Asynchronous operation utilizes the OpenSSL* asynchronous mode (ASYNC_JOB
infrastructure) introduced in OpenSSL* version 1.1.0. In the
OpenSSL* master branch this infrastructure was augmented to provide an
additional callback method by which the OpenSSL* Engine can be notified
of crypto operation request completions by the hardware accelerator. This
additional method can be used if you think that using the alternative
file descriptor method descriptor is too costly in terms of CPU cycles
or in some context where a file descriptor is not appropriate.
The QAT OpenSSL* Engine build system will automatically detect whether the
OpenSSL* version being built against supports this additional callback method.
If so, the QAT OpenSSL* Engine code will use the callback
mechanism for job completion rather than the file descriptor
mechanism if a callback function has been set. If a callback has not
been set then the file descriptor method will be used.
For further details on using the OpenSSL* asynchronous mode infrastructure please see the OpenSSL* online documentation located at: