nixos/uboot-builder: enable uboot support for rpi4

[c0deaddict]

Description of changes

I've been running NixOS with this patch on my Raspberry Pi 4 for almost a year now, it works fine.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.11 Release Notes (or backporting 23.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[samueldr]

All options to manage the platform firmware for the Raspberry Pi have been formally deprecated a few months back.

These options, including the U-Boot management options, may not work as expected for the default expected settings.

These files:

• nixpkgs/nixos/modules/system/boot/loader/raspberrypi/uboot-builder.sh

  Lines 22 to 38 in 78c07ab

  	# Add the firmware files
  	fwdir=@firmware@/share/raspberrypi/boot/
  	copyForced $fwdir/bootcode.bin $target/bootcode.bin
  	copyForced $fwdir/fixup.dat $target/fixup.dat
  	copyForced $fwdir/fixup_cd.dat $target/fixup_cd.dat
  	copyForced $fwdir/fixup_db.dat $target/fixup_db.dat
  	copyForced $fwdir/fixup_x.dat $target/fixup_x.dat
  	copyForced $fwdir/start.elf $target/start.elf
  	copyForced $fwdir/start_cd.elf $target/start_cd.elf
  	copyForced $fwdir/start_db.elf $target/start_db.elf
  	copyForced $fwdir/start_x.elf $target/start_x.elf
  	# Add the uboot file
  	copyForced @uboot@/u-boot.bin $target/u-boot-rpi.bin
  	# Add the config.txt
  	copyForced @configTxt@ $target/config.txt

Will be installed to the same location as these files:

• nixpkgs/nixos/modules/system/boot/loader/raspberrypi/uboot-builder.sh

  Lines 19 to 20 in 78c07ab

  	# Call the extlinux builder
  	"@extlinuxConfBuilder@" "$@"

This most likely does not do what people expect. For this to work "correctly", you have to have a setup where the platform firmware partition is mounted at /boot on the Raspberry Pi, which is not a recommended, and is not a supported configuration.

[c0deaddict]

All options to manage the platform firmware for the Raspberry Pi have been formally deprecated a few months back.

These options, including the U-Boot management options, may not work as expected for the default expected settings.

These files:

* https://github.com/NixOS/nixpkgs/blob/78c07ab688cde97d6705d9507ccbc99a2001d970/nixos/modules/system/boot/loader/raspberrypi/uboot-builder.sh#L22-L38

Will be installed to the same location as these files:

* https://github.com/NixOS/nixpkgs/blob/78c07ab688cde97d6705d9507ccbc99a2001d970/nixos/modules/system/boot/loader/raspberrypi/uboot-builder.sh#L19-L20

This most likely does not do what people expect. For this to work "correctly", you have to have a setup where the platform firmware partition is mounted at /boot on the Raspberry Pi, which is not a recommended, and is not a supported configuration.

Aha, I have missed that deprecation warning then :) So if I understand correctly: on a Pi4 there is no need anymore to set boot.loader.raspberryPi.uboot.enable = true? NixOS will always configure uboot by default on Pi's?

[samueldr]

boot.loader.raspberryPi.uboot.enable hasn't been needed and hasn't "worked" as expected on NixOS ARM images on any image generated since mid-2019.

The current expectation is to enable the boot.loader.generic-extlinux-compatible options on all U-Boot using ARM systems, which includes the Raspberry Pi.