The ablkcipher_request data structure contains all pointers to data required for the asynchronous cipher operation. This includes the cipher handle (which can be used by multiple ablkcipher_request instances), pointer to plaintext and ciphertext, asynchronous callback function, etc. It acts as a handle to the ablkcipher_request_* API calls in a similar way as ablkcipher handle to the crypto_ablkcipher_* API calls.