Re: [dpdk-dev] [PATCH v5 4/7] ethdev: copy fast-path API into separate structure

From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: fengchengwen <fengchengwen@huawei.com>, "dev@dpdk.org" <dev@dpdk.org>
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Subject: Re: [dpdk-dev] [PATCH v5 4/7] ethdev: copy fast-path API into separate structure
Date: Mon, 11 Oct 2021 15:24:08 +0000	[thread overview]
Message-ID: <DM6PR11MB449192F148F2A4139103B8DD9AB59@DM6PR11MB4491.namprd11.prod.outlook.com> (raw)
In-Reply-To: <2f8c4eba-879f-7ee8-28c3-f8c23f1f885d@huawei.com>

> 
> Sorry to self-reply.
> 
> I think it's better the 'struct rte_eth_dev *dev' hold a pointer to the
> 'struct rte_eth_fp_ops', e.g.
> 
> 	struct rte_eth_dev {
> 		struct rte_eth_fp_ops *fp_ops;
> 		...  // other field
> 	}
> 
> The eth framework set the pointer in the rte_eth_dev_pci_allocate(), and driver fill
> corresponding callback:
> 	dev->fp_ops->rx_pkt_burst = xxx_recv_pkts;
> 	dev->fp_ops->tx_pkt_burst = xxx_xmit_pkts;
> 	...
> 
> In this way, the behavior of the primary and secondary processes can be unified, which
> is basically the same as that of the original process.

I don't think it is a good thing to do, as it nullifies one of the main thing of this approach:
fp_ops[] points to actual rx/tx functions and data only when PMD is really ready to do rx/tx
(device is properly configured and started), in other cases it points to dummy stubs.
As another drawback it will mean code changes in aach and every driver.