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

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Date: Fri, 26 May 2023 17:01:49 +0800
From: Jiawen Wu <jiawenwu@...stnetic.com>
To: "'Russell King \(Oracle\)'" <linux@...linux.org.uk>
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 Friday, May 26, 2023 4:43 PM, Russell King (Oracle) wrote:
> 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.

Get it.