net: usb: lan78xx: Add error handling to set_rx_max_frame_length and set_mtu

Improve error handling in `lan78xx_set_rx_max_frame_length` by:
- Checking return values from register read/write operations and
  propagating errors.
- Exiting immediately on failure to ensure proper error reporting.

In `lan78xx_change_mtu`, log errors when changing MTU fails, using `%pe`
for clear error representation.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20241204084142.1152696-9-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 33cda7f3dd12e8294b923172f7a90f2f006028f4..2d16c1fc850e93c7121a4a5e06fe3da4553103d0 100644 (file)
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2599,27 +2599,36 @@ static int lan78xx_phy_init(struct lan78xx_net *dev)
 
 static int lan78xx_set_rx_max_frame_length(struct lan78xx_net *dev, int size)
 {
-       u32 buf;
        bool rxenabled;
+       u32 buf;
+       int ret;
 
-       lan78xx_read_reg(dev, MAC_RX, &buf);
+       ret = lan78xx_read_reg(dev, MAC_RX, &buf);
+       if (ret < 0)
+               return ret;
 
        rxenabled = ((buf & MAC_RX_RXEN_) != 0);
 
        if (rxenabled) {
                buf &= ~MAC_RX_RXEN_;
-               lan78xx_write_reg(dev, MAC_RX, buf);
+               ret = lan78xx_write_reg(dev, MAC_RX, buf);
+               if (ret < 0)
+                       return ret;
        }
 
        /* add 4 to size for FCS */
        buf &= ~MAC_RX_MAX_SIZE_MASK_;
        buf |= (((size + 4) << MAC_RX_MAX_SIZE_SHIFT_) & MAC_RX_MAX_SIZE_MASK_);
 
-       lan78xx_write_reg(dev, MAC_RX, buf);
+       ret = lan78xx_write_reg(dev, MAC_RX, buf);
+       if (ret < 0)
+               return ret;
 
        if (rxenabled) {
                buf |= MAC_RX_RXEN_;
-               lan78xx_write_reg(dev, MAC_RX, buf);
+               ret = lan78xx_write_reg(dev, MAC_RX, buf);
+               if (ret < 0)
+                       return ret;
        }
 
        return 0;
@@ -2685,7 +2694,10 @@ static int lan78xx_change_mtu(struct net_device *netdev, int new_mtu)
                return ret;
 
        ret = lan78xx_set_rx_max_frame_length(dev, max_frame_len);
-       if (!ret)
+       if (ret < 0)
+               netdev_err(dev->net, "MTU changed to %d from %d failed with %pe\n",
+                          new_mtu, netdev->mtu, ERR_PTR(ret));
+       else
                WRITE_ONCE(netdev->mtu, new_mtu);
 
        usb_autopm_put_interface(dev->intf);