Kernel caching in README

[nbrr]

This bit of the README was removed, yet the current README still references to it.

  nixConfig = {
    extra-substituters = [ "https://raspberry-pi-nix.cachix.org" ];
    extra-trusted-public-keys = [
      "raspberry-pi-nix.cachix.org-1:WmV2rdSangxW0rZjY/tBvBDSaNFQ3DyEQsVw8EvHn9o="
    ];
  };

What is the current way of benefiting from a cache?

FWIW this seems to be doing fine:

    extra-substituters = [ "https://nix-community.cachix.org" ];
    extra-trusted-public-keys = [
      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
    ];

[tstat]

Oh yes, that's a mistake. The nix-community cache is the current cache.

[tobiasBora]

Do we still need kernel caching now that rpi5 is in nixpkgs ? https://github.com/NixOS/nixos-hardware/pull/927

[mroi]

@tobiasBora The PR your referenced seems to add rpi5 support to nixos-hardware, not Nixpkgs. Is there some automatic process by which this addition would move into Nixpkgs?

[tstat]

@tobiasBora as things are written we do, since we have our own derivation of the rpi linux fork. I assume you are more getting at "can we avoid defining a kernel derivation in this repo now", and yes, we probably could. I don't really think we should though. I like being able to bump the dep more aggressively, have control over things like the kernel config and patches, etc.

[tobiasBora]

Ok thanks for your answer @tstat ! Regarding @mroi 's question, you are right, I actually realized that it is in nixos hardware, not nixpkgs directly… hence it is not cached by Hydra itself, sorry.

[mroi]

Got it. Thanks to you both for the clarification.