ref-manual: Document updated UBOOT_CONFIG flow

The UBOOT_CONFIG flow was updated in oe-core [1].  Document all of the
new variables and preferred method of specifying the various controls
for each config.

[1] xxx

Signed-off-by: Ryan Eatmon <reatmon@ti.com>
---
 documentation/ref-manual/classes.rst   |  96 +++++++++++++++++++----
 documentation/ref-manual/variables.rst | 101 +++++++++++++++++++++++--
 2 files changed, 176 insertions(+), 21 deletions(-)

Hi,

On Tue Jan 20, 2026 at 8:21 PM CET, Ryan Eatmon via lists.yoctoproject.org wrote:
> The UBOOT_CONFIG flow was updated in oe-core [1].  Document all of the
> new variables and preferred method of specifying the various controls
> for each config.
>
> [1] xxx
>
> Signed-off-by: Ryan Eatmon <reatmon@ti.com>
> ---
>  documentation/ref-manual/classes.rst   |  96 +++++++++++++++++++----
>  documentation/ref-manual/variables.rst | 101 +++++++++++++++++++++++--
>  2 files changed, 176 insertions(+), 21 deletions(-)
>
> diff --git a/documentation/ref-manual/classes.rst b/documentation/ref-manual/classes.rst
> index 2e219a59c..4eb811387 100644
> --- a/documentation/ref-manual/classes.rst
> +++ b/documentation/ref-manual/classes.rst
> @@ -3269,13 +3269,89 @@ variable using the "type" varflag. Here is an example::
>  The :ref:`ref-classes-uboot-config` class provides support for configuring one
>  or more U-Boot build configurations.
>  
> -There are two ways to configure the recipe for your machine:
> +There are three ways to configure the recipe for your machine:
>  
> --  Using :term:`UBOOT_CONFIG` variable. For example::
> +-  Using the :term:`UBOOT_MACHINE` variable (and its companion variable
> +   :term:`UBOOT_BINARY`). For example::
> +
> +      UBOOT_MACHINE = "config"
> +      UBOOT_BINARY = "u-boot.bin"
> +
> +-  Using :term:`UBOOT_CONFIG` variables. For example::
> +
> +      UBOOT_CONFIG ??= "foo bar"
> +      UBOOT_CONFIG[foo] = "config"
> +      UBOOT_CONFIG[bar] = "config2"
> +
> +      UBOOT_CONFIG_IMAGE_FSTYPES[bar] = "fstype"
> +
> +      UBOOT_CONFIG_BINARY[foo] = "binary"
> +
> +      UBOOT_CONFIG_MAKE_OPTS[foo] = "FOO=1"
> +      UBOOT_CONFIG_MAKE_OPTS[bar] = "BAR=1"
> +
> +      UBOOT_CONFIG_FRAGMENTS[foo] = "foo.fragment"
> +
> +   In this example, all possible configurations are selected (``foo`` and
> +   ``bar``), but it is also possible to build only ``foo`` or ``bar`` by
> +   changing the value of :term:`UBOOT_CONFIG` to include either one or the
> +   other.

For clarity, add:

"""
For example::

   UBOOT_CONFIG = "foo"
"""

> +
> +   Each build configuration is associated to a variable flag definition of
> +   :term:`UBOOT_CONFIG`, and associated changes for each config as defined
> +   in the various UBOOT_CONFIG_* variables.
> +
> +   -  UBOOT_CONFIG[config]: defconfig file selected for this build configuration.

I'm afraid this will render oddly, enclose with `` ``:

"""
-  ``UBOOT_CONFIG[config]``: ...
"""

To keep an hyperlink to the variable definition, I would end each bullet point
in the list here with:

"""
   See the documentation of :term:`UBOOT_CONFIG*` for more information.
"""

> +      These files are found in the source tree's ``configs`` folder of U-Boot.
> +
> +      *This option is mandatory.*
> +
> +   -  :term:`UBOOT_CONFIG_IMAGE_FSTYPES` [config]: image types to append to the
> +      :term:`IMAGE_FSTYPES` variable for image generation for this build
> +      configuration.
> +
> +      This can allow building an extra image format that uses the binary
> +      generated by this build configuration.
> +
> +      This option is not mandatory and can be left unspecified if not needed.
> +
> +   -  :term:`UBOOT_CONFIG_BINARY` [config]: binary to select as the one to deploy in
> +      :term:`DEPLOY_DIR_IMAGE`. The output of a U-Boot build may be more than
> +      one binary, for example::
> +
> +         u-boot.bin
> +         u-boot-with-spl.bin
> +
> +      Setting the ``binary`` value to ``u-boot-with-spl.bin`` will make this
> +      binary the one deployed in :term:`DEPLOY_DIR_IMAGE`. It is renamed to
> +      include the build configuration name in the process (``foo`` or ``bar`` in
> +      the above example).
> +
> +      This option defaults to :term:`UBOOT_BINARY` if not specified.
> +
> +   -  :term:`UBOOT_CONFIG_MAKE_OPTS` [config]: additional options passed to
> +      ``make`` when configuring and compiling U-Boot for this configuration
> +      entry. The options in this entry are added before the options in
> +      :term:`UBOOT_MAKE_OPTS`.
> +
> +      This option is not mandatory and adds nothing if not specified.  If
> +      you do not have a make option for a given config, you can simply not
> +      set the flag for that config.
> +
> +   -  :term:`UBOOT_CONFIG_FRAGMENTS` [config]: additional config fragment(s)
> +      from the source tree that is used during ``do_configure()`` to setup the
> +      build.  The options in this entry are added before the fragments in
> +      :term:`UBOOT_FRAGMENTS`.
> +
> +      This option is not mandatory and adds nothing if not specified.  If
> +      you do not have a fragment a given config, you can simply not set the
> +      flag for that config.
> +
> +-  Or, a legacy method using the :term:`UBOOT_CONFIG` variable by itself. For example::
>  
>        UBOOT_CONFIG ??= "foo bar"
> -      UBOOT_CONFIG[foo] = "config,images,binary,makeopts"
> -      UBOOT_CONFIG[bar] = "config2,images2,binary2,makeopts2"
> +      UBOOT_CONFIG[foo] = "config,images,binary"
> +      UBOOT_CONFIG[bar] = "config2,images2,binary2"
>  
>     In this example, all possible configurations are selected (``foo`` and
>     ``bar``), but it is also possible to build only ``foo`` or ``bar`` by
> @@ -3313,15 +3389,9 @@ There are two ways to configure the recipe for your machine:
>  
>        This option defaults to :term:`UBOOT_BINARY` if unset.
>  
> -   -  ``makeopts``: the additional options passed to ``make`` when configuring
> -      and compiling U-Boot for this configuration entry. The options in this
> -      entry are added before the options in :term:`UBOOT_MAKE_OPTS`.
> -
> --  Or, using the :term:`UBOOT_MACHINE` variable (and its companion variable
> -   :term:`UBOOT_BINARY`). For example::
> -
> -      UBOOT_MACHINE = "config"
> -      UBOOT_BINARY = "u-boot.bin"
> +.. note::

Missing a newline between .. note:: and the text here

> +   It is recommended to not use this legacy flow as any future extensions
> +   to the control knobs will be not added to this methodology.
>  
>  Using :term:`UBOOT_MACHINE` and :term:`UBOOT_CONFIG` at the same time is not
>  possible.
> diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst
> index 4d8a35473..dec260a3f 100644
> --- a/documentation/ref-manual/variables.rst
> +++ b/documentation/ref-manual/variables.rst
> @@ -10669,29 +10669,108 @@ system and gives an overview of their function and contents.
>  
>     :term:`UBOOT_CONFIG`
>        Configures one or more U-Boot configurations to build. Each
> -      configuration can define the :term:`UBOOT_MACHINE` and optionally the
> -      :term:`IMAGE_FSTYPES` and the :term:`UBOOT_BINARY`.
> +      configuration must define the :term:`UBOOT_MACHINE`.  Additional control

"the term:`UBOOT_MACHINE` variable."

> +      variables can found at: :term:`UBOOT_CONFIG_BINARY`,

s/can found at:/are:/

> +      :term:`UBOOT_CONFIG_FRAGMENTS`, :term:`UBOOT_CONFIG_IMAGE_FSTYPES`, and
> +      :term:`UBOOT_CONFIG_MAKE_OPTS`. 
>  
> -      Here is an example from the ``meta-freescale`` layer. ::
> +      Here is an updated example from the ``meta-freescale`` layer. ::
>  
>           UBOOT_CONFIG ??= "sdcard-ifc-secure-boot sdcard-ifc sdcard-qspi lpuart qspi secure-boot nor"
> +
>           UBOOT_CONFIG[nor] = "ls1021atwr_nor_defconfig"
> -         UBOOT_CONFIG[sdcard-ifc] = "ls1021atwr_sdcard_ifc_defconfig,,u-boot-with-spl-pbl.bin"
> -         UBOOT_CONFIG[sdcard-qspi] = "ls1021atwr_sdcard_qspi_defconfig,,u-boot-with-spl-pbl.bin"
> +         UBOOT_CONFIG[sdcard-ifc] = "ls1021atwr_sdcard_ifc_defconfig"
> +         UBOOT_CONFIG[sdcard-qspi] = "ls1021atwr_sdcard_qspi_defconfig"
>           UBOOT_CONFIG[lpuart] = "ls1021atwr_nor_lpuart_defconfig"
>           UBOOT_CONFIG[qspi] = "ls1021atwr_qspi_defconfig"
>           UBOOT_CONFIG[secure-boot] = "ls1021atwr_nor_SECURE_BOOT_defconfig"
> -         UBOOT_CONFIG[sdcard-ifc-secure-boot] = "ls1021atwr_sdcard_ifc_SECURE_BOOT_defconfig,,u-boot-with-spl-pbl.bin"
> +         UBOOT_CONFIG[sdcard-ifc-secure-boot] = "ls1021atwr_sdcard_ifc_SECURE_BOOT_defconfig"
> +
> +         UBOOT_CONFIG_BINARY[sdcard-ifc] = "u-boot-with-spl-pbl.bin"
> +         UBOOT_CONFIG_BINARY[sdcard-qspi] = "u-boot-with-spl-pbl.bin"
> +         UBOOT_CONFIG_BINARY[sdcard-ifc-secure-boot] = "u-boot-with-spl-pbl.bin"
>  
>        In this example, all possible seven configurations are selected. Each
>        configuration specifies "..._defconfig" as :term:`UBOOT_MACHINE`, and
>        the "sd..." configurations define an individual name for
> -      :term:`UBOOT_BINARY`. No configuration defines a second parameter for
> -      :term:`IMAGE_FSTYPES` to use for the U-Boot image.
> +      :term:`UBOOT_CONFIG_BINARY`.
>  
>        For more information on how the :term:`UBOOT_CONFIG` is handled, see the
>        :ref:`ref-classes-uboot-config` class.
>  
> +   :term:`UBOOT_CONFIG_BINARY`
> +      This variable cannot be set to a value in a config, it is a placeholder
> +      for configuring the :term:`UBOOT_CONFIG` flow via flags::
> +
> +         UBOOT_CONFIG_BINARY[foo] = "binary1"
> +         UBOOT_CONFIG_BINARY[bar] = "binary2"
> +
> +      Specify the binary to select as the one to deploy in :term:`DEPLOY_DIR_IMAGE`.
s/Specify/It specifies/


> +      The output of a U-Boot build may be more than one binary, for example::
> +
> +         u-boot.bin
> +         u-boot-with-spl.bin
> +
> +      Setting the ``binary`` value to ``u-boot-with-spl.bin`` will make this
> +      binary the one deployed in :term:`DEPLOY_DIR_IMAGE`. It is renamed to
> +      include the build configuration name in the process (``foo`` or ``bar`` in
> +      the above example).
> +
> +      This option defaults to :term:`UBOOT_BINARY` if not specified.
> +
> +      For more information on how the :term:`UBOOT_CONFIG_BINARY` is handled, see the

"the :term:`UBOOT_CONFIG_BINARY` variable"

> +      :ref:`ref-classes-uboot-config` class.
> +
> +   :term:`UBOOT_CONFIG_FRAGMENTS`
> +      This variable cannot be set to a value in a config, it is a placeholder
> +      for configuring the :term:`UBOOT_CONFIG` flow via flags::
> +
> +         UBOOT_CONFIG_FRAGMENTS[foo] = "frag1 frag2"
> +         UBOOT_CONFIG_FRAGMENTS[bar] = "frag3"

> +
> +      Specify a list of fragments from the source tree that should be combined

s/Specify/It specifies/

> +      with the defconfig from :term:`UBOOT_CONFIG` that are used during ``do_configure()``
> +      to configure the build.

Can we specify from what these fragments paths are relative to? ${S}?

> +
> +      This option is not required and you only need to specify flag settings for

s/to specify flag settings/to specify it/ ?

> +      configs that need them.
> +
> +      For more information on how the :term:`UBOOT_CONFIG_FRAGMENTS` is handled, see the
> +      :ref:`ref-classes-uboot-config` class.
> +
> +   :term:`UBOOT_CONFIG_IMAGE_FSTYPES`
> +      This variable cannot be set to a value in a config, it is a placeholder
> +      for configuring the :term:`UBOOT_CONFIG` flow via flags::
> +
> +         UBOOT_CONFIG_IMAGE_FSTYPES[foo] = "fstype1"
> +         UBOOT_CONFIG_IMAGE_FSTYPES[bar] = "fstype2"
> +
> +      Append additional image types to the :term:`IMAGE_FSTYPES` variable for
> +      image generation for this build configuration.  This can allow building an
> +      extra image format that uses the binary generated by this build configuration.
> +
> +      This option is not required and you only need to specify flag settings for
> +      configs that need them.
> +
> +      For more information on how the :term:`UBOOT_CONFIG_IMAGE_FSTYPES` is handled, see the
> +      :ref:`ref-classes-uboot-config` class.
> +
> +   :term:`UBOOT_CONFIG_MAKE_OPTS`
> +      This variable cannot be set to a value in a config, it is a placeholder
> +      for configuring the :term:`UBOOT_CONFIG` flow via flags::
> +
> +         UBOOT_CONFIG_MAKE_OPTS[foo] = "OPT1=foo OPT2=2"
> +         UBOOT_CONFIG_MAKE_OPTS[bar] = "OPT1=bar"
> +
> +      Specify a list of make command line options that are passed to the ``make`` command

s/Specify/It specifies/

> +      during ``do_compile()``.
> +
> +      This option is not required and you only need to specify flag settings for
> +      configs that need them.
> +
> +      For more information on how the :term:`UBOOT_CONFIG_MAKE_OPTS` is handled, see the
> +      :ref:`ref-classes-uboot-config` class.
> +
>     :term:`UBOOT_DTB_LOADADDRESS`
>        Specifies the load address for the dtb image used by U-Boot. During FIT
>        image creation, the :term:`UBOOT_DTB_LOADADDRESS` variable is used in
> @@ -10980,6 +11059,12 @@ system and gives an overview of their function and contents.
>  
>        See the :ref:`ref-classes-uboot-sign` class for details.
>  
> +   :term:`UBOOT_FRAGMENTS`
> +      The :term:`UBOOT_FRAGMENTS` variable can be used to pass extra config
> +      fragments from the source tree to ``make`` when U-Boot is configured.

Once again we should specify from what the paths here are relative to, and maybe
provide an example. Maybe somewhat of a realistic example, maybe with a path
leading to some configuration name. Any existing fragment in mainline U-boot
maybe?

> +
> +      See the :ref:`ref-classes-uboot-config` class for more information.
> +
>     :term:`UBOOT_INITIAL_ENV_BINARY`
>        This variable enables the generation of the U-Boot initial environment in
>        binary format.

Thanks a lot for the patch!
Antonin