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From: kumaraparameshwaran rathinavel <kumaraparamesh92@gmail.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>
Cc: Thomas Monjalon <thomas@monjalon.net>,
	"Wiles, Keith" <keith.wiles@intel.com>,
	dev@dpdk.org,  Kumara Parameshwaran <kparameshwar@vmware.com>,
	Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>,
	 David Marchand <david.marchand@redhat.com>
Subject: Re: [PATCH] net/tap: Bug fix to populate fds in secondary process
Date: Tue, 18 Jan 2022 16:51:18 +0530
Message-ID: <CANxNyatvCNNC35idXfqSZekE-z6H2LCchXFCuzYKcCAhqEyBWw@mail.gmail.com> (raw)
In-Reply-To: <6aed79d2-be6c-7f30-a562-7acd69ebae57@intel.com>

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Just wanted to bring it to your attention,

In Mellanox driver there is a requirement to exchange fds between primary
and secondary and similar usage is seen, the primary sends the port_id and
the secondary refers to the rte_eth_devices in the driver,
The functions are
           - mlx5_mp_secondary_handle in secondary
           - mlx5_mp_req_start_rxtx in primary which is invoked from
mlx5_dev_start.

In my implementation I have used the name and invoked get_port_by_name, I
can also pass the port_id from the primary to make it uniform. So with
similar usage in Mellanox is there a problem there as well on referring to
the rte_eth_devices from the PMD ?


On Tue, Jan 18, 2022 at 3:17 PM Ferruh Yigit <ferruh.yigit@intel.com> wrote:

> On 1/17/2022 6:33 PM, Thomas Monjalon wrote:
> > 17/01/2022 19:28, Ferruh Yigit:
> >>> +   ret = rte_eth_dev_get_port_by_name(request_param->port_name,
> &port_id);
> >>> +   if (ret) {
> >>> +           TAP_LOG(ERR, "Failed to get port id for %s",
> >>> +                   request_param->port_name);
> >>> +           return -1;
> >>> +   }
> >>> +   dev = &rte_eth_devices[port_id];
> >>
> >> Since this is not really related with your patch, I want to have a
> separate thread for it.
> >>
> >> It is not good to access the 'rte_eth_devices' global variable directly
> from a driver, that
> >> is error prone.
> >>
> >> Btw, what 'peer' supposed to contain?
> >>
> >> It can be solved by adding an internal API, only for drivers to get
> eth_dev from the name,
> >> like: 'rte_eth_dev_get_by_name()'.
> >> This way a few other usage can be converted to this API.
> >>
> >> @Thomas and @Andrew what do you think about the new API proposal?
> >
> > It looks similar to rte_eth_dev_get_port_by_name() which returns a
> port_id.
>
> Exactly, but get eth_dev directly for drivers. For drivers no need to work
> with port_id
> handler, they can use eth_dev directly.
>
> Another solution can be an getter function for drivers, which gets port_id
> and returns
> the eth_dev.
>
> > It is a bit strange for an ethdev driver to not have access to its own
> ethdev struct.
> > Isn't there something broken in the logic?
> >
>
> This is callback function between primary and secondary applications sync.
> So port name
> will be same for both, but eth_dev will be different and port_id may be
> different.
> Driver finds its own eth_dev from the shared port name.
>
>

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  reply	other threads:[~2022-01-18 11:21 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-26  4:15 Kumara Parameshwaran
2022-01-17 18:22 ` Ferruh Yigit
2022-01-18  4:39   ` Kumara Parameshwaran
2022-01-18  9:10     ` Ferruh Yigit
2022-01-18 10:52       ` kumaraparameshwaran rathinavel
2022-01-18 12:14         ` Ferruh Yigit
2022-01-17 18:28 ` Ferruh Yigit
2022-01-17 18:33   ` Thomas Monjalon
2022-01-18  9:47     ` Ferruh Yigit
2022-01-18 11:21       ` kumaraparameshwaran rathinavel [this message]
2022-01-18 12:12         ` Ferruh Yigit
2022-01-18 12:31           ` Thomas Monjalon
2022-01-17 22:16 ` Stephen Hemminger
2022-01-18  5:22   ` Kumara Parameshwaran
2022-01-18 16:21     ` Stephen Hemminger
2022-01-19  4:33       ` kumaraparameshwaran rathinavel
2022-01-19  4:51         ` Stephen Hemminger
  -- strict thread matches above, loose matches on Subject: below --
2022-01-21  4:29 Kumara Parameshwaran
2022-01-24  9:47 ` Ferruh Yigit
2022-01-20 13:38 Kumara Parameshwaran
2022-01-20 13:26 Kumara Parameshwaran
2022-01-20 11:12 Kumara Parameshwaran
2022-01-20 15:49 ` Stephen Hemminger
2022-01-24  9:32 ` Ferruh Yigit
2021-11-25 12:25 Kumara Parameshwaran
2021-11-25 12:23 Kumara Parameshwaran
2021-11-25 12:04 Kumara Parameshwaran

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