linux-kernel - [PATCH net v2 1/2] of: of_mdio: Correct loop scanning logic

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Date:   Fri, 19 Jun 2020 11:47:46 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     netdev@...r.kernel.org
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        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>,
        linux-kernel@...r.kernel.org (open list),
        devicetree@...r.kernel.org (open list:OPEN FIRMWARE AND FLATTENED
        DEVICE TREE)
Subject: [PATCH net v2 1/2] of: of_mdio: Correct loop scanning logic

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()")
Reviewed-by: Andrew Lunn <andrew@...n.ch>
Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
---
 drivers/of/of_mdio.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
index a04afe79529c..ef6f818ce5b3 100644
--- a/drivers/of/of_mdio.c
+++ b/drivers/of/of_mdio.c
@@ -314,10 +314,15 @@ int of_mdiobus_register(struct mii_bus *mdio, struct device_node *np)
 				 child, addr);
 
 			if (of_mdiobus_child_is_phy(child)) {
+				/* -ENODEV is the return code that PHYLIB has
+				 * standardized on to indicate that bus
+				 * scanning should continue.
+				 */
 				rc = of_mdiobus_register_phy(mdio, child, addr);
-				if (rc && rc != -ENODEV)
+				if (!rc)
+					break;
+				if (rc != -ENODEV)
 					goto unregister;
-				break;
 			}
 		}
 	}
-- 
2.17.1