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[4/4] ref-manual: classes: kernel: document automatic defconfig usage

Message ID 20230509124038.2265185-4-michael.opdenacker@bootlin.com
State New
Headers show
Series [1/4,mickledore] migration-guides: release-notes-4.2: add doc improvement highlights | expand

Commit Message

Michael Opdenacker May 9, 2023, 12:40 p.m. UTC 
From: Michael Opdenacker <michael.opdenacker@bootlin.com>

From: Luca Ceresoli <luca.ceresoli@bootlin.com>

Since a very long time the kernel bbclass uses a defconfig file from
SRC_URI automatically. Document this feature.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
---
 documentation/ref-manual/classes.rst | 7 +++++++
 1 file changed, 7 insertions(+)
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Patch

diff --git a/documentation/ref-manual/classes.rst b/documentation/ref-manual/classes.rst
index de2d97de30..8f7cbf2b45 100644
--- a/documentation/ref-manual/classes.rst
+++ b/documentation/ref-manual/classes.rst
@@ -1532,6 +1532,13 @@  code to build all kernel trees. All needed headers are staged into the
 :term:`STAGING_KERNEL_DIR` directory to allow out-of-tree module builds
 using the :ref:`ref-classes-module` class.
 
+If a file named ``defconfig`` is listed in :term:`SRC_URI`, then by default
+:ref:`ref-tasks-configure` copies it as ``.config`` in the build directory,
+so it is automatically used as the kernel configuration for the build. This
+copy is not performed in case ``.config`` already exists there: this allows
+recipes to produce a configuration by other means in
+``do_configure:prepend``.
+
 Each built kernel module is packaged separately and inter-module
 dependencies are created by parsing the ``modinfo`` output.  If all modules
 are required, then installing the ``kernel-modules`` package installs all