[PATCH v3 0/1] Add support for custom compatible string via optional parameter

[PATCH v3 0/1] Add support for custom compatible string via optional parameter

[Kavinaya S]

This update adds flexibility to FIT image generation by introducing
an optional mechanism to override the DTB compatible string.
Instead of always extracting the value from the DTB, the generator
can now use a custom string defined in build metadata. This is
particularly useful when the FIT configuration requires a different
compatible value than what is embedded in the DTB.

Key changes:
Adds a custom_compatible parameter to fitimage_emit_section_dtb().
Preserves existing behavior when no override is specified.

Usage:
To override the default behavior, define in machine configuration
or local.conf:
FIT_DTB_COMPATIBLE_OVERRIDE:<dtb-filename.dtb> = "custom-compatible-string"

This method avoids using custom ITS files, keeps the build process
consistent, and makes it easy to understand and track changes.

Kavinaya S (1):
  fitimage: Add support for custom compatible string via optional
    parameter

 meta/classes-recipe/kernel-fit-image.bbclass | 3 ++-
 meta/conf/image-fitimage.conf                | 6 ++++++
 meta/lib/oe/fitimage.py                      | 9 ++++++---
 3 files changed, 14 insertions(+), 4 deletions(-)

-- 
2.34.1

[PATCH v3 1/1] fitimage: Add support for custom compatible string via optional parameter

[Kavinaya S]

Currently, fitimage_emit_section_dtb() always reads the 'compatible'
property from the DTB when add_compatible=True. This patch adds an
optional 'custom_compatible' parameter that, when set, overrides the
value from the DTB. If not provided, the existing behavior remains.

The compatible property is also skipped for DTBO nodes.

Suggested-By: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Kavinaya S <kavinaya@qti.qualcomm.com>
---
 meta/classes-recipe/kernel-fit-image.bbclass | 3 ++-
 meta/conf/image-fitimage.conf                | 6 ++++++
 meta/lib/oe/fitimage.py                      | 9 ++++++---
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/meta/classes-recipe/kernel-fit-image.bbclass b/meta/classes-recipe/kernel-fit-image.bbclass
index f04aee1807..2a266242d0 100644
--- a/meta/classes-recipe/kernel-fit-image.bbclass
+++ b/meta/classes-recipe/kernel-fit-image.bbclass
@@ -84,8 +84,9 @@ python do_compile() {
 
             # Copy the dtb or dtbo file into the FIT image assembly directory
             shutil.copyfile(os.path.join(kernel_deploydir, dtb_name), dtb_name)
+            custom_compatible_str = d.getVar(f"FIT_DTB_COMPATIBLE_OVERRIDE:{dtb_name}") or None
             root_node.fitimage_emit_section_dtb(dtb_name, dtb_name,
-                d.getVar("UBOOT_DTB_LOADADDRESS"), d.getVar("UBOOT_DTBO_LOADADDRESS"))
+                d.getVar("UBOOT_DTB_LOADADDRESS"), d.getVar("UBOOT_DTBO_LOADADDRESS"), True, custom_compatible=custom_compatible_str)
 
     if external_kernel_devicetree:
         # iterate over all .dtb and .dtbo files in the external kernel devicetree directory
diff --git a/meta/conf/image-fitimage.conf b/meta/conf/image-fitimage.conf
index 090ee148f4..62f7bcde6c 100644
--- a/meta/conf/image-fitimage.conf
+++ b/meta/conf/image-fitimage.conf
@@ -65,3 +65,9 @@ FIT_ADDRESS_CELLS ?= "1"
 # Machine configurations needing such a script file should include it in the
 # SRC_URI of the kernel recipe and set the FIT_UBOOT_ENV parameter.
 FIT_UBOOT_ENV ?= ""
+
+
+# To override the DTB 'compatible' string in the FIT image, add in your
+# machine.conf or local.conf:
+#
+#  FIT_DTB_COMPATIBLE_OVERRIDE:<dtb-filename.dtb> = "custom-compatible-string"
diff --git a/meta/lib/oe/fitimage.py b/meta/lib/oe/fitimage.py
index f303799155..0d42bca5d7 100644
--- a/meta/lib/oe/fitimage.py
+++ b/meta/lib/oe/fitimage.py
@@ -289,7 +289,7 @@ class ItsNodeRootKernel(ItsNode):
         self._kernel = kernel_node
 
     def fitimage_emit_section_dtb(self, dtb_id, dtb_path, dtb_loadaddress=None,
-                                  dtbo_loadaddress=None, add_compatible=False):
+                                  dtbo_loadaddress=None, add_compatible=False, custom_compatible=None):
         """Emit the fitImage ITS DTB section"""
         load=None
         dtb_ext = os.path.splitext(dtb_path)[1]
@@ -308,8 +308,11 @@ class ItsNodeRootKernel(ItsNode):
 
         # Preserve the DTB's compatible string to be added to the configuration node
         compatible = None
-        if add_compatible:
-            compatible = get_compatible_from_dtb(dtb_path)
+        if add_compatible and dtb_ext != ".dtbo":
+            if custom_compatible:
+                compatible = str(custom_compatible).split()
+            else:
+                compatible = get_compatible_from_dtb(dtb_path)
 
         dtb_node = self.its_add_node_dtb(
             "fdt-" + dtb_id,
-- 
2.34.1

Re: [PATCH v3 1/1] fitimage: Add support for custom compatible string via optional parameter

[Alexander Kanavin]

On Mon, 29 Sept 2025 at 18:12, Kavinaya S <kavinaya@qti.qualcomm.com> wrote:
>
> Currently, fitimage_emit_section_dtb() always reads the 'compatible'
> property from the DTB when add_compatible=True. This patch adds an
> optional 'custom_compatible' parameter that, when set, overrides the
> value from the DTB. If not provided, the existing behavior remains.

At this point you should explain *why* this is necessary. Present your
use case. Explain why the string coming from dtb doesn't work. Don't
be afraid to make the commit message very detailed or very long. The
more details, the more it helps reviewers or people looking at commit
history. I think some of it was previously discussed, and you can
reuse that.

> The compatible property is also skipped for DTBO nodes.

Why?

>  meta/classes-recipe/kernel-fit-image.bbclass | 3 ++-
>  meta/conf/image-fitimage.conf                | 6 ++++++
>  meta/lib/oe/fitimage.py                      | 9 ++++++---

Tests are missing. You will find existing tests in
meta/lib/oeqa/selftest/cases/fitimage.py
Look in particular for test_get_compatible_from_dtb(), and see if you
can extend or copy and tweak that.

> +            custom_compatible_str = d.getVar(f"FIT_DTB_COMPATIBLE_OVERRIDE:{dtb_name}") or None

I suspect you need to use _ here instad of : (but I don't have time to
verify it now).

: is used for bitbake overrides, and this is not one of them.

> +# To override the DTB 'compatible' string in the FIT image, add in your
> +# machine.conf or local.conf:
> +#
> +#  FIT_DTB_COMPATIBLE_OVERRIDE:<dtb-filename.dtb> = "custom-compatible-string"

Add:
# for example,
# <insert an actual working example line>

> diff --git a/meta/lib/oe/fitimage.py b/meta/lib/oe/fitimage.py
> index f303799155..0d42bca5d7 100644
> --- a/meta/lib/oe/fitimage.py
> +++ b/meta/lib/oe/fitimage.py
> @@ -289,7 +289,7 @@ class ItsNodeRootKernel(ItsNode):
>          self._kernel = kernel_node
>
>      def fitimage_emit_section_dtb(self, dtb_id, dtb_path, dtb_loadaddress=None,
> -                                  dtbo_loadaddress=None, add_compatible=False):
> +                                  dtbo_loadaddress=None, add_compatible=False, custom_compatible=None):
>          """Emit the fitImage ITS DTB section"""
>          load=None
>          dtb_ext = os.path.splitext(dtb_path)[1]
> @@ -308,8 +308,11 @@ class ItsNodeRootKernel(ItsNode):
>
>          # Preserve the DTB's compatible string to be added to the configuration node
>          compatible = None
> -        if add_compatible:
> -            compatible = get_compatible_from_dtb(dtb_path)
> +        if add_compatible and dtb_ext != ".dtbo":
> +            if custom_compatible:
> +                compatible = str(custom_compatible).split()
> +            else:
> +                compatible = get_compatible_from_dtb(dtb_path)

get_compatible_from_dtb() is also used in
fitimage_emit_section_dtb_alias(). Does that need to be fixed
similarly?

Alex

Re: [PATCH v3 1/1] fitimage: Add support for custom compatible string via optional parameter

[Kavinaya S]

Hi Alex,

Thanks for the suggestions. I will upload a new patch with the suggestions.

Thanks,
Kavinaya

Re: [OE-core] [PATCH v3 0/1] Add support for custom compatible string via optional parameter

[Ricardo de Araujo (Salveti)]

On Mon, Sep 29, 2025 at 1:12 PM Kavinaya S via lists.openembedded.org
<kavinaya=qti.qualcomm.com@lists.openembedded.org> wrote:
>
> This update adds flexibility to FIT image generation by introducing
> an optional mechanism to override the DTB compatible string.
> Instead of always extracting the value from the DTB, the generator
> can now use a custom string defined in build metadata. This is
> particularly useful when the FIT configuration requires a different
> compatible value than what is embedded in the DTB.

Please provide an example showing how this will be used in your scenario.

Cheers,

Ricardo

Re: [PATCH v3 0/1] Add support for custom compatible string via optional parameter

[Kavinaya S]

Hi Ricardo,

I’ve implemented this change by adding a custom compatible string for one specific DTB in my machine.conf:
FIT_DTB_COMPATIBLE_OVERRIDE:qcs6490-rb3gen2-vision-mezzanine.dtb = "qcom,qcs6490-rb-subtype5"

For qcs6490-rb3gen2.dtb, I have not defined any override, so it continues to use the compatible string extracted from the DTB itself.
As a result, the ITS configuration section looks like this:
configurations {
    default = "conf-qcs6490-rb3gen2.dtb";
    conf-qcs6490-rb3gen2.dtb {
        description = "1 Linux kernel, FDT blob";
        kernel = "kernel-1";
        fdt = "fdt-qcs6490-rb3gen2.dtb";
        compatible = "qcom,qcs6490-rb3gen2", "qcom,qcm6490";
        hash-1 {
            algo = "sha256";
        };
    };

    conf-qcs6490-rb3gen2-vision-mezzanine.dtb {
        description = "0 Linux kernel, FDT blob";
        kernel = "kernel-1";
        fdt = "fdt-qcs6490-rb3gen2-vision-mezzanine.dtb";
        compatible = "qcom,qcs6490-rb-subtype5";
        hash-1 {
            algo = "sha256";
        };
    };
}

This demonstrates how the override works:

If an override is defined in machine.conf, the FIT generator uses that value.
If no override is provided, it falls back to the compatible string from the DTB.

Thanks,
Kavinaya

Re: [PATCH v3 0/1] Add support for custom compatible string via optional parameter

[Dmitry Baryshkov]

On Mon, Sep 29, 2025 at 09:54:38AM -0700, Kavinaya S wrote:
> Hi Ricardo,

Don't delete the whole message you are responding to. How do we know
what are you talking about?

> 
> I’ve implemented this change by adding a custom compatible string for one specific DTB in my machine.conf:
> FIT_DTB_COMPATIBLE_OVERRIDE:qcs6490-rb3gen2-vision-mezzanine.dtb = "qcom,qcs6490-rb-subtype5"

-- 
With best wishes
Dmitry