Comment 8 for bug 1846329

After much review discussion I am sponsoring 2019.07+dfsg-1ubuntu4 to Focal and 2019.07+dfsg-1ubuntu3~18.04.1 to Bionic (I tweaked the version).

On the Bionic backport, I note that it's essentially impossible to review all the upstream changes for functional behaviour changes to users on Bionic, so we will have to rely entirely on QA instead. The alternative is to not enable Pi 4 on Bionic at all, so on balance this seems like the only reasonable path forward.

Eoan needs looking at. Some changes from 2019.07+dfsg-1ubuntu3 to 2019.07+dfsg-1ubuntu4 may need backporting in an SRU to Eoan to make sure the upgrade path Bionic->Eoan->Focal works correctly at both of those points. I suggest this needs resolving before the Bionic SRU lands in the updates pocket, but leave that decision to the SRU reviewer.

We also identified a race condition: if flash-kernel is deconfigured to resolve the Breaks and then upgraded afterwards, flash-kernel won't run itself. This will be fixed separately in flash-kernel and will need no further changes to u-boot.