{ lib
, common_amd64
}:

{
  overlays = common_amd64.overlays ++ [(final: prev:
    let
      fmap-size-in-bytes = 1024;
      flash-chip-bytes-per-image = final.flash-chip-size-in-bytes / final.images-per-flash-chip;
      cbfs-size-in-bytes = flash-chip-bytes-per-image - fmap-size-in-bytes;
      fallback-image-address-in-bytes =
        if final.images-per-flash-chip <= 1
        then 0
        else flash-chip-bytes-per-image;
    in {

    platform_name = "am1i";

    kernel =
      final.lib.makeOverridable (prev.kernel.override {
        config = ./linux.config;
        buildTargets = [ "bzImage" ];
      }).overrideAttrs (a: {
        postInstall = (a.postInstall or "") + ''
          cp arch/x86_64/boot/bzImage $out/
        '';
      });

    console-device = "ttyS1";
    payload = "${final.kernel}/bzImage";
    fmap = final.nixpkgsOnBuildForBuild.writeText "custom.fmap" (''
      #
      # Note: on x86 platforms the SPI flash is mapped into or copied into
      # the topmost X bytes of memory, and the very topmost word of memory
      # is the "reset vector" which points to the BIOS entry point.  Because
      # of this we must protect the TOPMOST half of memory; if an attacker
      # controls the reset vector and any other chunk of the flash, the game
      # is over.
      #
      FLASH@0 0x${lib.toHexString final.flash-chip-size-in-bytes} {
        BIOS@0 0x${lib.toHexString final.flash-chip-size-in-bytes} {
    '' + lib.optionalString (final.images-per-flash-chip > 1) ''
          # read-write zone
          NORMAL(CBFS)   @    0x${lib.toHexString fmap-size-in-bytes} 0x${lib.toHexString cbfs-size-in-bytes}
    '' + ''

    '' + lib.optionalString (final.images-per-flash-chip > 1) ''
          # read-only zone (eventually)
          FMAP           @ 0x${lib.toHexString flash-chip-bytes-per-image}    0x${lib.toHexString fmap-size-in-bytes}
          FALLBACK(CBFS) @ 0x${lib.toHexString (flash-chip-bytes-per-image + fmap-size-in-bytes)} 0x${lib.toHexString cbfs-size-in-bytes}
    '' + ''
        }
      }
    '');

    coreboot = (prev.coreboot.override {
      iasl = final.iasl_20180531;
      coreboot-toolchain = with final.coreboot-toolchain; [ x64 i386 ];
      config = with lib.kernel; {
        CBFS_PREFIX = lib.mkForce (freeform "prefix");

        VENDOR_ASUS = lib.mkForce yes;
        BOARD_ASUS_AM1I_A = lib.mkForce yes;

        CONSOLE_CBMEM = lib.mkForce no;
        DRIVERS_INTEL_WIFI = lib.mkForce no;
        HUDSON_XHCI_ENABLE = lib.mkForce no;
        ON_DEVICE_ROM_LOAD = lib.mkForce no;
        POST_DEVICE = lib.mkForce no;
        POST_IO = lib.mkForce no;

        DEFAULT_CONSOLE_LOGLEVEL = lib.mkForce (freeform "7");
        ONBOARD_VGA_IS_PRIMARY = lib.mkForce yes;

        MAINBOARD_SMBIOS_MANUFACTURER = lib.mkForce (freeform "ASUS");
        MAINBOARD_SMBIOS_PRODUCT_NAME = lib.mkForce (freeform "AM1I-A");
      };
      uart-for-console =
        if      final.console-device == "ttyS0" then 0 # IDC ribbon-cable header on the motherboarod
        else if final.console-device == "ttyS1" then 1 # DB9 connector on rear I/O panel; omitted from some board variants
        else if final.console-device == null then null
        else throw "am1i currently supports only `null` and `ttyS{0,1}` for `console-device`";
    }).overrideAttrs (a: {
      postInstall = (a.postInstall or "") + ''
        cp src/mainboard/asus/am1i-a/cmos.layout $out/
      '';
    });
  })];
}