netdev - Re: [PATCH net-next] net: phylink: propagate phy_attach

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Date:   Sun, 15 Dec 2019 07:43:15 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Milind Parab <mparab@...ence.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: phylink: propagate phy_attach_direct()
 return code

On Sat, Dec 14, 2019 at 08:27:45PM -0800, Jakub Kicinski wrote:
> On Thu, 12 Dec 2019 17:16:12 +0000, Russell King wrote:
> > of_phy_attach() hides the return value of phy_attach_direct(), forcing
> > us to return a "generic" ENODEV error code that is indistinguishable
> > from the lack-of-phy-property case.
> > 
> > Switch to using of_phy_find_device() to find the PHY device, and then
> > propagating any phy_attach_direct() error back to the caller.
> > 
> > Link: https://lore.kernel.org/lkml/20191210113829.GT25745@shell.armlinux.org.uk
> > Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
> 
> Applied thanks, the ref counting is not entirely obvious to a layman.
> In your reply to Milind you said he can immediately of_node_put()
> because the phy_dev is never deferenced in his code, but here it looks
> like it is actually - the reference used to be given up after attach is
> done, now its given up before attach_direct is called.

The refcount is on the device_node - once we've got the phy device
itself (or failed to) we're not using the device_node anymore, so
we can put it directly after the of_phy_find_device() call.

> 
> But I don't know how the refcounting here works, so applied, and on the
> off chance the code is wrong follow up will be fine.
> 
> > diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> > index f7c660bf99d1..8d20cf3ba0b7 100644
> > --- a/drivers/net/phy/phylink.c
> > +++ b/drivers/net/phy/phylink.c
> > @@ -859,14 +859,17 @@ int phylink_of_phy_connect(struct phylink *pl, struct device_node *dn,
> >  		return 0;
> >  	}
> >  
> > -	phy_dev = of_phy_attach(pl->netdev, phy_node, flags,
> > -				pl->link_interface);
> > +	phy_dev = of_phy_find_device(phy_node);
> >  	/* We're done with the phy_node handle */
> >  	of_node_put(phy_node);
> > -
> >  	if (!phy_dev)
> >  		return -ENODEV;
> >  
> > +	ret = phy_attach_direct(pl->netdev, phy_dev, flags,
> > +				pl->link_interface);
> > +	if (ret)
> > +		return ret;
> > +
> >  	ret = phylink_bringup_phy(pl, phy_dev, pl->link_config.interface);
> >  	if (ret)
> >  		phy_detach(phy_dev);
> 
> 

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