[dpdk-dev] [PATCH v2 1/2] net/fm10k: convert to new Rx offloads API

[Ananyev, Konstantin]

Hi Qi,

> > > > > >
> > > > > > Hi Daiwei:
> > > > > >
> > > > > > > +static uint64_t fm10k_get_rx_queue_offloads_capa(struct
> > > > > > > +rte_eth_dev
> > > > > > > +*dev) {
> > > > > > > +	RTE_SET_USED(dev);
> > > > > > > +
> > > > > > > +	return (uint64_t)(DEV_RX_OFFLOAD_SCATTER);
> > > > > > > +}
> > > > > >
> > > > > > why per queue rx scattered feature here?
> > > > > > My understanding is either we use scattered rx function that
> > > > > > enable this feature for all queues or we use non-scattered rx
> > > > > > function that disable this feature for all queues, right?
> > > > >
> > > > > Checked with Dai Wei offline, fm10k have per queue register that
> > > > > can be configured to support rx scattered, So it is per queue offload.
> > > >
> > > > Ok, but these days we have one RX function per device.
> > > > Looking at fm10k - it clearly has different RX function for
> > > > scattered and non-scattered case.
> > > > Yes, HW does support scatter/non-scatter selection per queue, but
> > > > our SW - doesn't (same for ixgbe and i40e) So how it could be per queue
> > offload?
> > >
> > > We saw the implementation of fm10k is a little bit different with i40e.
> > > It set per queue register "FM10K_SRRCTL_BUFFER_CHAINING_EN" to turn
> > on multi-seg feature when offload is required.
> > >
> > > That means two queues can have different behavior when process a
> > > packet that exceed the buffer size base on the register setting, though we
> > use the same rx scattered function, so we think this is per queue feature, is
> > that make sense?
> >
> > Ok, suppose we have 2 functions configured.
> > One with DEV_RX_OFFLOAD_SCATTER is on, second with
> > DEV_RX_OFFLOAD_SCATTER is off.
> > So scatter RX function will be selected, but for second queue  HW support
> > will not be enabled, so packets bigger then RX buffer will be silently dropped
> > by HW, right?
> 
> Yes according to datasheet
> 
> Bit FM10K_SRRCTL_BUFFER_CHAINING_EN:
> 
> 0b = Any packet longer than the data buffer size is terminated with a
> TOO_BIG error status in Rx descriptor write-back. The remainder of the
> frame is not posted to host, it is silently dropped.
> 1b = A packet can be spread over more than one single receive data buffer
> 

Ok, that's a bit unusual approach but understandable.
Thanks
Konstantin