netdev - Re: [PATCH net-next v9 8/9] net: txgbe: Implement phylink pcs

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Date: Fri, 26 May 2023 09:43:16 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Jiawen Wu <jiawenwu@...stnetic.com>
Cc: 'Jakub Kicinski' <kuba@...nel.org>, netdev@...r.kernel.org,
	jarkko.nikula@...ux.intel.com, andriy.shevchenko@...ux.intel.com,
	mika.westerberg@...ux.intel.com, jsd@...ihalf.com,
	Jose.Abreu@...opsys.com, andrew@...n.ch, hkallweit1@...il.com,
	linux-i2c@...r.kernel.org, linux-gpio@...r.kernel.org,
	mengyuanlou@...-swift.com
Subject: Re: [PATCH net-next v9 8/9] net: txgbe: Implement phylink pcs

On Fri, May 26, 2023 at 02:21:23PM +0800, Jiawen Wu wrote:
> On Friday, May 26, 2023 12:14 PM, Jakub Kicinski wrote:
> > On Wed, 24 May 2023 17:17:21 +0800 Jiawen Wu wrote:
> > > +	ret = devm_mdiobus_register(&pdev->dev, mii_bus);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	mdiodev = mdio_device_create(mii_bus, 0);
> > > +	if (IS_ERR(mdiodev))
> > > +		return PTR_ERR(mdiodev);
> > > +
> > > +	xpcs = xpcs_create(mdiodev, PHY_INTERFACE_MODE_10GBASER);
> > > +	if (IS_ERR(xpcs)) {
> > > +		mdio_device_free(mdiodev);
> > > +		return PTR_ERR(xpcs);
> > > +	}
> > 
> > How does the mdiodev get destroyed in case of success?
> > Seems like either freeing it in case of xpcs error is unnecessary
> > or it needs to also be freed when xpcs is destroyed?
> 
> When xpcs is destroyed, that means mdiodev is no longer needed.
> I think there is no need to free mdiodev in case of xpcs error,
> since devm_* function leads to free it.

If you are relying on the devm-ness of devm_mdiobus_register() then
it won't. Although mdiobus_unregister() walks bus->mdio_map[], I
think you are assuming that the mdio device you've created in
mdio_device_create() will be in that array. MDIO devices only get
added to that array when mdiobus_register_device() has been called,
which must only be called from mdio_device_register().

Please arrange to call mdio_device_free() prior to destroying the
XPCS in every case.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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