netdev - Re: [PATCH net] net: phy: Fix lack of reference count on PHY driver

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Message-ID: <20170201191024.GQ27312@n2100.armlinux.org.uk>
Date:   Wed, 1 Feb 2017 19:10:24 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     David Miller <davem@...emloft.net>
Cc:     f.fainelli@...il.com, netdev@...r.kernel.org, andrew@...n.ch,
        maowenan@...wei.com
Subject: Re: [PATCH net] net: phy: Fix lack of reference count on PHY driver

On Wed, Feb 01, 2017 at 01:59:38PM -0500, David Miller wrote:
> From: Florian Fainelli <f.fainelli@...il.com>
> Date: Wed, 1 Feb 2017 10:55:46 -0800
> 
> > You are right, but there is still a fundamental problem IMHO in that you
> > should not be able to rmmod a PHY driver as long as a network device is
> > attached to the PHY, and if the PHY driver is attached from several
> > different network devices, they should all have a way to prevent a PHY
> > driver rmmod, each of them incrementing the driver refcount, which is
> > what the patche from Maowan does here.
> 
> It briefly occurred to me that we might want to be able to disconnect
> PHYs to allow an unload using notifiers, the same way that when you
> take a netdevice down we emit notifiers so that all of the references
> to the netdevice can release themselves.
> 
> I have no idea how well that would work, or whether it is valuable or
> not.  But it is another way to handle this.
> 
> But that is a longer-term thing even if we want to go that way, and
> thus grabbing the proper refs is the right things to do for now.

It's something I'm effectively already doing as part of my phylink
project for SFP support, since you can hot-unplug a copper SFP
module, and the PHY on the copper SFP module will be gone.  phylink,
however, sits between the network driver and phylib, which isn't
ideal.

-- 
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