Re: [PATCH RESEND net-next v2 2/5] net: thunderbolt: Allow changing MTU of the device

[Nikolay Aleksandrov <razor@blackwall.org>]

On 09/01/2026 14:26, Mika Westerberg wrote:
> 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@linux.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)

You can use struct net_device's min/max_mtu instead of a custom 
ndo_change_mtu.
They will be validated by dev_validate_mtu().

Cheers,
  Nik