[dpdk-dev] rte_eth_from_rings

Sridhar Pitchai sridhar.pitchai at outlook.com
Fri Jan 27 23:31:52 CET 2017

Thanks Bruce.

I have created eth_dev from the rings as below.
rt = rte_eth_from_rings(port_p->name,
             (struct rte_ring * const*)port_p->rx_ring_p, 2,
                            (struct rte_ring * const*)port_p->tx_ring_p, 2,

Lets say I have a call back something like

        pkt_rx(void * pkt_p, struct pkt_metadata_t *meta_p)

which is called when there is a pkt at the chip.
inside this function(pkt_rx) i will find the port and the corresponding ring_p and
enqueue the pkt into the queue. I am assuming this should work. Kindly correct me if i misunderstood you.

question 2:
Can use this eth_dev to create KNI interface, like below.
rte_eth_dev_info_get(fp_p->port_list[port].key.port_id, &dev_info);
ops.port_id = fp_p->port_list[port].key.port_id;  // rt from rte_eth_from_rings(...)
                ops.change_mtu = _kni_ifconfig_mtu; // static function
                ops.config_network_if = _kni_ifconfig; // static functions
PORT(fp_p, port).kni_p = rte_kni_alloc(PORT(fp_p, port).mbuf_p,
                                                                &conf, &ops);

I am assuming this should work as well. I find the netdevs created but when i try to configure
them i am facing the following error.

root@ VM snaproute/softpath (master) >ifconfig PORT_8
PORT_8    Link encap:Ethernet  HWaddr be:35:c3:0f:f8:2f
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

root@ VM snaproute/softpath (master) >ifconfig PORT_8 up
SIOCSIFFLAGS: Timer expired
SIOCSIFFLAGS: Timer expired
root@ VM snaproute/softpath (master) >

Thanks for the help.

Sridhar Pitchai

From: Bruce Richardson <bruce.richardson at intel.com>
Sent: Friday, January 27, 2017 1:36 PM
To: Sridhar Pitchai
Cc: dev at dpdk.org
Subject: Re: [dpdk-dev] rte_eth_from_rings

On Fri, Jan 27, 2017 at 07:16:25PM +0000, Sridhar Pitchai wrote:
> Hi,
> I am trying to write a data path for packets punted to CPU(slowpath) from vender silicon like broadcom. I am planing to use "rte_eth_from_rings" like model where I will be able to read and write to the ring for the packets punted from vendor chip.
> the eth_dev abstraction provided by "rte_eth_from_rings" helps to build the dpdk data path. Can someone help me on how to read and write to the rings that is emulating the eth_dev.
To use the rings like an ethdev just use rte_eth_rx_burst and
rte_eth_tx_burst, passing in the port id of your newly created rings
ethdev. To access them directly as rings, just use the ring
enqueue/dequeue functions passing in the ring pointer as normal.


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