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diff --git a/documentation/overview-manual/overview-manual-concepts.xml b/documentation/overview-manual/overview-manual-concepts.xml
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--- a/documentation/overview-manual/overview-manual-concepts.xml
+++ b/documentation/overview-manual/overview-manual-concepts.xml
@@ -580,64 +580,92 @@
This section takes a closer look at the layers the build system
uses to further control the build.
These layers provide Metadata for the software, machine, and
- policy.
+ policies.
- In general, three types of layer input exist:
+ In general, three types of layer input exists.
+ You can see them below the "User Configuration" box in the
+ general workflow figure:
- Policy Configuration:
- Distribution Layers provide top-level or general
- policies for the image or SDK being built.
- For example, this layer would dictate whether BitBake
- produces RPM or IPK packages.
+ Metadata (.bb + Patches):
+ Software layers containing user-supplied recipe files,
+ patches, and append files.
+ A good example of a software layer might be the
+ meta-qt5
+ layer from the
+ OpenEmbedded Layer Index.
+ This layer is for version 5.0 of the popular
+ Qt
+ cross-platform application development framework for
+ desktop, embedded and mobile.
- Machine Configuration:
- Board Support Package (BSP) layers provide machine
+ Machine BSP Configuration:
+ Board Support Package (BSP) layers (i.e. "BSP Layer"
+ in the following figure) providing machine-specific
configurations.
This type of information is specific to a particular
target architecture.
+ A good example of a BSP layer from the
+ Poky Reference Distribution
+ is the
+ meta-yocto-bsp
+ layer.
- Metadata:
- Software layers contain user-supplied recipe files,
- patches, and append files.
+ Policy Configuration:
+ Distribution Layers (i.e. "Distro Layer" in the
+ following figure) providing top-level or general
+ policies for the images or SDKs being built for a
+ particular distribution.
+ For example, in the Poky Reference Distribution the
+ distro layer is the
+ meta-poky
+ layer.
+ Within the distro layer is a
+ conf/distro directory that
+ contains distro configuration files (e.g.
+ poky.conf
+ that contain many policy configurations for the
+ Poky distribution.
- The following figure shows an expanded representation of the
- Metadata, Machine Configuration, and Policy Configuration input
- (layers) boxes of the
+ The following figure shows an expanded representation of
+ these three layers from the
general workflow figure:
-
-
-
-
+
In general, all layers have a similar structure.
They all contain a licensing file
- (e.g. COPYING) if the layer is to be
+ (e.g. COPYING.MIT) if the layer is to be
distributed, a README file as good
practice and especially if the layer is to be distributed, a
configuration directory, and recipe directories.
+ You can learn about the general structure for layers used with
+ the Yocto Project in the
+ "Creating Your Own Layer"
+ section in the Yocto Project Development Tasks Manual.
+ For a general discussion on layers and the many layers from
+ which you can draw, see the
+ "Layers" and
+ "The Yocto Project Layer Model"
+ sections both earlier in this manual.
- The Yocto Project has many layers that can be used.
- You can see a web-interface listing of them on the
+ If you explored the previous links, you discovered some
+ areas where many layers that work with the Yocto Project
+ exist.
+ The
Source Repositories
- page.
- The layers appear at the bottom categorized under
- "Yocto Metadata Layers."
- These layers are fundamentally a subset of the
- OpenEmbedded Layer Index,
- which lists all layers provided by the OpenEmbedded community.
+ also shows layers categorized under "Yocto Metadata Layers."
Layers exist in the Yocto Project Source Repositories that
cannot be found in the OpenEmbedded Layer Index.
@@ -652,12 +680,6 @@
should be using as part of the build.
-
- For more information on layers, see the
- "Understanding and Creating Layers"
- section in the Yocto Project Development Tasks Manual.
-
-
Distro Layer
@@ -704,6 +726,16 @@
to add distribution-specific configuration,
initialization scripts, custom image recipes,
and so forth.
+ Examples of recipes-*
+ directories are recipes-core
+ and recipes-extra.
+ Hierarchy and contents within a
+ recipes-* directory can vary.
+ Generally, these directories contain recipe files
+ (*.bb), recipe append files
+ (*.bbappend), directories
+ that are distro-specific for configuration files,
+ and so forth.
@@ -713,7 +745,8 @@
BSP Layer
- The BSP Layer provides machine configurations.
+ The BSP Layer provides machine configurations that
+ target specific hardware.
Everything in this layer is specific to the machine for
which you are building the image or the SDK.
A common structure or form is defined for BSP layers.
@@ -738,8 +771,8 @@
The remainder of the layer is dedicated to specific recipes
by function: recipes-bsp,
recipes-core,
- recipes-graphics, and
- recipes-kernel.
+ recipes-graphics,
+ recipes-kernel, and so forth.
Metadata can exist for multiple formfactors, graphics
support systems, and so forth.
@@ -762,8 +795,8 @@
- This layer contains any new recipes that your project
- needs in the form of recipe files.
+ This layer contains any recipes, append files, and
+ patches, that your project needs.