netdev - Re: [RFC 3/4] wwan: add interface creation support

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Message-ID: <CAHNKnsRv3r=Y7fTR-kUNVXyqeKiugXwAmzryBPvwYpxgjgBeBA@mail.gmail.com>
Date:   Wed, 2 Jun 2021 04:42:41 +0300
From:   Sergey Ryazanov <ryazanov.s.a@...il.com>
To:     Johannes Berg <johannes@...solutions.net>,
        Loic Poulain <loic.poulain@...aro.org>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        m.chetan.kumar@...el.com, Johannes Berg <johannes.berg@...el.com>
Subject: Re: [RFC 3/4] wwan: add interface creation support

Hello Johannes and Loic,

On Tue, Jun 1, 2021 at 11:07 AM Johannes Berg <johannes@...solutions.net> wrote:
> Add support to create (and destroy) interfaces via a new
> rtnetlink kind "wwan". The responsible driver has to use
> the new wwan_register_ops() to make this possible.

Wow, this is a perfect solution! I just could not help but praise this
proposal :)

When researching the latest WWAN device drivers and related
discussions, I began to assume that implementing the netdev management
API without the dummy (no-op) netdev is only possible using genetlink.
But this usage of a regular device specified by its name as a parent
for netdev creation is so natural and clear that I believe in RTNL
again.

Let me place my 2 cents. Maybe the parent device attribute should be
made generic? E.g. call it IFLA_PARENT_DEV_NAME, with usage semantics
similar to the IFLA_LINK attribute for VLAN interfaces. The case when
a user needs to create a netdev on behalf of a regular device is not
WWAN specific, IMHO. So, other drivers could benefit from such
attribute too. To be honest, I can not recall any driver that could
immediately start using such attribute, but the situation with the
need for such attribute seems to be quite common.

-- 
Sergey