netdev - [PATCH net-next 2/3] net: thunderbolt: Allow changing MTU of the device

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Message-ID: <20251127131521.2580237-3-mika.westerberg@linux.intel.com>
Date: Thu, 27 Nov 2025 14:15:20 +0100
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: netdev@...r.kernel.org
Cc: Yehezkel Bernat <YehezkelShB@...il.com>,
	Ian MacDonald <ian@...statz.com>,
	Salvatore Bonaccorso <carnil@...ian.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: [PATCH net-next 2/3] net: thunderbolt: Allow changing MTU of the device

In some cases it is useful to be able to use different MTU than the
default one. Especially when dealing against non-Linux networking stack.
For this reason add possibility to change the MTU of the device.

Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
---
 drivers/net/thunderbolt/main.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/thunderbolt/main.c b/drivers/net/thunderbolt/main.c
index 57b226afeb84..20bac55a3e20 100644
--- a/drivers/net/thunderbolt/main.c
+++ b/drivers/net/thunderbolt/main.c
@@ -1257,12 +1257,23 @@ static void tbnet_get_stats64(struct net_device *dev,
 	stats->rx_missed_errors = net->stats.rx_missed_errors;
 }
 
+static int tbnet_change_mtu(struct net_device *dev, int new_mtu)
+{
+	/* Keep the MTU within supported range */
+	if (new_mtu < 68 || new_mtu > (TBNET_MAX_MTU - ETH_HLEN))
+		return -EINVAL;
+
+	dev->mtu = new_mtu;
+	return 0;
+}
+
 static const struct net_device_ops tbnet_netdev_ops = {
 	.ndo_open = tbnet_open,
 	.ndo_stop = tbnet_stop,
 	.ndo_start_xmit = tbnet_start_xmit,
 	.ndo_set_mac_address = eth_mac_addr,
 	.ndo_get_stats64 = tbnet_get_stats64,
+	.ndo_change_mtu	= tbnet_change_mtu,
 };
 
 static void tbnet_generate_mac(struct net_device *dev)
-- 
2.50.1