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SubjectRe: [PATCH net-next 2/3] net: dsa: mediatek: combine MediaTek tag with VLAN tag
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On Thu, 2017-12-07 at 16:30 +0100, Andrew Lunn wrote:
> > @@ -25,20 +28,37 @@ static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
> > {
> > struct dsa_port *dp = dsa_slave_to_port(dev);
> > u8 *mtk_tag;
> > + bool is_vlan_skb = true;
>
> ..
>
> > + /* Mark tag attribute on special tag insertion to notify hardware
> > + * whether that's a combined special tag with 802.1Q header.
> > + */
> > + mtk_tag[0] = is_vlan_skb ? MTK_HDR_XMIT_TAGGED_TPID_8100 :
> > + MTK_HDR_XMIT_UNTAGGED;
> > mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
> > - mtk_tag[2] = 0;
> > - mtk_tag[3] = 0;
> > +
> > + /* Tag control information is kept for 802.1Q */
> > + if (!is_vlan_skb) {
> > + mtk_tag[2] = 0;
> > + mtk_tag[3] = 0;
> > + }
> >
> > return skb;
> > }
>
> Hi Sean
>
> So you can mark a packet for egress. What about ingress? How do you
> know the VLAN/PORT combination for packets the CPU receives? I would
> of expected a similar change to mtk_tag_rcv().
>
> Andrew

Hi, Andrew

It's unnecessary for extra handling in mtk_tag_rcv() when VLAN tag is
present since it is able to put the VLAN tag after the special tag and
then follow the existing way to parse.

Sean



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