Re: [PATCH RFC net-next] net: phy: add Marvell PHY PTP support

[Russell King - ARM Linux admin <linux@armlinux.org.uk>]

On Thu, Jul 30, 2020 at 12:32:45PM -0700, Richard Cochran wrote:
> On Thu, Jul 30, 2020 at 07:38:00PM +0100, Russell King - ARM Linux admin wrote:
> > What I ended up doing was:
> > 
> >         if (ops->get_ts_info) {
> >                 ret = ops->get_ts_info(dev, info);
> >                 if (ret != -EOPNOTSUPP)
> >                         return ret;
> >         }
> >         if (phy_has_tsinfo(phydev))
> >                 return phy_ts_info(phydev, info);
> > ...
> > 
> > which gives the MAC first refusal.  If the MAC wishes to defer to
> > phylib or the default, it can just return -EOPNOTSUPP.
> 
> I guess that makes sense.  If someone designs a board that happens to
> have a PHY with unwanted time stamping fcunctionality, then at least
> the MAC time stamping function will work.  If the designers really
> want PHY time stamping, then they are likely to have to patch the MAC
> driver in any case.
> 
> So I'm not against such a change.  It would be important to keep the
> current "PHY-friendly" MAC drivers still friendly, and so they would
> need patching as part of the change.

That would only be necessary if they also provide the get_ts_info
method.

So, I guess I need to find all drivers that refer to phylink or phylib
functions, that also implement get_ts_info method and review them.
I would expect that to be very small, since there's currently little
point implementing PTP at both the PHY and the MAC for the reason I've
raised earlier in this thread.

-- 
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