add documents

lib/openflow/actions/dec_nw_ttl.ex

@@ -1,21 +1,35 @@
 defmodule Openflow.Action.DecNwTtl do
   @moduledoc """
+  Decrement IP TTL
   """
 
   defstruct([])
 
   alias __MODULE__
 
+  @type t :: %DecNwTtl{}
+
+  @spec ofpat() :: 24
   def ofpat, do: 24
 
+  @doc """
+  Create a new dec_nw_ttl action struct
+
+  ```elixir
+  iex> %DecNwTtl{} = DecNwTtl.new()
+  ```
+  """
+  @spec new() :: t()
   def new do
     %DecNwTtl{}
   end
 
+  @spec to_binary(t()) :: <<_::16, _::_*8>>
   def to_binary(%DecNwTtl{}) do
     <<24::16, 8::16, 0::size(4)-unit(8)>>
   end
 
+  @spec read(<<_::16, _::_*8>>) :: t()
   def read(<<24::16, 8::16, _::size(4)-unit(8)>>) do
     %DecNwTtl{}
   end