Re: [dpdk-dev] [RFC PATCH 4/4] ethdev: add helpers to move to the new offloads API

[Thomas Monjalon <thomas@monjalon.net>]

23/08/2017 15:13, Shahaf Shuler:
> Wednesday, August 23, 2017 3:29 PM, Ananyev, Konstantin:
> > From: Shahaf Shuler
> > > In order to enable PMDs to support only one of the APIs, and
> > > applications to avoid branching according to the underlying device a
> > > copy functions to/from the old/new APIs were added.

Looks a good intent.
I would prefer the word "convert" instead of "copy".

> > >  int
> > >  rte_eth_rx_queue_setup(uint8_t port_id, uint16_t rx_queue_id,
[...]
> > > +	} else if ((!(dev->data->dev_flags & RTE_ETH_DEV_RXQ_OFFLOAD)) &&
> > > +		   (dev->data->dev_conf.rxmode.ignore == 1)) {
> > > +		int ret;
> > > +		struct rte_eth_rxmode rxmode;
> > > +
> > > +		rte_eth_copy_rxq_offloads(&rxmode, rx_conf);
> > > +		if (memcmp(&rxmode, &dev->data->dev_conf.rxmode,
> > > +			   sizeof(rxmode))) {
> > > +			/*
> > > +			 * device which work with rxmode offloads API requires
> > > +			 * a re-configuration in order to apply the new offloads
> > > +			 * configuration.
> > > +			 */
> > > +			dev->data->dev_conf.rxmode = rxmode;
> > > +			ret = rte_eth_dev_configure(port_id,
> > > +					dev->data->nb_rx_queues,
> > > +					dev->data->nb_tx_queues,
> > > +					&dev->data->dev_conf);
> > 
> > Hmm, and why we would need to reconfigure our device in the middle of rx
> > queue setup?
> 
> The reason is the old Rx offloads API is configured on device configure. 
> This if section is for applications which already moved to the new offload
> API however the underlying PMD still uses the old one.

Isn't it risky to re-run configure here?
We could also declare this case as an error.

I think applications which have migrated to the new API,
could use the convert functions themselves before calling configure
to support not migrated PMDs.
The cons of my solution are:
- discourage apps to migrate before all PMDs have migrated
- expose a temporary function to convert API
I propose it anyway because there is always someone to like bad ideas ;)