the right thing to do is to just drop that
boardspec line, since this really should fail on any .config without
control_dtb_as_fit, regardless of whether any scripts are included in
the .dtb via an appropriate .dtsi or not.

Rasmus