netdev - RE: [PATCH net-next 1/2] nfp: initialize netdev's dev

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Date:   Thu, 30 Mar 2023 01:32:27 +0000
From:   Yinjun Zhang <yinjun.zhang@...igine.com>
To:     Leon Romanovsky <leon@...nel.org>,
        Louis Peens <louis.peens@...igine.com>
CC:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Simon Horman <simon.horman@...igine.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        oss-drivers <oss-drivers@...igine.com>
Subject: RE: [PATCH net-next 1/2] nfp: initialize netdev's dev_port with
 correct id

On Wed, 29 Mar 2023 21:49:59 +0300, Leon Romanovsky wrote:
> On Wed, Mar 29, 2023 at 04:45:47PM +0200, Louis Peens wrote:
> > From: Yinjun Zhang <yinjun.zhang@...igine.com>
> >
> > `dev_port` is used to differentiate devices that share the same
> > function, which is the case in most of NFP NICs.
> 
> And how did it work without dev_port?

No functionality fault, just cannot rename netdev as expected when the
udev rules use `dev_port` attribute as the example below.

> I have no idea what does it mean "different devices that share the same
> function".

That's how it's commented for the `dev_port` field of struct netdev:
*      @dev_port:              Used to differentiate devices that share
*                              the same function
I think it's used when single pci function instantiates more than one netdev.
Ref: 3f85944fe207 ("net: Add sysfs file for port number")

> 
> Thanks
> 
> >
> > In some customized scenario, `dev_port` is used to rename netdev
> > instead of `phys_port_name`, which requires to initialize it
> > correctly to get expected netdev name.
> >
> > Example rules using `dev_port`:
> >
> >   SUBSYSTEM=="net", ACTION=="add", KERNELS=="0000:e1:00.0",
> ATTR{dev_port}=="0", NAME:="ens8np0"
> >   SUBSYSTEM=="net", ACTION=="add", KERNELS=="0000:e1:00.0",
> ATTR{dev_port}=="1", NAME:="ens8np1"
> >