Define a kernel policy

[JamieMagee]

I touched on this a little bit in my recent kernel update PRs (#101 and #102), but this repository doesn't have a policy about which kernels are defined in flake.nix. Currently we have:

• 6.6.51
• 6.6.67
• 6.10.12

I think a good policy might be something like:

• Latest stable_* tag
• Latest LTS kernel release
  • Currently rpi-6.12.y
    • Either the tag rpi-6.12.y_20241206_2 which is 6.12.1
    • Or the tip of rpi-6.12.y which is currently 6.12.11
• Latest mainline kernel release
  • Currently rpi-6.13.y

[tstat]

Yes, good idea. I also think that's a good policy. I also think defaulting the the latest stable (as is done currently) is best.

[koalalorenzo]

It would be nice to have the latest stable and all the LTS versions (latest LTS and currently LTS supported: at the moment of writing that would be 6.6.x and 6.12.x).

[pta2002]

Why not mirror what NixOS does? https://wiki.nixos.org/wiki/Linux_kernel

• Default is latest LTS
• Also available will be:
  • For stable: latest kernel version at the time of stabilization
  • For unstable: latest kernel version

[JamieMagee]

Unfortunately, I don't think upstream NixOS policy maps as well onto the Raspberry Pi.

Setting the default kernel as the latest Linux LTS release would be 6.12.15, which is not tagged in raspberrypi/linux. Whereas the newest stable_ tag from raspberrypi/linux is currently stable_20250127 which is 6.6.74, and the latest published kernel for Raspberry Pi OS is 6.6.51¹ (AKA the stable_20241008 tag).

I'd advocate for tracking what is shipped to Raspberry Pi OS over the current Linux LTS version.

Footnotes

1. https://downloads.raspberrypi.com/raspios_arm64/release_notes.txt ↩

[pta2002]

Hadn't considered that, but it is a good point. Still, I think it makes sense to always provide whatever the latest release by rpi is, since it's not always necessarily the primary one they release. For instance they were on 6.6 officially for a good while but the patched sources for later versions were still available.