net: ethernet: fix suspend/resume in davinci_emac

This patch reverts commit 3243ff2a05ec ("net: ethernet: davinci_emac:
Deduplicate bus_find_device() by name matching") and adds a comment
which should stop anyone from reintroducing the same "fix" in the future.

We can't use bus_find_device_by_name() here because the device name is
not guaranteed to be 'davinci_mdio'. On some systems it can be
'davinci_mdio.0' so we need to use strncmp() against the first part of
the string to correctly match it.

Fixes: 3243ff2a05ec ("net: ethernet: davinci_emac: Deduplicate bus_find_device() by name matching")
Cc: stable@vger.kernel.org
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/ti/davinci_emac.c b/drivers/net/ethernet/ti/davinci_emac.c
index 06d7c9e4dcda92deb027522dc04b34326c9fdc8a..a1a6445b5a7e2568af9e876f346b124958a51eee 100644 (file)
--- a/drivers/net/ethernet/ti/davinci_emac.c
+++ b/drivers/net/ethernet/ti/davinci_emac.c
@@ -1385,6 +1385,11 @@ static int emac_devioctl(struct net_device *ndev, struct ifreq *ifrq, int cmd)
                return -EOPNOTSUPP;
 }
 
+static int match_first_device(struct device *dev, void *data)
+{
+       return !strncmp(dev_name(dev), "davinci_mdio", 12);
+}
+
 /**
  * emac_dev_open - EMAC device open
  * @ndev: The DaVinci EMAC network adapter
@@ -1484,8 +1489,14 @@ static int emac_dev_open(struct net_device *ndev)
 
        /* use the first phy on the bus if pdata did not give us a phy id */
        if (!phydev && !priv->phy_id) {
-               phy = bus_find_device_by_name(&mdio_bus_type, NULL,
-                                             "davinci_mdio");
+               /* NOTE: we can't use bus_find_device_by_name() here because
+                * the device name is not guaranteed to be 'davinci_mdio'. On
+                * some systems it can be 'davinci_mdio.0' so we need to use
+                * strncmp() against the first part of the string to correctly
+                * match it.
+                */
+               phy = bus_find_device(&mdio_bus_type, NULL, NULL,
+                                     match_first_device);
                if (phy) {
                        priv->phy_id = dev_name(phy);
                        if (!priv->phy_id || !*priv->phy_id)