net: asix: fix modprobe "sysfs: cannot create duplicate filename"

"modprobe asix ; rmmod asix ; modprobe asix" fails with:
   sysfs: cannot create duplicate filename \
   	'/devices/virtual/mdio_bus/usb-003:004'

Issue was originally reported by Anton Lundin on 2022-06-22 (link below).

Chrome OS team hit the same issue in Feb, 2023 when trying to find
work arounds for other issues with AX88172 devices.

The use of devm_mdiobus_register() with usbnet devices results in the
MDIO data being associated with the USB device. When the asix driver
is unloaded, the USB device continues to exist and the corresponding
"mdiobus_unregister()" is NOT called until the USB device is unplugged
or unauthorized. So the next "modprobe asix" will fail because the MDIO
phy sysfs attributes still exist.

The 'easy' (from a design PoV) fix is to use the non-devm variants of
mdiobus_* functions and explicitly manage this use in the asix_bind
and asix_unbind function calls. I've not explored trying to fix usbnet
initialization so devm_* stuff will work.

Fixes: e532a096be0e5 ("net: usb: asix: ax88772: add phylib support")
Reported-by: Anton Lundin <glance@acc.umu.se>
Link: https://lore.kernel.org/netdev/20220623063649.GD23685@pengutronix.de/T/
Tested-by: Eizan Miyamoto <eizan@chromium.org>
Signed-off-by: Grant Grundler <grundler@chromium.org>
Link: https://lore.kernel.org/r/20230321170539.732147-1-grundler@chromium.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/usb/asix_devices.c b/drivers/net/usb/asix_devices.c
index 743cbf5..f7cff58 100644 (file)
--- a/drivers/net/usb/asix_devices.c
+++ b/drivers/net/usb/asix_devices.c
@@ -666,8 +666,9 @@ static int asix_resume(struct usb_interface *intf)
 static int ax88772_init_mdio(struct usbnet *dev)
 {
        struct asix_common_private *priv = dev->driver_priv;
+       int ret;
 
-       priv->mdio = devm_mdiobus_alloc(&dev->udev->dev);
+       priv->mdio = mdiobus_alloc();
        if (!priv->mdio)
                return -ENOMEM;
 
@@ -679,7 +680,20 @@ static int ax88772_init_mdio(struct usbnet *dev)
        snprintf(priv->mdio->id, MII_BUS_ID_SIZE, "usb-%03d:%03d",
                 dev->udev->bus->busnum, dev->udev->devnum);
 
-       return devm_mdiobus_register(&dev->udev->dev, priv->mdio);
+       ret = mdiobus_register(priv->mdio);
+       if (ret) {
+               netdev_err(dev->net, "Could not register MDIO bus (err %d)\n", ret);
+               mdiobus_free(priv->mdio);
+               priv->mdio = NULL;
+       }
+
+       return ret;
+}
+
+static void ax88772_mdio_unregister(struct asix_common_private *priv)
+{
+       mdiobus_unregister(priv->mdio);
+       mdiobus_free(priv->mdio);
 }
 
 static int ax88772_init_phy(struct usbnet *dev)
@@ -896,16 +910,23 @@ static int ax88772_bind(struct usbnet *dev, struct usb_interface *intf)
 
        ret = ax88772_init_mdio(dev);
        if (ret)
-               return ret;
+               goto mdio_err;
 
        ret = ax88772_phylink_setup(dev);
        if (ret)
-               return ret;
+               goto phylink_err;
 
        ret = ax88772_init_phy(dev);
        if (ret)
-               phylink_destroy(priv->phylink);
+               goto initphy_err;
 
+       return 0;
+
+initphy_err:
+       phylink_destroy(priv->phylink);
+phylink_err:
+       ax88772_mdio_unregister(priv);
+mdio_err:
        return ret;
 }
 
@@ -926,6 +947,7 @@ static void ax88772_unbind(struct usbnet *dev, struct usb_interface *intf)
        phylink_disconnect_phy(priv->phylink);
        rtnl_unlock();
        phylink_destroy(priv->phylink);
+       ax88772_mdio_unregister(priv);
        asix_rx_fixup_common_free(dev->driver_priv);
 }