Re: [PATCH v2] kernel-dev: document KCONFIG_MODE

["Quentin Schulz" <quentin.schulz@streamunlimited.com>]

Hi Daniel,

Many thanks for the v2!

On Wed, May 05, 2021 at 10:57:50AM +0200, Daniel Wagenknecht wrote:
> Signed-off-by: Daniel Wagenknecht <dwagenknecht@emlix.com>
> ---
>  documentation/kernel-dev/common.rst    |  9 ++++++
>  documentation/ref-manual/variables.rst | 38 ++++++++++++++++++++++++++
>  2 files changed, 47 insertions(+)
> 
> diff --git a/documentation/kernel-dev/common.rst b/documentation/kernel-dev/common.rst
> index 3f35d8412..5935d6f56 100644
> --- a/documentation/kernel-dev/common.rst
> +++ b/documentation/kernel-dev/common.rst
> @@ -650,6 +650,15 @@ extends the :term:`FILESPATH`
>  variable (search directories) to include the ``${PN}`` directory you
>  created to hold the configuration changes.
>  
> +You can also use a regular ``defconfig`` file, as generated by the
> +:ref:`ref-tasks-savedefconfig`
> +task instead of a complete ``.config`` file. This only specifies the
> +non-default configuration values.  You need to additionally set
> +:term:`KCONFIG_MODE`
> +in the linux-yocto ``.bbappend`` file in your layer::
> +
> +   KCONFIG_MODE = "alldefconfig"
> +
>  .. note::
>  
>     The build system applies the configurations from the ``defconfig``
> diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst
> index c339d45e1..a2db34520 100644
> --- a/documentation/ref-manual/variables.rst
> +++ b/documentation/ref-manual/variables.rst
> @@ -3745,6 +3745,44 @@ system and gives an overview of their function and contents.
>        ":ref:`kernel-dev/common:using an "in-tree" \`\`defconfig\`\` file`"
>        section in the Yocto Project Linux Kernel Development Manual.
>  
> +   :term:`KCONFIG_MODE`
> +      When used with the :ref:`kernel-yocto <ref-classes-kernel-yocto>`
> +      class, specifies the kernel configuration values to use for options
> +      not specified in the provided ``defconfig`` file. Valid options are::
> +
> +         KCONFIG_MODE = "alldefconfig"
> +         KCONFIG_MODE = "allnoconfig"
> +
> +      In ``alldefconfig`` mode the options not explicitely specified will be
> +      assigned their Kconfig default value. In ``allnoconfig`` mode the
> +      options not explicitely specified will be disabled in the kernel
> +      config.
> +
> +      In case ``KCONFIG_MODE`` is unset the behaviour will depend on where
> +      the ``defconfig`` file is coming from. An "in-tree" ``defconfig`` file
> +      will be handled in ``alldefconfig`` mode, a ``defconfig`` file placed
> +      in ``${WORKDIR}`` through a meta-layer will be handled in
> +      ``allnoconfig`` mode.
> +
> +      An "in-tree" ``defconfig`` file can be selected via the
> +      :term:`KBUILD_DEFCONFIG` variable. ``KCONFIG_MODE`` does not need to
> +      be explicitely set.
> +
> +      A ``defconfig`` file compatible with ``allnoconfig`` mode can be
> +      generated by copying the ``.config`` file from a working Linux kernel
> +      build, renaming it to ``defconfig`` and placing it into the Linux
> +      kernel ``${WORKDIR}`` through your meta-layer. ``KCONFIG_MODE`` does
> +      not need to be explicitely set.

s/explicitely/explicitly/

> +
> +      A ``defconfig`` file compatible with ``alldefconfig`` mode can be
> +      generated using the
> +      :ref:`ref-tasks-savedefconfig`
> +      task and placed into the Linux kernel ``${WORKDIR}`` through your
> +      meta-layer. Explicitely set ``KCONFIG_MODE``::
> +

s/Explicitely/Explicitly/

Otherwise:
Reviewed-by: Quentin Schulz <foss@0leil.net>

Thanks!
Quentin