crypto: doc - document crypto engine API

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CRYPTO ENGINE

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Overview

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The crypto engine API (CE), is a crypto queue manager.

Requirement

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You have to put at start of your tfm_ctx the struct crypto_engine_ctx

struct your_tfm_ctx {

        struct crypto_engine_ctx enginectx;

        ...

};

Why: Since CE manage only crypto_async_request, it cannot know the underlying

request_type and so have access only on the TFM.

So using container_of for accessing __ctx is impossible.

Furthermore, the crypto engine cannot know the "struct your_tfm_ctx",

so it must assume that crypto_engine_ctx is at start of it.

Order of operations

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You have to obtain a struct crypto_engine via crypto_engine_alloc_init().

And start it via crypto_engine_start().

Before transferring any request, you have to fill the enginectx.

- prepare_request: (taking a function pointer) If you need to do some processing before doing the request

- unprepare_request: (taking a function pointer) Undoing what's done in prepare_request

- do_one_request: (taking a function pointer) Do encryption for current request

Note: that those three functions get the crypto_async_request associated with the received request.

So your need to get the original request via container_of(areq, struct yourrequesttype_request, base);

When your driver receive a crypto_request, you have to transfer it to

the cryptoengine via one of:

- crypto_transfer_ablkcipher_request_to_engine()

- crypto_transfer_aead_request_to_engine()

- crypto_transfer_akcipher_request_to_engine()

- crypto_transfer_hash_request_to_engine()

- crypto_transfer_skcipher_request_to_engine()

At the end of the request process, a call to one of the following function is needed:

- crypto_finalize_ablkcipher_request

- crypto_finalize_aead_request

- crypto_finalize_akcipher_request

- crypto_finalize_hash_request

- crypto_finalize_skcipher_request