linux-kernel - Re: racing ndo_open()/phylink*connect() with phy

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Date: Wed, 1 May 2024 17:23:14 +0200
From: Andrew Lunn <andrew@...n.ch>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Andrew Halaney <ahalaney@...hat.com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-stm32@...md-mailman.stormreply.com, netdev@...r.kernel.org,
	alexandre.torgue@...s.st.com, joabreu@...opsys.com,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, mcoquelin.stm32@...il.com, hkallweit1@...il.com
Subject: Re: racing ndo_open()/phylink*connect() with phy_probe()

> > It seems unlikely, but one possibility is:
> > 
> > static int stmmac_xgmac2_mdio_read_c22(struct mii_bus *bus, int phyaddr,
> >                                        int phyreg)
> > {
> >         struct net_device *ndev = bus->priv;
> >         struct stmmac_priv *priv;
> >         u32 addr;
> > 
> >         priv = netdev_priv(ndev);
> > 
> >         /* Until ver 2.20 XGMAC does not support C22 addr >= 4 */
> >         if (priv->synopsys_id < DWXGMAC_CORE_2_20 &&
> >             phyaddr > MII_XGMAC_MAX_C22ADDR)
> >                 return -ENODEV;
> > 
> > Maybe if the interface is down, priv->synopsys_id has not been set
> > yet? Your devices are at address 8 and 10, so if priv->synopsys_id
> > where 0, this would give you the ENODEV.
> 
> Yes, I did look at that, but didn't read the DT snippet to realise
> that the addresses would be trapped by that. So, looking at where
> priv->synopsys_id is set... is in stmmac_hwif_init(), which is
> called from stmmac_hw_init(), which in turn is called from
> stmmac_dvr_probe(). This is the only path that leads here.
> 
> This all happens before the MDIO bus is registered, so the value of
> priv->synopsys_id should be set by the time the MDIO bus is registered.
> 
> So I'm unconvinced...

Me too. I just wanted to give an example of why it is important to
track down the source of the ENODEV.

      Andrew