Split the T400 bootloader into self-contained, importable modules so the host
can match whatever firmware is flashed (switch by changing one import):
- boot-bios.nix stock BIOS / coreboot+SeaBIOS -> GRUB on the MBR (default)
- boot-coreboot-grub.nix coreboot GRUB payload -> config-only GRUB (device=nodev)
- boot-coreboot-uefi.nix coreboot Tianocore/UEFI payload -> systemd-boot; carries
its own ESP (/boot vfat) so it travels with the mode
Cover the optional discrete ATI Mobility Radeon HD 3470 (RV620): load the open
`radeon` KMS driver in the initrd for early modesetting (firmware via
enableRedistributableFirmware), with a note on the T400's switchable graphics.
All three boot variants evaluate; nixfmt clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Emma Thorpe
b3fa34f431