netdev - Re: [PATCH net-next v7] ethtool: add netlink based get rss support

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Message-ID: <20221206161441.ziprba72sfydmjrk@lion.mk-sys.cz>
Date:   Tue, 6 Dec 2022 17:14:41 +0100
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Sudheer Mogilappagari <sudheer.mogilappagari@...el.com>,
        netdev@...r.kernel.org, andrew@...n.ch, corbet@....net,
        sridhar.samudrala@...el.com, anthony.l.nguyen@...el.com
Subject: Re: [PATCH net-next v7] ethtool: add netlink based get rss support

On Mon, Dec 05, 2022 at 09:45:07AM +0200, Leon Romanovsky wrote:
> On Sun, Dec 04, 2022 at 03:38:50PM -0800, Jakub Kicinski wrote:
> > Conversion to netlink stands on its own.
> 
> It doesn't answer on my question. The answer is "we do, just because
> we can" is nice but doesn't remove my worries that such "future"
> extension will work with real future feature. From my experience, many
> UAPI designs without real use case in hand will require adaptions and
> won't work out-of-box.
> 
> IMHO, it is the same sin as premature optimization.

Extensibility is likely the most obvious benefit of the netlink
interface but it's not the only one, even without an immediate need to
add a new feature, there are other benefits, e.g.

  - avoiding the inherently racy get/modify/set cycle
  - more detailed error reporting thanks to extack
  - notifications (ethtool --monitor)

And I'm pretty sure the list is not complete. Thus I believe converting
the ioctl UAPI to netlink is useful even without waiting until we need
to add new features that would require it.

Michal