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ref-manual: classes.rst: document devicetree.bbclass

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This addresses [YOCTO #15092]

(From yocto-docs rev: f65816f5ea62e6c4301c0bd0c6aad91110963f9e)

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Michael Opdenacker
2023-04-04 19:35:43 +02:00
committed by Richard Purdie
parent 878271e1a1
commit edb884a7ed
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@@ -580,6 +580,49 @@ add the task at the appropriate place, which is usually after
:ref:`ref-tasks-install`. The class then takes care of
staging the files from :term:`DEPLOYDIR` to :term:`DEPLOY_DIR_IMAGE`.
.. _ref-classes-devicetree:
``devicetree``
==============
The :ref:`ref-classes-devicetree` class allows to build a recipe that compiles
device tree source files that are not in the kernel tree.
The compilation of out-of-tree device tree sources is the same as the kernel
in-tree device tree compilation process. This includes the ability to include
sources from the kernel such as SoC ``dtsi`` files as well as C header files,
such as ``gpio.h``.
The :ref:`ref-tasks-compile` task will compile two kinds of files:
- Regular device tree sources with a ``.dts`` extension.
- Device tree overlays, detected from the presence of the ``/plugin/;``
string in the file contents.
This class behaves in a similar way as the :ref:`ref-classes-kernel-devicetree`
class, also deploying output files into ``/boot/devicetree``. However, this
class stores the deployed device tree binaries into the ``devicetree``
subdirectory. This avoids clashes with the :ref:`ref-classes-kernel-devicetree`
output. Additionally, the device trees are populated into the sysroot for
access via the sysroot from within other recipes.
An extra padding is appended to non-overlay device trees binaries. This
can typically be used as extra space for adding extra properties at boot time.
The padding size can be modified by setting ``DT_PADDING_SIZE`` to the desired
size, in bytes.
See :oe_git:`devicetree.bbclass sources
</openembedded-core/tree/meta/classes-recipe/devicetree.bbclass>`
for further variables controlling this class.
Here is an excerpt of an example ``recipes-kernel/linux/devicetree-acme.bb``
recipe inheriting this class::
inherit devicetree
COMPATIBLE_MACHINE = "^mymachine$"
SRC_URI:mymachine = "file://mymachine.dts"
.. _ref-classes-devshell:
``devshell``