View source for How to compile the device tree with the Distribution Package

{{InternalInfo|This article can be reviewed but not moved to APPROVED state
What is described below will be delivered after MMDV, planned with maintenance version V1.1.0}}
==Introduction==
This article is intended for Yocto experts, or people who have some practical experience of the Yocto environmment.<br><br>
This section describes the steps needed to create and configure a demo layer using DeviceTree files from the STM32CubeMX tool, and to add and configure a machine similar to those already supported by the OpenSTLinux Distribution Package (in particular the machine delivered inside the existing STM32MP BSP layer 'addons').<br>

Reminder: this addon-layer is deployed under the following path in the delivery : '''<path of OpenSTLinux distribution delivery>/layers/meta-st/meta-st-stm32mp-addons/'''

==Creating a new open embedded layer for your demo==
You first need to create a new layer. See the latest  [[How to create a new open embedded layer]]<br><br>
After creation, you have under '''<path of OpenSTLinux distribution delivery>/layers/meta-st/''':

<pre>
$ tree meta-my-demo-layer
meta-my-demo-layer
├── conf
│   └── layer.conf
├── COPYING.MIT
├── README
└── recipes-example
    └── example
        └── example.bb

3 directories, 4 files
</pre>

===Update layer.conf file===
Open the layer.conf file and add the lines below for the licenses,  demo layer path, and dependency with the STM32MP BSP layer 'addons' :

 EULA_FILE_ST_{{Highlight|stm32mpmydemo}} = "${LAYERDIR}/conf/eula/${MACHINE}"
 EULA_FILE_ST_MD5SUM_{{Highlight|stm32mpmydemo}} = "8b505090fb679839cefbcc784afe8ce9"
 
 #Inform bitbake for adding another location to search for licenses
 LICENSE_PATH += "${LAYERDIR}/files/licenses"
 
 # Set a variable to get the STM32MP MX BSP location
 {{Highlight|STM32MP_MY_DEMO_BASE}} = "${LAYERDIR}"
 
 # This should only be incremented on significant changes that may
 # cause compatibility issues with other layers
 LAYERVERSION_meta-my-demo-layer = "1"
 
 LAYERDEPENDS_meta-my-demo-layer = "{{Highlight|stm-st-stm32mp-mx}}"
 
 # OpenEmbedded compatibility information
 # This should only be incremented on significant changes that will
 # cause compatibility issues with other layers
 LAYERVERSION_meta-my-demo-layer = "1"
 LAYERSERIES_COMPAT_meta-my-demo-layer = "thud"

{{Info| LAYERSERIES_COMPAT must be aligned with the version of OpenEmbedded used.<br>Please refer to https://wiki.yoctoproject.org/wiki/Releases}}

===Create the machine for your demo===
* Copy the machine delivered inside the existing STM32MP BSP layer 'addons' into your demo layer

 $ cp <path of OpenSTLinux distribution delivery>/layers/meta-st/meta-st-stm32mp-addons/conf/machine/'''stm32mp1-mx.conf''' <path of OpenSTLinux distribution delivery>/layers/meta-st/meta-my-demo-layer/conf/machine/'''stm32mp1-demo.conf'''

* Open stm32mp1-demo.conf and update the line below
 #@NEEDED_BSPLAYERS: layers/meta-openembedded/meta-oe layers/meta-openembedded/meta-python {{Highlight|layers/meta-st/meta-st-stm32mp-addons}}

* Replace STM32MP_MX_BASE by {{Highlight|STM32MP_MY_DEMO_BASE}}

* Add these lines after the series of includes: 

 # Define specific common machine name
 MACHINEOVERRIDES .= ":{{Highlight|stm32mpmydemo}}"

* Uncomment variables to configure your own {{Highlight|Boot Mode Choice}}, {{Highlight|Boot Device Choice}},  {{Highlight|Board Type Choice, DeviceTree files and path}}

===Associate EULA with the new demo machine===
Copy the eula folder delivered inside the existing STM32MP BSP layer 'addons' into your demo layer 

 $ cp -rf <path of OpenSTLinux distribution delivery>/layers/meta-st/meta-st-stm32mp-addons/conf/'''eula'''/ <path of OpenSTLinux distribution delivery>/layers/meta-st/meta-my-demo-layer/conf/.

Then replace the existing symbolic link with the machine used for your demo:

 $ rm stm32mp1-mx
 $ ln -s ST_EULA_SLA stm32mp1-demo

===Move DeviceTree files and project coming from STM32CubeMX tool===
The principle is that the user generates devicetree files for the targeted demo from the STM32CubeMX tool.
{{Warning|'''Most of the time, generated devicetree files - mainly user sections - must be reworked by the end user for compilation and functional purposes. Each demo is delivered with an application note that describe changes applied on STM32CubeMX devicetree files'''}}.
{{InternalInfo|For a motor control demo the application note is located [https://epm-st.st.com/ProjectServerST/Wildcat%20APPLI%20Introduction%20Package/Working%20Documents/Support%20and%20Application/Demonstrations/MotorControlAN_v1.01.docx here]}}
These files are then moved into the “mx” folder created into your demo layer  : '''<path of OpenSTLinux distribution delivery>/layers/meta-st/meta-my-demo-layer/mx/'''

Sub-folders are created and populated with the generated devicetree files:
 mx/${CUBEMX_PROJECT}/kernel
 mx/${CUBEMX_PROJECT}/u-boot
 mx/${CUBEMX_PROJECT}/tf-a
 mx/${CUBEMX_PROJECT}/optee-os

With {{Highlight|CUBEMX_PROJECT}} that is equal to the value defined inside the machine used for the demo.

===Update the README file===
Please update the README file with the information needed for building and executing the demo.

===Clean up useless content===
You can delete the content of the recipes-example folder created by the create-layer command.

After making all of the updates, your demo layer should be similar to:

<pre>
$ tree meta-my-demo-layer
meta-my-demo-layer
├── conf
│   └── eula
│       └── ST_EULA_SLA
│       └── stm32mp1-demo -> ST_EULA_SLA
│       └──  ...
│   └── layer.conf
│   └── machine
│       └── stm32mp1-demo.conf
├── COPYING.MIT
├── mx
│   └── STM32MP157C-EV1
│        └── my-demo
│            └── DeviceTree
│                └── my-demo
│                    └── kernel
│                        └── stm32mp157c-my-demo.dts
│                    └── tf-a
│                        └── stm32mp157c-my-demo.dts
│                        └── stm32mp15-mx.h
│                    └── u-boot
│                        └── stm32mp157c-my-demo.dts
│                        └── stm32mp157c-my-demo-u-boot.dtsi
│                        └── stm32mp15-mx.h
│                    └── optee-os
│                        └── stm32mp157c-my-demo.dts
└── README
</pre>

==Adding specific recipes and content necessary for your demo==

Examples of further add-on components: 
* Recipes for installing distro-specific configuration files
* Any image recipes specific to user distribution
* A ''psplash append file'' for a branded splash screen
* Any other append files to make custom changes

Some other added components (*bb) are more specific: images, system services, and so on (a non-exhaustive list is shown below):
* Recipes-core for ''psplash screen'', ''systemd services''
* Recipes-samples for example images
...<br>

<noinclude>
[[Category:How to customize software]]
{{PublicationRequestId | 12272| 2019-06-07}}
</noinclude>