Re: assert in phylink.c with lan7801 and dp83tc811 since kernel 6.18

[Andrew Lunn <andrew@lunn.ch>]

> [    2.339481] lan78xx 1-1.3:1.0 (unnamed net_device) (uninitialized): can't attach PHY to usb-001:003, error -EINVAL

static int lan78xx_phy_init(struct lan78xx_net *dev)
{
...

       ret = phylink_connect_phy(dev->phylink, phydev);
        if (ret) {
                netdev_err(dev->net, "can't attach PHY to %s, error %pe\n",
                           dev->mdiobus->id, ERR_PTR(ret));
                goto phylink_uninit;
        }

This is the error message we see.

phylink_uninit:
        lan78xx_phy_uninit(dev);

        return ret;
}

and

static void lan78xx_phy_uninit(struct lan78xx_net *dev)
{
        if (dev->phylink) {
                phylink_disconnect_phy(dev->phylink);
                phylink_destroy(dev->phylink);
                dev->phylink = NULL;
        }
}

We see the error message because phylink_connect_phy() failed. If
connect failed, you should not call disconnect.

The general pattern in Linux is that you undo what went correctly at
the end of the function.

Please try this patch.

       Andrew

From ea55645b23092a0de7aa3ab0eaf7bcb73a7fb0e1 Mon Sep 17 00:00:00 2001
From: Andrew Lunn <andrew@lunn.ch>
Date: Wed, 6 May 2026 08:10:29 -0500
Subject: [PATCH] net: usb: lan78xx: Fix cleanup in lan78xx_phy_init

If phylink_connect_phy() fails, phylink_disconnect() should not be
called. Rather than use lan78xx_phy_uninit() which does too much, add
the cleanup at the end of the function and only undo what was
successfully done.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
---
 drivers/net/usb/lan78xx.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index bcf293ea1bd3..9cfc122d76ef 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2842,7 +2842,7 @@ static int lan78xx_phy_init(struct lan78xx_net *dev)
 
 	ret = lan78xx_mac_prepare_for_phy(dev);
 	if (ret < 0)
-		goto phylink_uninit;
+		goto destroy_phylink;
 
 	/* If no PHY is found, set up a fixed link. It is very specific to
 	 * the LAN7801 and is used in special cases like EVB-KSZ9897-1 where
@@ -2852,7 +2852,7 @@ static int lan78xx_phy_init(struct lan78xx_net *dev)
 	if (!phydev) {
 		ret = lan78xx_set_fixed_link(dev);
 		if (ret < 0)
-			goto phylink_uninit;
+			goto destroy_phylink;
 
 		/* No PHY found, so set up a fixed link and return early.
 		 * No need to configure PHY IRQ or attach to phylink.
@@ -2871,17 +2871,19 @@ static int lan78xx_phy_init(struct lan78xx_net *dev)
 	if (ret) {
 		netdev_err(dev->net, "can't attach PHY to %s, error %pe\n",
 			   dev->mdiobus->id, ERR_PTR(ret));
-		goto phylink_uninit;
+		goto destroy_phylink;
 	}
 
 	ret = lan78xx_configure_leds_from_dt(dev, phydev);
 	if (ret < 0)
-		goto phylink_uninit;
+		goto disconnect_phylink;
 
 	return 0;
 
-phylink_uninit:
-	lan78xx_phy_uninit(dev);
+disconnect_phylink:
+	phylink_disconnect_phy(dev->phylink);
+destroy_phylink:
+	phylink_destroy(dev->phylink);
 
 	return ret;
 }
-- 
2.53.0