[PATCH net-next v13 05/13] net: ethtool: Allow passing a phy index for some commands

[Andrew Lunn]

On Sun, Jun 16, 2024 at 06:02:31PM +0200, Maxime Chevallier wrote:
> Hello Jakub,
> 
> On Thu, 13 Jun 2024 18:26:13 -0700
> Jakub Kicinski <kuba at kernel.org> wrote:
> 
> > On Fri,  7 Jun 2024 09:18:18 +0200 Maxime Chevallier wrote:
> > > +		if (tb[ETHTOOL_A_HEADER_PHY_INDEX]) {
> > > +			struct nlattr *phy_id;
> > > +
> > > +			phy_id = tb[ETHTOOL_A_HEADER_PHY_INDEX];
> > > +			phydev = phy_link_topo_get_phy(dev,
> > > +						       nla_get_u32(phy_id));  
> > 
> > Sorry for potentially repeating question (please put the answer in the
> > commit message) - are phys guaranteed not to disappear, even if the
> > netdev gets closed? this has no rtnl protection
> 
> I'll answer here so that people can correct me if I'm wrong, but I'll
> also add it in the commit logs as well (and possibly with some fixes
> depending on how this discussion goes)
> 
> While a PHY can be attached to/detached from a netdevice at open/close,
> the phy_device itself will keep on living, as its lifetime is tied to
> the underlying mdio_device (however phy_attach/detach take a ref on the
> phy_device, preventing it from vanishing while it's attached to a
> netdev)

It gets interesting with copper SFP. They contain a PHY, and that PHY
can physically disappear at any time. What i don't know is when the
logical representation of the PHY will disappear after the hotunplug
event.

	Andrew