netdev - Re: [PATCH 0/2] net: phy: relax error checking when creating sysfs link netdev->phydev

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Message-ID: <20180316172234.GA4212@lunn.ch>
Date:   Fri, 16 Mar 2018 18:22:34 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sekhar Nori <nsekhar@...com>, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org
Subject: Re: [PATCH 0/2] net: phy: relax error checking when creating sysfs
 link netdev->phydev

On Wed, Mar 14, 2018 at 05:26:22PM -0500, Grygorii Strashko wrote:
> Some ethernet drivers (like TI CPSW) may connect and manage >1 Net PHYs per
> one netdevice, as result such drivers will produce warning during system
> boot and fail to connect second phy to netdevice when PHYLIB framework
> will try to create sysfs link netdev->phydev for second PHY
> in phy_attach_direct(), because sysfs link with the same name has been
> created already for the first PHY.
> As result, second CPSW external port will became unusable.
> This issue was introduced by commits:
> 5568363f0cb3 ("net: phy: Create sysfs reciprocal links for attached_dev/phydev"
> a3995460491d ("net: phy: Relax error checking on sysfs_create_link()"

I wonder if it would be better to add a flag to the phydev that
indicates it is the second PHY connected to a MAC? Add a bit to
phydrv->mdiodrv.flags. If that bit is set, don't create the sysfs
file.

For 99% of MAC drivers, having two PHYs is an error, so we want to aid
debug by reporting the sysfs error.

      Andrew