linux-kernel - Re: [PATCH net 1/2] of: of_mdio: Correct loop scanning logic

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Message-ID: <20200619132101.GA304147@lunn.ch>
Date:   Fri, 19 Jun 2020 15:21:01 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     netdev@...r.kernel.org, Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Dajun Jin <adajunjin@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH net 1/2] of: of_mdio: Correct loop scanning logic

On Thu, Jun 18, 2020 at 09:47:58PM -0700, Florian Fainelli wrote:
> Commit 209c65b61d94 ("drivers/of/of_mdio.c:fix of_mdiobus_register()")
> introduced a break of the loop on the premise that a successful
> registration should exit the loop. The premise is correct but not to
> code, because rc && rc != -ENODEV is just a special error condition,
> that means we would exit the loop even with rc == -ENODEV which is
> absolutely not correct since this is the error code to indicate to the
> MDIO bus layer that scanning should continue.
> 
> Fix this by explicitly checking for rc = 0 as the only valid condition
> to break out of the loop.
> 
> Fixes: 209c65b61d94 ("drivers/of/of_mdio.c:fix of_mdiobus_register()")
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  drivers/of/of_mdio.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
> index a04afe79529c..7496dc64d6b5 100644
> --- a/drivers/of/of_mdio.c
> +++ b/drivers/of/of_mdio.c
> @@ -315,9 +315,10 @@ int of_mdiobus_register(struct mii_bus *mdio, struct device_node *np)
>  
>  			if (of_mdiobus_child_is_phy(child)) {
>  				rc = of_mdiobus_register_phy(mdio, child, addr);
> -				if (rc && rc != -ENODEV)
> +				if (!rc)
> +					break;

Maybe add in a comment here about what ENODEV means in this context?
That might avoid it getting broken again in the future.

> +				if (rc != -ENODEV)
>  					goto unregister;
> -				break;
>  			}
>  		}
>  	}
> -- 

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew