Re: eventdev: rte_event_dev_start() all queues are linked requirement

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Mon, 30 Jul 2018 07:38:27 +0000
> From: "Elo, Matias (Nokia - FI/Espoo)" <matias.elo@nokia.com>
> To: "dev@dpdk.org" <dev@dpdk.org>
> CC: "jerin.jacob@caviumnetworks.com" <jerin.jacob@caviumnetworks.com>, "Van
>  Haaren, Harry" <harry.van.haaren@intel.com>
> Subject: eventdev: rte_event_dev_start() all queues are linked requirement
> x-mailer: Apple Mail (2.3445.9.1)
> 

+ mattias.ronnblom@ericsson.com as his SW driver is scheduled for next
release.

> 
> Hi,
> 
> rte_event_dev_start() requires that all queues have to be linked, which makes
> writing applications which link/unlink queues at runtime cumbersome.
> E.g. the application has to dummy link all queues before rte_event_dev_start()
> and then unlink them after the function call. This alone wouldn't be a big issue
> but rte_event_dev_start() may also be called inside
> rte_event_eth_rx_adapter_create() implementation causing additional complexity.
> 
> To me this check seems more like eventdev implementation specific limitation,
> which should be solved by the particular implementation and not enforced by the
> API to all applications. From an application point of view enqueueing events to
> an unlinked queue and expecting something meaningful to happen is an error
> anyway. So, would it be conceivable to remove this particular requirement?

For HW drivers, It is OK remove the particular requirement. But, If
there is an issue(performance/functionality) for enabling such feature
in SW driver. I would like keep that constraint to keep eventdev as
abstraction for both SW and HW driver. Harry and/or Mattias.ronnblom can
comment from SW driver perspective.

> 
> -Matias