How-to: Add meta layers to your BSP

This is a really handy link that is in the Quickstarts:

Summary

i.MX6 PD16.1.0

Yocto 2.1.2. (Krogoth)

Customizing Linux to fit a specific application is

The $YOCTO_DIR/sources directory contains the meta layers
Check OpenEmbedded for pre made layers

Create your layer

Download the standard BSP according to the Quickstart Guide for the product you are developing with
Source the build environment as stated in the Quickstart manual
Create a development directory at the root of your Yocto directory
- mkdir $YOCTO_DIR/development
  - <TODO>: need to set permissions
Create your meta layer and move it to the development directory with the following commands:
```
cd $YOCTO_DIR/build
yocto-layer create custom
mv meta-custom/ ../development/
```

Create a git repo and add your layer

cd $YOCTO_DIR/development/meta-custom/
git init && git add . && git commit -s

Configuring your layer

Set the layer priority to override the meta-phytec recipes and configuration

- Change priority to +1 of the meta-phytec layer priority
- You'll need to know the priority of the meta-phytec layer first. Use the command below to obtain the meta-phytec layer priority:

cat $YOCTO_DIR/sources/meta-phytec/conf/layer.conf | grep PRIORITY

- Use your favorite text editor to set your layer's priority to something greater than the priority of the meta-phytec layer

Create a machine configuration to describe your custom hardware

- create the machine directory
  - mkdir $YOCTO_DIR/development/meta-custom/conf/machine
- copy the machine configuration that closest describes your hardware

Note here about how to find your machine configuration

cp $YOCTO_DIR/sources/meta-phytec/conf/machine/<standard machine config name> $YOCTO_DIR/sources/meta-custom/conf/machine/<your custom machine config name>

Append the standard kernel and bootloader recipes to add support for your custom machine

- Make a .bbappend file for your kernel recipe
  - Create a recipes-kernel directory in the root of meta-custom
  - see .....sources/meta-phytec/recipes-kernel/linux/linux_mainline_x.x.x-phyx.bb
    - need to create a similar file in .....sources/meta-mycustomlayer/recipes-kernel/linux/ with a .bbappend filetype
    - add machine name as a COMPATIBLE_MACHINE

<TODO: add a picure of the *.bbappend recipe with just the COMPATIBLE_MACHINE assigned to the new machine config>

- Make a .bbappend file for your bootloader recipe
  - see ....sources/meta-phytec/recipes-bsp/<bootloader>/something.bb
    - need to create a similar file in .....sources/meta-mycustomlayer/recipes-bsp/<bootloader>/ with a .bbappend filetype
    - add machine name as a COMPATIBLE_MACHINE

<TODO: add a picure of the *.bbappend recipe with just the COMPATIBLE_MACHINE assigned to the new machine config>

Customize your layer

- For developing a custom device tree, clone the linux source, make changes, commit, create a patch, and add the patch to your meta layer kernel recipe.
- Specify your custom device tree
  - - This is done throught the KERNEL_DEVICETREE variable in the machine configuration file
    - Don't forget to add your custom device tree file to the Makefile in the device tree directory
- Specify your custom machine configuration
  - This is done through the MACHINE variable in the local.conf file in the build directory (DO NOT append .conf!!!)
- Add new files and commit modifications to your git repo
  - cd $YOCTO_DIR/sources/meta-custom
  - git add . && git commit -s
- Push your git repo to your remote repo
  - git push ....

Integrate your custom layer

- Using your favorite text editor, add your new layer to the bblayers.conf file (..../build/conf/bblayers.conf)

<TODO: add a picture of the bblayers.conf file, with custom layer appended>

Automating your build

Copy your current manifest
- ls -l $YOCTO_DIR/.repo/manifest.xml
- Copy the *.xml file linked to manifest.xml and give it a unique name
- Add your layer information to the new manifest
  - <remote fetch="<git repo URL that contains your layer source>" name="customlayer">
  - <prjoect name="<your layer name here, ex. meta-custom>" path="sources/<your layer name here, ex. meta-custom>" remote="customlayer" revision="<tag name, commit ID, etc...>">

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