netdev - Re: [RFC net-next 2/2] net: dsa: tag_mtk: handle VLAN tag insertion on TX

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Message-Id: <20210826152737.3280662-1-dqfext@gmail.com>
Date:   Thu, 26 Aug 2021 23:27:37 +0800
From:   DENG Qingfang <dqfext@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC net-next 2/2] net: dsa: tag_mtk: handle VLAN tag insertion on TX

On Thu, Aug 26, 2021 at 05:13:26PM +0300, Vladimir Oltean wrote:
> On Thu, Aug 26, 2021 at 01:29:56PM +0800, DENG Qingfang wrote:
> > 
> > The comment says the VLAN tag need to be combined with the special tag in
> > order to perform VLAN table lookup,
> 
> It does say this.
> 
> > so we can set its destination port vector to all zeroes and the switch
> > will forward it like a data frame (TX forward offload),
> 
> And it does not say this. So this is supported after all with mt7530?
> Are you looking to add support for that?

I already run-tested that, it works, as long as there is only one bridge.

> 
> > but as we allow multiple bridges which are either VLAN-unaware or
> > VLAN-aware with the same VID, there is no way to determine the
> > destination bridge unless we maintain some VLAN translation mapping.
> 
> What does "VLAN translation mapping" mean, practically?

It's just VLAN remapping, as you stated below.

> Other drivers which cannot remap VIDs to internal VLANs just restrict a
> single VLAN-aware bridge, and potentially multiple VLAN-unaware ones.