Re: [PATCH net-next v4 5/8] net: dsa: microchip: Add KSZ8463 tail tag handling

[Vladimir Oltean]

On Tue, Jan 27, 2026 at 10:06:47AM +0100, Bastien Curutchet (Schneider Electric) wrote:
> @@ -383,6 +384,74 @@ static const struct dsa_device_ops ksz9893_netdev_ops = {
>  DSA_TAG_DRIVER(ksz9893_netdev_ops);
>  MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9893, KSZ9893_NAME);
>  
> +#define KSZ8463_TAIL_TAG_PRIO		GENMASK(4, 3)
> +#define KSZ8463_TAIL_TAG_EG_PORT_M	GENMASK(2, 0)
> +
> +static struct sk_buff *ksz8463_xmit(struct sk_buff *skb,
> +				    struct net_device *dev)
> +{
> +	u16 queue_mapping = skb_get_queue_mapping(skb);
> +	u8 prio = netdev_txq_to_tc(dev, queue_mapping);
> +	struct dsa_port *dp = dsa_user_to_port(dev);
> +	u8 *tag;
> +
> +	if (skb->ip_summed == CHECKSUM_PARTIAL && skb_checksum_help(skb))
> +		return NULL;
> +
> +	tag = skb_put(skb, KSZ_INGRESS_TAG_LEN);
> +
> +	*tag = BIT(dp->index);

You're out of sync with mainline which has transitioned all
BIT(dp->index) users to dsa_xmit_port_mask(skb, dev).

To avoid this in the future please do not duplicate the ksz9893 xmit
implementation, but call a common function and use a "bool do_tstamp"
variable which is true when called from ksz9893 and false from ksz8463.

> +	*tag |= FIELD_PREP(KSZ8463_TAIL_TAG_PRIO, prio);
> +
> +	return ksz_defer_xmit(dp, skb);
> +}