Re: [yocto] How to switch between package version ?

[Mikko Rapeli <mikko.rapeli@linaro.org>]

Hi,

On Wed, Aug 16, 2023 at 05:32:23PM +0200, Alexander Kanavin wrote:
> On Wed, 16 Aug 2023 at 14:05, Mikko Rapeli <mikko.rapeli@linaro.org> wrote:
> > There isn't much documentation. It's more about just doing it and resolving any issues
> > you find. For example BSP deliveries from vendors frequently only support older yocto branches.
> > These should not dictate the poky release for the full SW stack when for example only kernel
> > and bootloader are needed from their delivery. Thus using older BSP layer with the kernel
> > and other recipes with a newer poky is a matter of configuring the build system and resolving
> > any build failures from e.g. newer poky and gcc. The layer compatibility setting meant to warn
> > and prohibit from doing this, but this can be overruled in other layers by setting
> > e.g. LAYERSERIES_COMPAT_security-layer += "mickledore kirkstone" in layer.conf of your own
> > layers. If large parts of a layer (BSP) are not needed in your configuration and cause
> > build issues, then those can be hidden by setting BBMASK for those paths.
> 
> Mikko, please. Yes, you can work around all these restrictions with
> some determination, but they exist for good reasons. So can you avoid
> giving newcomers bad advice, and instead dig into the actual problem
> they have? Pretty please.

One of the major problems with yocto major updates is that it becomes a big bang,
everything must be updated at once. This can be split down and individual layers updated
one at a time while keeping poky on the old version. This requires working around
layer compatibility, which in many cases is quite artificial and just indiciates that layer
is not tested with the other poky versions but it might still just work.

I've done this so many times now that I don't see any reason to hide it,
also because many non-core layers are simply not maintaining other than master branch
exposing users to obsole and insecure SW if they stick to the branch name.

Cheers,

-Mikko