xref: /kernel/linux/linux-6.6/Documentation/crypto/crypto_engine.rst (revision 62306a36)

.. 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()