Re: [PATCH net] net: phy: allow phy_detach() before netdev registration

[Chenguang Zhao <chenguang.zhao@linux.dev>]

On Mon, Sep 21, 2026 at 02:15:58PM +0200, Andrew Lunn wrote:
> > > Lets zoom out and look at the big picture....
> > > 
> > > Why is phy_detach() not symmetric with phy_attach()?
> > > 
> > > Why is phy_detach() touching dev->hwprov, when phy_attach() does not?
> > > 
> > > Where is dev->hwprov set and why is the mirror function not dealing
> > > with this?
> 
> > The dev->hwprov is set by ETHTOOL_MSG_TSCONFIG_SET in
> > ethnl_set_tsconfig(), which is the only writer besides phy_detach().
> 
> So this is the real problem. It does not fit the usual pattern of
> setup and tairdown.
> 
> > phy_detach() clears hwprov only when the selected provider is this PHY,
> > so skb_clone_tx_timestamp() / skb_defer_rx_timestamp() do not keep a
> > dangling phydev pointer after the PHY is gone. That is not the reverse
> > of phy_attach(); it is lifetime cleanup for a pointer that ethtool
> > stashed in the netdev.
> 
> Can we make it fit the usual pattern?
> 
> https://elixir.bootlin.com/linux/v7.2.5/source/net/ethtool/tsconfig.c#L413
> 
> This sets the stamper to zero_config, via dev_set_hwtstamp_phylib().
> Could that be done in phy_attach()?  phy_detach() would then have the
> opposite, call dev_clear_hwtstamp_phylib().
> 
> ethnl_set_tsconfig() then just replaces the setting?
> 
> I would put dev_clear_hwtstamp_phylib() next to
> dev_set_hwtstamp_phylib() so it is obvious the locking is the same in
> both.
> 
> 	Andrew

Hi Andrew,

I've just sent out v3, addressing your comments on the provider lifetime
asymmetry.

https://lore.kernel.org/all/20260923071132.908826-1-chenguang.zhao@linux.dev/

Happy to iterate further if anything still needs adjustment.

Thanks,
Chenguang