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+..  SPDX-License-Identifier: BSD-3-Clause
+    Copyright(c) 2016 Intel Corporation.
+
+Null Crypto Poll Mode Driver
+============================
+
+The Null Crypto PMD (**librte_pmd_null_crypto**) provides a crypto poll mode
+driver which provides a minimal implementation for a software crypto device. As
+a null device it does not modify the data in the mbuf on which the crypto
+operation is to operate and it only has support for a single cipher and
+authentication algorithm.
+
+When a burst of mbufs is submitted to a Null Crypto PMD for processing then
+each mbuf in the burst will be enqueued in an internal buffer for collection on
+a dequeue call as long as the mbuf has a valid rte_mbuf_offload operation with
+a valid rte_cryptodev_session or rte_crypto_xform chain of operations.
+
+Features
+--------
+
+Modes:
+
+* RTE_CRYPTO_XFORM_CIPHER ONLY
+* RTE_CRYPTO_XFORM_AUTH ONLY
+* RTE_CRYPTO_XFORM_CIPHER THEN RTE_CRYPTO_XFORM_AUTH
+* RTE_CRYPTO_XFORM_AUTH THEN RTE_CRYPTO_XFORM_CIPHER
+
+Cipher algorithms:
+
+* RTE_CRYPTO_CIPHER_NULL
+
+Authentication algorithms:
+
+* RTE_CRYPTO_AUTH_NULL
+
+Limitations
+-----------
+
+* Only in-place is currently supported (destination address is the same as
+  source address).
+
+Installation
+------------
+
+The Null Crypto PMD is enabled and built by default in both the Linux and
+FreeBSD builds.
+
+Initialization
+--------------
+
+To use the PMD in an application, user must:
+
+* Call rte_vdev_init("crypto_null") within the application.
+
+* Use --vdev="crypto_null" in the EAL options, which will call rte_vdev_init() internally.
+
+The following parameters (all optional) can be provided in the previous two calls:
+
+* socket_id: Specify the socket where the memory for the device is going to be allocated
+  (by default, socket_id will be the socket where the core that is creating the PMD is running on).
+
+* max_nb_queue_pairs: Specify the maximum number of queue pairs in the device (8 by default).
+
+* max_nb_sessions: Specify the maximum number of sessions that can be created (2048 by default).
+
+Example:
+
+.. code-block:: console
+
+    ./l2fwd-crypto -l 1 -n 4 --vdev="crypto_null,socket_id=0,max_nb_sessions=128" \
+    -- -p 1 --cdev SW --chain CIPHER_ONLY --cipher_algo "null"