platform.nix

  {
    name = "armv7l-hf-multiplatform-custom";
    kernelMajor = "2.6"; # Using "2.6" enables 2.6 kernel syscalls in glibc.
    kernelHeadersBaseConfig = "multi_v7_defconfig";
    kernelBaseConfig = "multi_v7_defconfig";
    kernelArch = "arm";
    kernelDTB = true;
    kernelAutoModules = false;
    uboot = null;
    kernelTarget = "zImage";
    kernelExtraConfig = ''
      AHCI_IMX y
      CONFIG_RTC_DRV_S3C n
    '';
    gcc = {
      # Some table about fpu flags:
      # http://community.arm.com/servlet/JiveServlet/showImage/38-1981-3827/blogentry-103749-004812900+1365712953_thumb.png
      # Cortex-A5: -mfpu=neon-fp16
      # Cortex-A7 (rpi2): -mfpu=neon-vfpv4
      # Cortex-A8 (beaglebone): -mfpu=neon
      # Cortex-A9: -mfpu=neon-fp16
      # Cortex-A15: -mfpu=neon-vfpv4

      # More about FPU:
      # https://wiki.debian.org/ArmHardFloatPort/VfpComparison

      # vfpv3-d16 is what Debian uses and seems to be the best compromise: NEON is not supported in e.g. Scaleway or Tegra 2,
      # and the above page suggests NEON is only an improvement with hand-written assembly.
      arch = "armv7-a";
      fpu = "vfpv3-d16";
      float = "hard";

      # For Raspberry Pi the 2 the best would be:
      #   cpu = "cortex-a7";
      #   fpu = "neon-vfpv4";
    };
  }