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

[Ananyev, Konstantin]

> -----Original Message-----
> From: Richardson, Bruce
> Sent: Monday, September 18, 2017 11:32 AM
> To: Thomas Monjalon <thomas at monjalon.net>
> Cc: Ananyev, Konstantin <konstantin.ananyev at intel.com>; stephen at networkplumber.org; dev at dpdk.org; Shahaf Shuler
> <shahafs at mellanox.com>
> Subject: Re: [dpdk-dev] [PATCH 4/4] ethdev: add helpers to move to the new offloads API
> 
> On Thu, Sep 14, 2017 at 10:02:26AM +0200, Thomas Monjalon wrote:
> > 13/09/2017 23:42, Ananyev, Konstantin:
> > > From: Thomas Monjalon [mailto:thomas at monjalon.net]
> > > > 13/09/2017 14:56, Ananyev, Konstantin:
> > > > > From: Thomas Monjalon [mailto:thomas at monjalon.net]
> > > > Konstantin, I would like your opinion about the proposal below.
> > > > It is about making on the fly configuration more generic.
> > > > You say it is possible to configure VLAN on the fly,
> > > > and I think we should make it possible for other offload features.
> > >
> > > It would be a good thing, but I don't think it is possible for all offloads.
> > > For some of them you still have to stop the queue(port) first.
> > >
> > > Also I am not sure what exactly do you propose?
> > > Is that something like that:
> > > - wipe existing offload bitfileds from rte_eth_rxmode (already done by Shahaf)
> > > - Instead of uint64_t offloads inside both  rte_eth_rxmode and te_eth_rxconf
> > >   Introduce new functions:
> > >
> > > int rte_eth_set_port_rx_offload(portid, uint64_t offload_mask);
> > > int rte_eth_set_queue_rx_offload(portid, queueid, uint64_t offload_mask);
> Would be useful to have a valid mask here, to indicate what bits to use.
> That way, you can adjust one bit without worrying about what other bits
> you may change in the process. There are probably apps out there that
> just want to toggle a single bit on, and off, at runtime while ignoring
> others.
> Alternatively, we can have set/unset functions which enable/disable
> offloads, based on the mask.

My thought was  that people would do:

uint64_t offload = rte_eth_get_port_rx_offload(port);
offload |= RX_OFFLOAD_X;
offload &= ~RX_OFFLOAD_Y;
rte_eth_set_port_rx_offload(port, offload);

In that case, I think we don't really need a mask.

> 
> > >
> > > uint64_t rte_eth_get_port_rx_offload(portid);
> > > uint64_t rte_eth_set_queue_rx_offload(portid, queueid);
> s/set/get/
> > >
> > > And add new fileds:
> > > rx_offload_port_dynamic_capa
> > > rx_offload_queue_dynamic_capa
> > > inside rte_eth_dev_info.
> > >
> > > And it would be user responsibility to call set_port/queue_rx_offload()
> > > somewhere before dev_start() for static offloads.
> > > ?
> >
> > Yes exactly.
> >
> > > If so, then it seems reasonable to me.
> >
> > Good, thank you
> >
> >
> Sorry I'm a bit late to the review, but the above suggestion of separate
> APIs for enabling offloads, seems much better than passing in the flags
> in structures to the existing calls. From what I see all later revisions
> of this patchset still use the existing flags parameter to setup calls
> method.
> 
> Some advantages that I see of the separate APIs:
> * allows some settings to be set before start, and others afterwards,
>   with an appropriate return value if dynamic config not supported.
> * we can get fine grained error reporting from these - the set calls can
>   all return the mask indicating what offloads could not be applied -
>   zero means all ok, 1 means a problem with that setting. This may be
>   easier for the app to use than feature discovery in some cases.
> * for those PMDs which support configuration at a per-queue level, it
>   can allow the user to specify the per-port settings as a default, and
>   then override that value at the queue level, if you just want one queue
>   different from the rest.

I think we all in favor to have a separate API here.
Though from the discussion we had at latest TB, I am not sure it is doable
in 17.11 timeframe.
Konstantin