linux-kernel - [PATCH RFC 5/5] can: enable CAN XL for virtual CAN devices by default

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Message-Id: <20250918-can-fix-mtu-v1-5-471edb942295@kernel.org>
Date: Thu, 18 Sep 2025 21:59:15 +0900
From: Vincent Mailhol <mailhol@...nel.org>
To: Oliver Hartkopp <socketcan@...tkopp.net>, 
 Marc Kleine-Budde <mkl@...gutronix.de>
Cc: linux-can@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Vincent Mailhol <mailhol@...nel.org>
Subject: [PATCH RFC 5/5] can: enable CAN XL for virtual CAN devices by
 default

In commit 97edec3a11cf ("can: enable CAN FD for virtual CAN devices by
default"), vcan and vxcan default MTU was set to CANFD_MTU by default.
The reason was that users were confused on how to activate CAN FD on
virtual interfaces.

Following the introduction of CAN XL, the same logic should be
applied. Set the MTU to CANXL_MTU by default.

The users who really wish to use a Classical CAN only or a CAN FD
virtual device can do respectively:

  $ ip link set vcan0 mtu 16

or

  $ ip link set vcan0 mtu 72

to force the old behaviour.

Signed-off-by: Vincent Mailhol <mailhol@...nel.org>
---
 drivers/net/can/vcan.c  | 2 +-
 drivers/net/can/vxcan.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/vcan.c b/drivers/net/can/vcan.c
index f67e858071007acd5f34fa00a76212f1a77997a6..fdc662aea2798125b3aa373f09958363b427ced2 100644
--- a/drivers/net/can/vcan.c
+++ b/drivers/net/can/vcan.c
@@ -156,7 +156,7 @@ static const struct ethtool_ops vcan_ethtool_ops = {
 static void vcan_setup(struct net_device *dev)
 {
 	dev->type		= ARPHRD_CAN;
-	dev->mtu		= CANFD_MTU;
+	dev->mtu		= CANXL_MTU;
 	dev->hard_header_len	= 0;
 	dev->addr_len		= 0;
 	dev->tx_queue_len	= 0;
diff --git a/drivers/net/can/vxcan.c b/drivers/net/can/vxcan.c
index 99a78a75716749bf858cc78eadb41ca2588fcf94..b2c19f8c5f8e5101b8be343401afe9a4f388c4da 100644
--- a/drivers/net/can/vxcan.c
+++ b/drivers/net/can/vxcan.c
@@ -156,7 +156,7 @@ static void vxcan_setup(struct net_device *dev)
 	struct can_ml_priv *can_ml;
 
 	dev->type		= ARPHRD_CAN;
-	dev->mtu		= CANFD_MTU;
+	dev->mtu		= CANXL_MTU;
 	dev->hard_header_len	= 0;
 	dev->addr_len		= 0;
 	dev->tx_queue_len	= 0;

-- 
2.49.1