ROS support in yocto standard SDK

[jiaxshi]

Backgroud:

Build ROS package from scratch in yocto takes much time. You can use an SDK to independently develop and test code that is destined to run on some target machine.

There are several github issues related to SDK support. And there's some work done by community members.
#1203
#988

I also did some work on kirkstone/humble, here are some issues/topics to be discussed.
#1215

Topics/issues

How to add SDK support: packagegroup or inc file

• Packagegroup
  Refer to Enable SDK for ROS2 Rolling #1203. A new image recipe and packagegroup is added for SDK.

• inc file
  I think SDK should be supported by default. Using a inc file and added in ros2.conf

diff --git a/meta-ros2/conf/distro/ros2.conf b/meta-ros2/conf/distro/ros2.conf
index 4fb656587..4178211a6 100644
--- a/meta-ros2/conf/distro/ros2.conf
+++ b/meta-ros2/conf/distro/ros2.conf
@@ -3,3 +3,4 @@
 DISTRO_NAME = "Robot Operating System 2 (ROS 2)"

 require conf/distro/include/ros-common.inc
+require conf/distro/include/ros2-sdk.inc

"nativesdk" in bbappends

Refer to 6670f76, we need some bbappends for adding "nativesdk".

Idea: a mechanism to add "nativesdk" in generated recipes.

Build issues in SDK

HOST path

• HOST path is included in cross compile
  Similar to {humble}: fix host path is included in cmake files. #1192, if host path is included in xxx-export.cmake makes build failured.

• Setup script
  No cross copile concept in python/colcon. So HOST path is using in artifacts of SDK output file

_colcon_prefix_chain_sh_COLCON_CURRENT_PREFIX=/local/mnt3/workspace/jiaxshi/projects/sdk/ws4/examples/install

Python C library naming

For example:

install/pendulum_msgs/lib/python3.10/site-packages/pendulum_msgs/pendulum_msgs_s__rosidl_typesupport_fastrtps_c.cpython-310-x86_64-linux-gnu.so

expected naming:

install/pendulum_msgs/lib/python3.10/site-packages/pendulum_msgs/pendulum_msgs_s__rosidl_typesupport_fastrtps_c.cpython-310-aarch64-linux-gnu.so

• Temp solution
  We can use cmake args to fix this issue.

-DPYTHON_SOABI=cpython-310-aarch64-linux-gnu

How to install packages generated by SDK?

ipk/deb packages are not generated by SDK.

How to run packages build by SDK? Similar on Ubuntu platform？

[sgstreet]

Using the SDK to build ROS2 packages

The ROS2 developers are used to sourcing the ROS2 setup.bash script and running colcon, something like this:

$ source /opt/ros/rolling/setup.bash
$ colcon build

To use the Yocto SDK you must source environment-setup-cortexa76-oe-linux script first, but the target sysroot setup.bash can not be used because it is not aware of the Yocto SDK structure. Following enivronment is need to use the SDK:

export ROS_VERSION=2
export ROS_PYTHON_VERSION=3
export ROS_AUTOMATIC_DISCOVERY_RANGE=SUBNET
export ROS_DISTRO=rolling
export PYTHONPATH=$OECORE_NATIVE_SYSROOT/usr/lib/python3.12/site-packages:$OECORE_TARGET_SYSROOT/opt/ros/rolling/lib/python3.12/site-packages
export AMENT_PREFIX_PATH=$OECORE_TARGET_SYSROOT/opt/ros/rolling
usr/share:$OECORE_TARGET_SYSROOT/opt/ros/rolling/share:$OECORE_TARGET_SYSROOT/opt/ros/rolling/lib/cmake"

Should these exports somehow be added to the SDK environment-setup-cortexa76-oe-linux script or should a meta-ros SDK setup.bash be generated?

To get colcon to use the SDK the following incantation is required:

$ colcon build \
--merge-install \
--install-base $PWD/install/arm64 \
--cmake-args \
" -DCMAKE_TOOLCHAIN_FILE=$CMAKE_TOOLCHAIN_FILE" \
" -DCMAKE_STAGING_PREFIX=$PWD/install/arm64" \
" -DBUILD_TESTING=OFF"

Should we meta-ros patch colcon to include the required cmake-args by default?