Astra Yocto Linux Developer Guide

Overview

This guide describes Synaptics specific configurations and procedures required to build and use Yocto images with the supported Synaptics SoC and development boards.

This guide assumes that the reader already has some familiarity with Yocto concepts. For introductory material about Yocto and general Yocto reference guides, please refer to the official Yocto Documentation.

This BSP works with the Yocto Kirkstone release and provides support for the following machines, distributions and images:

Supported machines, distributions and images
Machine	Distribution	Images
sl1620	poky	astra-media
sl1640	poky	astra-media
sl1680	poky	astra-media

Build host requirements

The recommended hardware is a x86_64 host with at least:

16 cores

32 GB of RAM

150 GB of disk

As an example, building from scratch the astra-media image for vs640 on a c5a.4xlarge AWS instance, which matches the requirements above, takes approximately 2 hours.

The Yocto build system can very efficiently exploit more cores if these are available.

Note

Building entirely from NFS mounted directories is not supported by the Yocto build system. Please refer to Yocto documentation on the TMPDIR variable for more details.

The recommended software configuration is the following:

Ubuntu 22.04 LTS

Docker 20.10 or later provided by the standard Ubuntu package docker.io

Other versions of Linux and Docker may also work but may need special configuration. You can find more information on how to install Docker in Ubuntu in Docker setup.

The Synaptics Astra SDK is known to work also on Ubuntu 22.04 installed inside Windows Subsystem For Linux (WSL) 2.0 on Windows 11. You can find more information on how to install WSL2 in WSL 2 Setup (required only when using Windows).

The build can also be executed directly on a Linux host provided that the Yocto build dependencies are installed. This configuration is not supported by Synaptics.

WSL 2 Setup (required only when using Windows)

Note

If you previously installed WSL1, installed another WSL2 distribution or disabled the hyper-v support on your machine you may need to perform some additional steps. See the Troubleshooting section for some suggested steps.

First install Windows Subsystem for Linux with the following command in PowerShell (as administrator):

PS C:\Users\username> wsl --install

This command will setup WSL and the default distribution which is Ubuntu 22.04 at the time of writing. You can find more details on installation procedure the WSL website.

By default WSL only uses up to 50% of the RAM of the host, this may not be enough to reach the memory required to build an image. If that’s the case you can in increase the memory adding the following to the file .wslconfig in your user directory (normally C:\Users\<Username):

[wsl2]
memory=24GB

Then to apply the changes in powershell run the command:

PS C:\Users\username> wsl.exe --shutdown

You can find more information about WSL configuration here.

Once you setup the WSL2 environment you can start a terminal from the start menu by selecting the Windows Terminal App and then select the Ubuntu-22.04 distribution.

Once you are in the terminal you can install Docker as described in Docker setup

Docker setup

To install docker use the following steps:

Install the docker package:
```
$ sudo apt install docker.io
```
Add the current user to the docker group so that it will be able to use docker:
```
$ sudo adduser ${USER} docker
```
The change of user will not be automatically applied until a reboot (in some situation a log-in may suffice). To apply the changes to the current shell you can also run the following command:
```
$ newgrp docker
$ newgrp ${USER}
```

How to build an image

Start the build environment

Note

The following steps require an hosts with docker correctly installed, you can find more information on how to setup docker in Build host requirements.

Warning

When using WSL2 build from /mnt/c and other host file system drives is not supported. Your build folder must reside on the native WSL2 file system (e.g. /home/${USER})

In order to ensure a correctly configured and clean environment, the build must be performed within a Docker container. To do so you need to start a new temporary container that will host the build. The container can be terminated when the build is finished and a new container can be started later to rebuild with the same command.

To start the container use the following command line:

$ docker run --rm -it -v $(pwd):$(pwd) ghcr.io/synaptics-astra/crops:0.9.0 --workdir=$(pwd)

This will spawn a shell inside the container. The current directory of the host is mounted inside the container so that the workspace is available within the container.

Note

On Ubuntu 20 and 18 LTS the seccomp protection feature of docker has to be disabled when creating the build container by adding the parameter --security-opt "seccomp=unconfined" after the --rm parameter in the command line above.

Note

Synaptics provides a pre-built container at ghcr.io/synaptics-astra/crops that is automatically downloaded when you run the command above but you can also compile from the sources available here.

Obtain the sources

The sources of the Synaptics Yocto release can be downloaded by cloning a top level git repo. The repository contains all the required layers as submodules.

To clone the repository within the build environment started with the instructions in Start the build environment use the following command:

pokyuser@xyz:/path/to/workspace $ git clone -b v0.9.0 --recurse-submodules \
                                            https://github.com/synaptics-astra/sdk

The recipes contained in the meta-synaptics layer point to the relevant git repository and will be downloaded using the standard bitbake fetching mechanism of Yocto.

Build an image

To build an image execute the following commands:

pokyuser@xyz:/path/to/workspace $ cd sdk

pokyuser@xyz:/path/to/workspace/sdk $ source meta-synaptics/setup/setup-environment

pokyuser@xyz:/path/to/workspace/sdk/build-XYZ $ bitbake astra-media

The resulting image can be found in build-${MACHINE}/tmp/deploy/images/${MACHINE}/SYNAIMG/.

The image can be flashed to an evaluation kit board as described in Updating the Firmware.

After flashing the board, to log in to the board please refer to Linux OS Login.

How to develop an application

One of the key features of the Yocto project is the ability to create a standalone SDK that includes everything you need to develop and test applications for a given target image.

The standalone toolchain is a precompiled set of tools, libraries, and headers that match the configuration of your Yocto Project build. It provides a consistent and controlled development environment that closely mirrors the target system. This ensures that the applications you develop will be compatible with the specific image that you’re deploying on your embedded devices.

Using the standalone toolchain, you can compile on your development machine before deploying them to the target device. This can greatly speed up the development process, as you don’t need to compile the entire image each time you want to test a change.

Pre-compiled toolchains for the default Astra Machina images are also available on GitHub.

Once you obtained the toolchain, you can install it on your development machine. The toolchain includes a script that sets up the environment variables needed to use the tools. The recommended and supported configuration of the development machine is the same as described in Build host requirements but the toolchain is compatible with a wide range of environments.

To setup the toolchain you first uncompress it as follows:

$ ./poky-glibc-x86_64-astra-media-${CPUTYPE}-${MACHINE}-toolchain-4.0.9.sh
Poky (Yocto Project Reference Distro) SDK installer version 4.0.9
=================================================================
Enter target directory for SDK (default: /opt/poky/4.0.9): toolchain
You are about to install the SDK to "/home/user/toolchain". Proceed [Y/n]?
Extracting SDK.................................................................................................................................................................................................................................................................................................................................done
Setting it up...done
SDK has been successfully set up and is ready to be used.
Each time you wish to use the SDK in a new shell session, you need to source the environment setup script e.g.
  $ . /home/user/toolchain/environment-setup-armv7at2hf-neon-vfpv4-pokymllib32-linux-gnueabi
  $ . /home/user/toolchain/environment-setup-cortexa73-poky-linux

The exact names of the toolchain environment files depend on the target board: CPUTYPE for sl1680 is cortexa73, for sl1620 and sl1640 is cortexa55

Then to configure the build environment you need to source a configuration script as follows:

$ . toolchain/environment-setup-${CPUTYPE}-poky-linux

With the environment setup, you can use the provided cross-compiler to compile your applications. The toolchain also includes libraries and headers for the various components included in the image, so you can develop applications that take full advantage of these components. You can use the environment variables set by the script such as CC to invoke the cross-compiler and build your application with it.

More information about the standalone toolchain are available in the Yocto documentation.

How to re-build a standalone toolchain

You can re-generate a toolchain in your Yocto build environment configured as described in How to build an image by running the following command:

pokyuser@xyz:/path/to/workspace $ cd sdk

pokyuser@xyz:/path/to/workspace/sdk $ source meta-synaptics/setup/setup-environment

pokyuser@xyz:/path/to/workspace/sdk/build-XYZ $ bitbake astra-media -c do_populate_sdk

The build proces will generate the toolchain in the directory build-${MACHINE}/tmp/deploy/sdk.

Compatible Layers

This BSP is compatible with these layers:

poky [branch: kirkstone]

meta-openembedded [branch: kirkstone]

meta-oe (required by meta-python below)

meta-python (required by meta-multimedia below)

meta-multimedia (optional - for gstreamer support)

meta-qt [branch qt/upstream/kirkstone ] (optional)

Images

`astra-media`

The astra-media image, based on the poky distribution, provides a basic graphical system with weston and it is suitable to test sl1640 and sl1680 features.

The image requires some specific configurations in conf/local.conf to work correctly. The meta-synaptics/setup/setup-environment script can be used to correctly setup a astra-media build automatically.

For more details about these configurations please refer to the comments in the sample local.conf found in meta-synaptics/setup/conf/local.conf.sample.

In order to be able to run qt application on wayland the following package must also be added. This must be enable manually even when using setup/setup-environment:

DISTRO_EXTRA_RDEPENDS:append = " qtwayland"

Configuration

Kernel command line

The kernel command line is defined by the variable CMDLINE of the linux-syna recipe.

System Memory configuration

System memory configuration is performed by changing the variables CONFIG_PREBOOT_ in the configuration file pointed by SYNA_SDK_CONFIG_FILE variable. The available configurations can be found by inspecting https://github.com/synaptics-astra/boot-preboot-prebuilts .

Partition tables

Partition tables are configured in the file emmc.pt found in the directory product/${SYNA_SDK_CONFIG_NAME}/emmc.pt found at http://github.com/synaptics-astra/configs . The SYNA_SDK_CONFIG_NAME depends on the MACHINE and DISTRO_CONFIG variables.

To customize this file you can override the recipe syna-config-native.

Some partitions are used by the early boot components stored in eMMC boot partition. These partitions cannot be removed but can be moved. The early boot components locate these partitions using the GPT found in the UDA. Loading from other hardware partitions is not supported.

Frequently Asked Questions

How do I override the value of to a recipe variable in local.conf?

To append the text some text to the variable FOO of recipe bar add the following line to local.conf:
FOO:append:pn-bar = " some text"
Other changes to the variable can be performed with the standard operators described in the Bitbake Guide.

Troubleshooting

The build fails at the package gdk-pixbuf-native with error Failed to close file descriptor for child process on Ubuntu 20 or 18.

This problem is caused by an incompatibility of the package build system with the libseccomp library on the host that is running docker. To solve this issue update the libseccomp2 library on the host that runs docker or add the parameter --security-opt "seccomp=unconfined to the docker command line when creating the docker build environment.

Build of packages with out-of-trees modules (such as synasdk-synap-module) fail with error Kernel configuration is invalid..

Under some circumstances the state of the recipe make-mod-scripts may become corrupted. To fix the issue clean the recipe with the command:
bitbake -c cleansstate make-mod-scripts

Docker commands fail with the error permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get "http://%2Fvar%2Frun%2Fdocker.sock/v1.24/version": dial unix /var/run/docker.sock: connect: permission denied

Make sure your user is in the docker group:
$ getent group docker
docker:x:133:yourusername
and that your current session is logged in to the docker group:
$ id
uid=1000(yourusername) gid=1000(yourusername) groups=1000(yourusername),133(docker)
To add your user to the docker group user the following command:
$ sudo adduser yourusername docker
To ensure your session logged in to the docker group use the following command:
$ newgrp docker

The build fails on WSL2 when building from /mnt/c

The Yocto build requires a case-sensitive file system. By default WSL2 mounts of the C: drive found in /mnt/c is not. This leads to the following error:
pokyuser@868531cb885f:/mnt/c/work/astra/sdk/build-sl1680$ bitbake astra-media
WARNING: You are running bitbake under WSLv2, this works properly but you should optimize your VHDX file eventually to avoid running out of storage space
ERROR:  OE-core's config sanity checker detected a potential misconfiguration.
    Either fix the cause of this error or at your own risk disable the checker (see sanity.conf).
    Following is the list of potential problems / advisories:
The TMPDIR (/mnt/c/work/astra/sdk/build-sl1680/tmp) can't be on a case-insensitive file system.
To solve this problem, either setup the build in the WSL2 home directory (i.e. cd ~) or enable case-sensitive on the main Windows file system with the following command in an admin PowerShell:
PS C:> fsutil.exe file SetCaseSensitiveInfo C:\work\astra\sdk
Where C:\work\astra\sdk\ is the directory containing the sdk repository clone.

WSL2 is not working correctly on my Windows machine

You may try the following things to reset the state on your machine:
Enable the Windows Subsystem for Linux:
PS C:\Users\username> dism.exe /online /enable-feature /featurename:Microsoft-Windows-Subsystem-Linux /all /norestart
Enable Virtual Machine feature:
PS C:\Users\username> dism.exe /online /enable-feature /featurename:VirtualMachinePlatform /all /norestart
Restart your PC

Download the Linux kernel update package and install it
Set WSL 2 as default version:
PS C:\Users\username> wsl --set-default-version 2
Install Ubuntu 22.04 LTS from Microsoft Store
Set default distro to Ubuntu-22.04:
PS C:\Users\username> wsl --set-default Ubuntu-22.04

Astra Yocto Linux Developer Guide

Overview

Build host requirements

WSL 2 Setup (required only when using Windows)

Docker setup

How to build an image

Start the build environment

Obtain the sources

Build an image

How to develop an application

How to re-build a standalone toolchain

Compatible Layers

Images

astra-media

Configuration

Kernel command line

System Memory configuration

Partition tables

Frequently Asked Questions

Troubleshooting

`astra-media`