Commit 23049938 authored by Vincent Mailhol's avatar Vincent Mailhol Committed by Marc Kleine-Budde
Browse files

can: populate the minimum and maximum MTU values 



By populating:

  net_device->min_mtu

and

  net_device->max_mtu

the net core infrastructure will automatically:

  1. validate that the user's inputs are in range.

  2. report those min and max MTU values through the netlink
     interface.

Add can_set_default_mtu() which sets the default mtu value as well as
the minimum and maximum values. The logic for the default mtu value
remains unchanged:

  - CANFD_MTU if the device has a static CAN_CTRLMODE_FD.

  - CAN_MTU otherwise.

Call can_set_default_mtu() each time the CAN_CTRLMODE_FD is modified.
This will guarantee that the MTU value is always consistent with the
control mode flags.

With this, the checks done in can_change_mtu() become fully redundant
and will be removed in an upcoming change and it is now possible to
confirm the minimum and maximum MTU values on a physical CAN interface
by doing:

  $ ip --details link show can0

The virtual interfaces (vcan and vxcan) are not impacted by this
change.

Signed-off-by: default avatarVincent Mailhol <mailhol@kernel.org>
Link: https://patch.msgid.link/20250923-can-fix-mtu-v3-3-581bde113f52@kernel.org
[mkl: squashed https://patch.msgid.link/20250924143644.17622-2-mailhol@kernel.org

]
Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
parent 7c7da8aa

drivers/net/can/dev/dev.c

+18 −2
Original line number Diff line number Diff line
@@ -240,6 +240,8 @@ void can_setup(struct net_device *dev) 
{

	dev->type = ARPHRD_CAN;

	dev->mtu = CAN_MTU;

	dev->min_mtu = CAN_MTU;

	dev->max_mtu = CAN_MTU;

	dev->hard_header_len = 0;

	dev->addr_len = 0;

	dev->tx_queue_len = 10;
@@ -309,6 +311,21 @@ void free_candev(struct net_device *dev) 
}

EXPORT_SYMBOL_GPL(free_candev);



void can_set_default_mtu(struct net_device *dev)

{

	struct can_priv *priv = netdev_priv(dev);



	if (priv->ctrlmode & CAN_CTRLMODE_FD) {

		dev->mtu = CANFD_MTU;

		dev->min_mtu = CANFD_MTU;

		dev->max_mtu = CANFD_MTU;

	} else {

		dev->mtu = CAN_MTU;

		dev->min_mtu = CAN_MTU;

		dev->max_mtu = CAN_MTU;

	}

}



/* changing MTU and control mode for CAN/CANFD devices */

int can_change_mtu(struct net_device *dev, int new_mtu)

{
@@ -361,8 +378,7 @@ int can_set_static_ctrlmode(struct net_device *dev, u32 static_mode) 
	priv->ctrlmode = static_mode;



	/* override MTU which was set by default in can_setup()? */

	if (static_mode & CAN_CTRLMODE_FD)

		dev->mtu = CANFD_MTU;

	can_set_default_mtu(dev);



	return 0;

}

drivers/net/can/dev/netlink.c

+4 −5
Original line number Diff line number Diff line
@@ -223,17 +223,16 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[], 
		priv->ctrlmode &= ~cm->mask;

		priv->ctrlmode |= maskedflags;



		/* CAN_CTRLMODE_FD can only be set when driver supports FD */

		if (priv->ctrlmode & CAN_CTRLMODE_FD) {

			dev->mtu = CANFD_MTU;

		} else {

			dev->mtu = CAN_MTU;

		/* Wipe potential leftovers from previous CAN FD config */

		if (!(priv->ctrlmode & CAN_CTRLMODE_FD)) {

			memset(&priv->fd.data_bittiming, 0,

			       sizeof(priv->fd.data_bittiming));

			priv->ctrlmode &= ~CAN_CTRLMODE_FD_TDC_MASK;

			memset(&priv->fd.tdc, 0, sizeof(priv->fd.tdc));

		}



		can_set_default_mtu(dev);



		fd_tdc_flag_provided = cm->mask & CAN_CTRLMODE_FD_TDC_MASK;

		/* CAN_CTRLMODE_TDC_{AUTO,MANUAL} are mutually

		 * exclusive: make sure to turn the other one off

include/linux/can/dev.h

+1 −0
Original line number Diff line number Diff line
@@ -166,6 +166,7 @@ struct can_priv *safe_candev_priv(struct net_device *dev); 


int open_candev(struct net_device *dev);

void close_candev(struct net_device *dev);

void can_set_default_mtu(struct net_device *dev);

int can_change_mtu(struct net_device *dev, int new_mtu);

int __must_check can_set_static_ctrlmode(struct net_device *dev,

					 u32 static_mode);