document MAX_LENGTH
diff --git a/docs/hazmat/primitives/asymmetric/padding.rst b/docs/hazmat/primitives/asymmetric/padding.rst
index 632f698..8a03432 100644
--- a/docs/hazmat/primitives/asymmetric/padding.rst
+++ b/docs/hazmat/primitives/asymmetric/padding.rst
@@ -34,5 +34,10 @@
:param int salt_length: The length of the salt. It is recommended that this
be set to ``MGF1.MAX_LENGTH``.
+ .. attribute:: MAX_LENGTH
+
+ Pass this attribute to ``salt_length`` to get the maximum salt length
+ available.
+
.. _`Padding is critical`: http://rdist.root.org/2009/10/06/why-rsa-encryption-padding-is-critical/