I understand. Thanks for bringing this up. If you wish, you can share the compilation error with us and we can assist you in building the BSP 2.8 Image.
As the BSP 2.8 is the LTS and the latest commit mentions the Kernel version 4.4.291 and no other changes have been made to update it once more you may use this version without problems. It’s always recommended to use the most updated tools.
I’d recommend you to check the gitlog for Colibri VF linux-toradex.git - Linux kernel for Apalis, Colibri and Verdin modules. You can see there that the last commit was made in November 2021 and any update to this will be added on that same page. As this release is the LTS, Updates are not so frequent anymore. From the Support Strategy Page you can see the following LTS definition:
Maintenance Releases for Long Term Embedded Linux Release (LTS)
Toradex continuously maintains LTS releases by providing bug fixes and security patches:
In case there are any hardware changes required e.g because of a component going end-of-life, Toradex fully supports and validates the new hardware version and does any necessary software backports to support them.
Those updates are provided to customers as maintenance releases in the form of source code and binary images.
Toradex provides updates for the software components. They consist of fixed versions of the U-Boot boot loader, Linux kernel and OpenEmbedded/Yocto Project components used on a specific Toradex LTS release.
Those updates are provided as long as the respective version of the components still receive updates. They are typically maintained for 2 - 3 years and are subject to each component’s release plan.
Toradex uses Longterm/Stable Linux kernels for its own LTS releases whenever possible. It ensures that Toradex LTS releases receive kernel updates for an extended period of time.
Your linux repo mentioned has 4.4.291 yes you are right.
But BSP2.8, when I attempt to compile (but failed), I saw in the yocto log, it tries to compile v4.4.217 which is not the latest one available in the repo.
Are you certain about that v4.4.291 is used in the BSP2.8 and fully tested for vf50?
I think that the reference needs to be updated in layers/meta-toradex-nxp/recipes-kernel/linux/linux-toradex_4.4.bbappend
Not in linux-toradex_4.4.bb directly since it is overwritten by the bbappend file.
After updating the reference in the bbappend file, I got another error while bitbaking the reference image: ERROR: Task (../layers/meta-toradex-bsp-common/recipes-kernel/backports/backports_5.4.bb:do_compile) failed with exit code '1'
But my question is again, is this image fully tested or not?
What kind of automated test system do you have for vf50?
For example, are you sure that with the kernel above, I2C is fully functional or not?