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+.. SPDX-License-Identifier: GPL-2.0
+
+Crypto Engine
+=============
+
+Overview
+--------
+The crypto engine (CE) API is a crypto queue manager.
+
+Requirement
+-----------
+You must put, at the start of your transform context your_tfm_ctx, the structure
+crypto_engine:
+
+::
+
+	struct your_tfm_ctx {
+		struct crypto_engine engine;
+		...
+	};
+
+The crypto engine only manages asynchronous requests in the form of
+crypto_async_request. It cannot know the underlying request type and thus only
+has access to the transform structure. It is not possible to access the context
+using container_of. In addition, the engine knows nothing about your
+structure "``struct your_tfm_ctx``". The engine assumes (requires) the placement
+of the known member ``struct crypto_engine`` at the beginning.
+
+Order of operations
+-------------------
+You are required to obtain a struct crypto_engine via ``crypto_engine_alloc_init()``.
+Start it via ``crypto_engine_start()``. When finished with your work, shut down the
+engine using ``crypto_engine_stop()`` and destroy the engine with
+``crypto_engine_exit()``.
+
+Before transferring any request, you have to fill the context enginectx by
+providing functions for the following:
+
+* ``prepare_crypt_hardware``: Called once before any prepare functions are
+  called.
+
+* ``unprepare_crypt_hardware``: Called once after all unprepare functions have
+  been called.
+
+* ``prepare_cipher_request``/``prepare_hash_request``: Called before each
+  corresponding request is performed. If some processing or other preparatory
+  work is required, do it here.
+
+* ``unprepare_cipher_request``/``unprepare_hash_request``: Called after each
+  request is handled. Clean up / undo what was done in the prepare function.
+
+* ``cipher_one_request``/``hash_one_request``: Handle the current request by
+  performing the operation.
+
+Note that these functions access the crypto_async_request structure
+associated with the received request. You are able to retrieve the original
+request by using:
+
+::
+
+	container_of(areq, struct yourrequesttype_request, base);
+
+When your driver receives a crypto_request, you must to transfer it to
+the crypto engine via one of:
+
+* crypto_transfer_aead_request_to_engine()
+
+* crypto_transfer_akcipher_request_to_engine()
+
+* crypto_transfer_hash_request_to_engine()
+
+* crypto_transfer_kpp_request_to_engine()
+
+* crypto_transfer_skcipher_request_to_engine()
+
+At the end of the request process, a call to one of the following functions is needed:
+
+* crypto_finalize_aead_request()
+
+* crypto_finalize_akcipher_request()
+
+* crypto_finalize_hash_request()
+
+* crypto_finalize_kpp_request()
+
+* crypto_finalize_skcipher_request()