     System.get_env(var_name) || raise_env_var_missing(var_name)
   end
 
-  def get_devs do
+  defp get_devs do
     {result, 0} =
       if WSL.running_on_wsl?() do
         WSL.get_fwup_devices()

          end

        case Enum.fetch(devs, idx) do
          {:ok, [dev, _]} -> dev
          _ -> Mix.raise("Invalid selection #{choice}")
        end
    end

    result
    |> String.trim()
    |> String.split("\n")
    |> Enum.map(&parse_dev/1)
  end

  defp parse_dev(line) do
    [dev, bytes | _rest] = String.split(line, ",")
    {dev, bytes}
  end

  def prompt_dev() do
    case get_devs() do
      [{dev, bytes}] ->
        choice =
          Mix.shell().yes?("Use #{bytes_to_gigabytes(bytes)} GiB memory card found at #{dev}?")

