netdev - Re: [PATCH V2 net-next 2/5] net: Introduce a new MII time stamping interface.

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Message-ID: <20181007212118.GE25883@lunn.ch>
Date:   Sun, 7 Oct 2018 23:21:18 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Richard Cochran <richardcochran@...il.com>
Cc:     netdev@...r.kernel.org, devicetree@...r.kernel.org,
        David Miller <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jacob Keller <jacob.e.keller@...el.com>,
        Mark Rutland <mark.rutland@....com>,
        Miroslav Lichvar <mlichvar@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH V2 net-next 2/5] net: Introduce a new MII time stamping
 interface.

On Sun, Oct 07, 2018 at 02:07:28PM -0700, Richard Cochran wrote:
> On Sun, Oct 07, 2018 at 01:59:06PM -0700, Richard Cochran wrote:
> > On Sun, Oct 07, 2018 at 09:54:00PM +0200, Andrew Lunn wrote:
> > > 1) phylink, not phdev. We have been pushing some MAC drivers towards
> > > phylink, especially those which support >1Gbp.
> > 
> > If a phylink device appears that wants time stamping, can't we add the
> > call to register_mii_timestamper()?
> 
> Actually, I see that 'struct phylink' has a 'struct phy_device *phydev',
> and so it can implement the 'struct mii_timestamper' interface directly.

Maybe. But you still don't have skb->dev->phydev. And phylink->phydev
is much more dynamic, since it can be hot-{un}plugged. You need to
handle it going away at any time.

However, your timestamper is unlikely to be hot-{un}pluggable. So
skb->dev->mii_timestamper seems a lot safer.

       Andrew