netdev - Re: [PATCH ethtool] ethtool: add support show/set-hwtstamp

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Date:   Wed, 2 Sep 2020 14:06:54 -0400
From:   Kevin Yang <yyd@...gle.com>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     Andrew Lunn <andrew@...n.ch>, Networking <netdev@...r.kernel.org>,
        Neal Cardwell <ncardwell@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH ethtool] ethtool: add support show/set-hwtstamp

On Wed, Sep 2, 2020 at 3:04 AM Michal Kubecek <mkubecek@...e.cz> wrote:
>
> On Tue, Sep 01, 2020 at 08:36:08PM -0400, Kevin Yang wrote:
> > On Tue, Sep 1, 2020 at 6:02 PM Andrew Lunn <andrew@...n.ch> wrote:
> > > On Tue, Sep 01, 2020 at 05:20:09PM -0400, Kevin(Yudong) Yang wrote:
> > > > Before this patch, ethtool has -T/--show-time-stamping that only
> > > > shows the device's time stamping capabilities but not the time
> > > > stamping policy that is used by the device.
> > >
> > > How does this differ from hwstamp_ctl(1)?
> >
> > They are pretty much the same, both use ioctl(SIOCSHWTSTAMP).
> >
> > Adding this to ethtool is because:
> > - This time stamping policy is a hardware setting aligned with ethtool's
> > purpose "query and control network device driver and hardware settings"
> > - ethtool is widely used, system administrators don't need to install
> > another binary to control this feature.
>
> Adding this feature to ethtool IMHO makes good sense, I'm just not sure
> if it's necessary to add new subcommands, perhaps we could add the
> "show" part to -T / --show-time-stamping and add --set-time-stamping.

Thanks for the nice suggestion. This sounds good to me, I will work on v2
to have:
"-T / --show-time-stamping" to show capabilities AND current policy;
and "--set-time-stamping" to change the policy.

> However, I don't like the idea of adding a new ioctl based interface to
> ethtool while we are working on replacing and deprecating existing one.
> I would much rather like adding this to the netlink interface (which
> would, of course, require also kernel side implementation).
>
> Michal