[PATCH net 2/4] net: phy: propagate MII register write errors

[James Hilliard <james.hilliard1@gmail.com>]

phy_mii_ioctl() ignores MDIO write failures and can report success after a
failed write. It also updates the cached link settings and may restart
auto-negotiation or reinitialize the PHY even though the requested write
failed.

Check the write result before updating the cached settings or invoking
those follow-up operations, and return the MDIO error to the caller.

Fixes: 00db8189d984 ("This patch adds a PHY Abstraction Layer to the Linux Kernel, enabling ethernet drivers to remain as ignorant as is reasonable of the connected PHY's design and operation details.")
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
 drivers/net/phy/phy.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index fce9bc7be330..4ac72a1b4f42 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -350,6 +350,15 @@ int phy_mii_ioctl(struct phy_device *phydev, struct ifreq *ifr, int cmd)
 			prtad = mii_data->phy_id;
 			devad = mii_data->reg_num;
 		}
+
+		if (mdio_phy_id_is_c45(mii_data->phy_id))
+			ret = mdiobus_c45_write(phydev->mdio.bus, prtad, devad,
+						mii_data->reg_num, val);
+		else
+			ret = mdiobus_write(phydev->mdio.bus, prtad, devad, val);
+		if (ret < 0)
+			return ret;
+
 		if (prtad == phydev->mdio.addr) {
 			switch (devad) {
 			case MII_BMCR:
@@ -388,12 +397,6 @@ int phy_mii_ioctl(struct phy_device *phydev, struct ifreq *ifr, int cmd)
 			}
 		}
 
-		if (mdio_phy_id_is_c45(mii_data->phy_id))
-			mdiobus_c45_write(phydev->mdio.bus, prtad, devad,
-					  mii_data->reg_num, val);
-		else
-			mdiobus_write(phydev->mdio.bus, prtad, devad, val);
-
 		if (prtad == phydev->mdio.addr &&
 		    devad == MII_BMCR &&
 		    val & BMCR_RESET)

-- 
2.53.0