linux-kernel - Re: [PATCH net-next 3/3] net: phy: bcm54140: add hwmon support

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Message-ID: <20200419171231.GY25745@shell.armlinux.org.uk>
Date:   Sun, 19 Apr 2020 18:12:31 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Michael Walle <michael@...le.cc>, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH net-next 3/3] net: phy: bcm54140: add hwmon support

On Sun, Apr 19, 2020 at 06:29:28PM +0200, Andrew Lunn wrote:
> On Sun, Apr 19, 2020 at 12:29:23PM +0200, Michael Walle wrote:
> > Am 2020-04-17 23:28, schrieb Andrew Lunn:
> > > On Fri, Apr 17, 2020 at 11:08:56PM +0200, Michael Walle wrote:
> > > > Am 2020-04-17 22:13, schrieb Andrew Lunn:
> > > > > > Correct, and this function was actually stolen from there ;) This was
> > > > > > actually stolen from the mscc PHY ;)
> > > > >
> > > > > Which in itself indicates it is time to make it a helper :-)
> > > > 
> > > > Sure, do you have any suggestions?
> > > 
> > > mdiobus_get_phy() does the bit i was complaining about, the mdiobus
> > > internal knowledge.
> > 
> > But that doesn't address your other comment.
> 
> Yes, you are right. But i don't think you can easily generalize the
> rest. It needs knowledge of the driver private structure to reference
> pkg_init. You would have to move that into phy_device.
> 
> > 
> > > There is also the question of locking. What happens if the PHY devices
> > > is unbound while you have an instance of its phydev?
> > 
> > Is there any lock one could take to avoid that?
> 
> phy_attach_direct() does a get_device(). That at least means the
> struct device will not go away. I don't know the code well enough to
> know if that will also stop the phy_device structure from being freed.

Well, struct device is embedded in struct mdio_device, which in turn
is embedded in struct phy_device. So, if struct device can't go away
because its refcount is held, the same is true of the structs
embedding it.

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