[PATCH v2 net-next] net: stmmac: mdio: fix incorrect phy address check

[PATCH v2 net-next] net: stmmac: mdio: fix incorrect phy address check

[Heiner Kallweit]

max_addr is the max number of addresses, not the highest possible address,
therefore check phydev->mdio.addr > max_addr isn't correct.
To fix this change the semantics of max_addr, so that it represents
the highest possible address. IMO this is also a little bit more intuitive
wrt name max_addr.

Fixes: 4a107a0e8361 ("net: stmmac: mdio: use phy_find_first to simplify stmmac_mdio_register")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Reported-by: Simon Horman <horms@kernel.org>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
v2:
- improve subject
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
index 3f8cc3293..1e82850f2 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
@@ -583,9 +583,9 @@ int stmmac_mdio_register(struct net_device *ndev)
 	struct device_node *mdio_node = priv->plat->mdio_node;
 	struct device *dev = ndev->dev.parent;
 	struct fwnode_handle *fixed_node;
+	int max_addr = PHY_MAX_ADDR - 1;
 	struct fwnode_handle *fwnode;
 	struct phy_device *phydev;
-	int max_addr;
 
 	if (!mdio_bus_data)
 		return 0;
@@ -609,15 +609,12 @@ int stmmac_mdio_register(struct net_device *ndev)
 
 		if (priv->synopsys_id < DWXGMAC_CORE_2_20) {
 			/* Right now only C22 phys are supported */
-			max_addr = MII_XGMAC_MAX_C22ADDR + 1;
+			max_addr = MII_XGMAC_MAX_C22ADDR;
 
 			/* Check if DT specified an unsupported phy addr */
 			if (priv->plat->phy_addr > MII_XGMAC_MAX_C22ADDR)
 				dev_err(dev, "Unsupported phy_addr (max=%d)\n",
 					MII_XGMAC_MAX_C22ADDR);
-		} else {
-			/* XGMAC version 2.20 onwards support 32 phy addr */
-			max_addr = PHY_MAX_ADDR;
 		}
 	} else {
 		new_bus->read = &stmmac_mdio_read_c22;
@@ -626,8 +623,6 @@ int stmmac_mdio_register(struct net_device *ndev)
 			new_bus->read_c45 = &stmmac_mdio_read_c45;
 			new_bus->write_c45 = &stmmac_mdio_write_c45;
 		}
-
-		max_addr = PHY_MAX_ADDR;
 	}
 
 	if (mdio_bus_data->needs_reset)
-- 
2.51.1

Re: [PATCH v2 net-next] net: stmmac: mdio: fix incorrect phy address check

[Simon Horman]

On Sat, Oct 25, 2025 at 08:35:47PM +0200, Heiner Kallweit wrote:
> max_addr is the max number of addresses, not the highest possible address,
> therefore check phydev->mdio.addr > max_addr isn't correct.
> To fix this change the semantics of max_addr, so that it represents
> the highest possible address. IMO this is also a little bit more intuitive
> wrt name max_addr.
> 
> Fixes: 4a107a0e8361 ("net: stmmac: mdio: use phy_find_first to simplify stmmac_mdio_register")
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Reported-by: Simon Horman <horms@kernel.org>
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
> v2:
> - improve subject

Thanks, this versions looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>

...

Re: [PATCH v2 net-next] net: stmmac: mdio: fix incorrect phy address check

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Sat, 25 Oct 2025 20:35:47 +0200 you wrote:
> max_addr is the max number of addresses, not the highest possible address,
> therefore check phydev->mdio.addr > max_addr isn't correct.
> To fix this change the semantics of max_addr, so that it represents
> the highest possible address. IMO this is also a little bit more intuitive
> wrt name max_addr.
> 
> Fixes: 4a107a0e8361 ("net: stmmac: mdio: use phy_find_first to simplify stmmac_mdio_register")
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Reported-by: Simon Horman <horms@kernel.org>
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> 
> [...]

Here is the summary with links:
  - [v2,net-next] net: stmmac: mdio: fix incorrect phy address check
    https://git.kernel.org/netdev/net-next/c/cf35f4347ddd

You are awesome, thank you!
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