Regarding port numbers assigned by DPDK for PCI devices

[Prashant Upadhyaya]

On Wed, 31 Jul 2024 at 14:35, Ferruh Yigit <ferruh.yigit at amd.com> wrote:

> On 7/30/2024 6:36 AM, Prashant Upadhyaya wrote:
> >
> >
> >
> > On Mon, 29 Jul 2024 at 23:13, Dmitry Kozlyuk <dmitry.kozliuk at gmail.com
> > <mailto:dmitry.kozliuk at gmail.com>> wrote:
> >
> >     2024-07-29 22:18 (UTC+0530), Prashant Upadhyaya:
> >     > Hi,
> >     >
> >     > I have 4 ethernet interfaces available as PCI devices.
> >     > The PCI addresses are known.
> >     > When I start my DPDK application, it starts up properly and
> >     assigns the
> >     > port numbers to them as 0, 1, 2, 3 expectedly.
> >     >
> >     > However, is there a way I can force that a particular PCI address
> >     should be
> >     > identified as port 0 by DPDK, another one as port 1 and so forth ?
> >     > Does passing the arguments like -a <address1> -a <address2> to
> >     rte_eal_init
> >     > ensure that, or is there any other way, or is there no way ?
> >     >
> >     > I am on 24.03
> >     >
> >     > Regards
> >     > -Prashant
> >
> >     Hi,
> >
> >     Why do you need specific port numbers assigned to devices?
> >
> >     If you're going to use devices for different purposes,
> >     you'd better have an application-level configuration
> >     to specify PCI addresses to use for each purpose.
> >     Iterate devices to match the address and find the port number.
> >
> >     It is also possible to disable automatic probing with "-a 0:0.0",
> >     then to use rte_dev_probe() + rte_dev_event_callback_register()
> >     to add devices and to get their port numbers.
> >     However, this API, strictly speaking, does not guarantee
> >     that the numbers will be assigned sequentially.
> >     One advantage of using hot-plug is that you can build devargs
> >     from within the application (or from configuration).
> >
> >     Refer to "rte_dev.h" in any case.
> >     Multiple "-a" don't work the way you've described.
> >
> >
> >
> > Thanks Dmitry. Ok, so if I have the port number with me, and I know it
> > corresponds to a PCI device, how do I find out the PCI address of this
> > device corresponding to this port number. I believe I can
> > do rte_eth_dev_info_get to get the struct rte_eth_dev_info and from
> > there the rte_device, but what after that ? I saw some references
> > to RTE_DEV_TO_PCI but that macro isn't available for compilation after
> > DPDK is installed as it is an internal header file and thus not a macro
> > for application usage and wouldn't compile at application level.
> >
> >
>
> Hi Prashant,
>
> For PCI bus, most of the times ethdev device name is PCI ID, so you can
> use 'rte_eth_dev_get_name_by_port(port_id, name)' API to get PCI ID for
> port.
>
> But there are cases this is not true, like single PCI ID creates
> multiple ethdev etc... for this case, PCI ID can be get from device name:
> rte_eth_dev_info_get(port_id, *dev_info)
> name = rte_dev_name(dev_info->device)
>
>
>
Thanks Ferruh, this was helpful.

Regards
-Prashant
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