Re: [PATCH net-next RFC V1 3/5] net: Introduce field for the MII time stamper.

Richard Cochran
2018-03-21T21:51:54Z

On Wed, Mar 21, 2018 at 12:12:00PM -0700, Florian Fainelli wrote:
> > +static int mdiobus_netdev_notification(struct notifier_block *nb,
> > + unsigned long msg, void *ptr)
> > +{
> > + struct net_device *netdev = netdev_notifier_info_to_dev(ptr);
> > + struct phy_device *phydev = netdev->phydev;
> > + struct mdio_device *mdev;
> > + struct mii_bus *bus;
> > + int i;
> > +
> > + if (netdev->mdiots || msg != NETDEV_UP || !phydev)
> > + return NOTIFY_DONE;
>
> You are still assuming that we have a phy_device somehow, whereas you
> parch series wants to solve that for generic MDIO devices, that is a bit
> confusing.

The phydev is the only thing that associates a netdev with an MII bus.

> > +
> > + /*
> > + * Examine the MII bus associated with the PHY that is
> > + * attached to the MAC. If there is a time stamping device
> > + * on the bus, then connect it to the network device.
> > + */
> > + bus = phydev->mdio.bus;
> > +
> > + for (i = 0; i < PHY_MAX_ADDR; i++) {
> > + mdev = bus->mdio_map[i];
> > + if (!mdev)
> > + continue;
> > + if (mdiodev_supports_timestamping(mdev)) {
> > + netdev->mdiots = mdev;
> > + return NOTIFY_OK;
>
> What guarantees that netdev->mdiots gets cleared?

Why would it need to be cleared?

> Also, why is this done
> with a notifier instead of through phy_{connect,attach,disconnect}?

We have no guarantee the mdio device has been probed yet.

> It
> looks like we still have this requirement of the mdio TS device being a
> phy_device somehow, I am confused here...

We only need the phydev to get from the netdev to the mii bus.

> > + }
> > + }
> > +
> > + return NOTIFY_DONE;
> > +}
> > +
> > #ifdef CONFIG_PM
> > static int mdio_bus_suspend(struct device *dev)
> > {
>
> > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > index 5fbb9f1da7fd..223d691aa0b0 100644
> > --- a/include/linux/netdevice.h
> > +++ b/include/linux/netdevice.h
> > @@ -1943,6 +1943,7 @@ struct net_device {
> > struct netprio_map __rcu *priomap;
> > #endif
> > struct phy_device *phydev;
> > + struct mdio_device *mdiots;
>
> phy_device embedds a mdio_device, can you find a way to rework the PHY
> PTP code to utilize the phy_device's mdio instance so do not introduce
> yet another pointer in that big structure that net_device already is?

It would be strange and wrong to "steal" the phy's mdio struct, IMHO.
After all, we just got support for non-PHY mdio devices. The natural
solution is to use it.

Thanks,
Richard