netdev - [Stlinux-devel] [PATCH linux-stm 1/4] net:stmmac: Add check if mdiobus is registered in stmmac_mdio

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Message-Id: <1346341798-19704-1-git-send-email-srinivas.kandagatla@st.com>
Date:	Thu, 30 Aug 2012 16:49:58 +0100
From:	Srinivas KANDAGATLA <srinivas.kandagatla@...com>
To:	netdev@...r.kernel.org
Cc:	peppe.cavallaro@...com
Subject: [Stlinux-devel] [PATCH linux-stm 1/4] net:stmmac: Add check if mdiobus is registered in stmmac_mdio_unregister

From: Srinivas Kandagatla <srinivas.kandagatla@...com>

This patch adds a basic check in stmmac_mdio_unregister to see if mdio
bus registeration for this driver was actually sucessfull or not.

Use case here is, if BSP considers using mdio-gpio bus along with stmmac
driver by passing mdio_bus_data as NULL in platform data.
Call to stmmac_mdio_register with mdio_bus_data as NULL returns 0, which
is a considered sucessfull call form stmmac. Then again when we unload
the driver we just call stmmac_mdio_unregister, this is were the actual
problem is stmmac-mdio code dont really know at this instance of calling
that stmmac_mdio_register was actually successful.

So Adding a check in stmmac_mdio_unregister is always safe.

Without this patch stmmac driver calls stmmac_mdio_register from
stmmac_release which Segfaults as mii bus was never registered at the
first point.

Originally the this bug was found when unloading an stmmac driver
instance which uses mdio-gpio for smi access.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
index ade1082..e1f3d04 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
@@ -258,6 +258,9 @@ int stmmac_mdio_unregister(struct net_device *ndev)
 {
 	struct stmmac_priv *priv = netdev_priv(ndev);

+	if (!priv->mii)
+		return 0;
+
 	mdiobus_unregister(priv->mii);
 	priv->mii->priv = NULL;
 	mdiobus_free(priv->mii);
-- 
1.7.0.4

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