netdev - Re: [PATCH v2 net-next 09/15] net: dsa: tag_8021q: support up to 8 VLANs per port using sub-VLANs

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Message-ID: <ebb3f4f8-0f71-094b-e997-ffcd769d6e48@gmail.com>
Date:   Mon, 11 May 2020 20:35:38 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>, andrew@...n.ch,
        vivien.didelot@...il.com
Cc:     davem@...emloft.net, kuba@...nel.org, jiri@...lanox.com,
        idosch@...sch.org, rmk+kernel@...linux.org.uk,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 net-next 09/15] net: dsa: tag_8021q: support up to 8
 VLANs per port using sub-VLANs



On 5/11/2020 6:53 AM, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
> 
> For switches that support VLAN retagging, such as sja1105, we extend
> dsa_8021q by encoding a "sub-VLAN" into the remaining 3 free bits in the
> dsa_8021q tag.
> 
> A sub-VLAN is nothing more than a number in the range 0-7, which serves
> as an index into a per-port driver lookup table. The sub-VLAN value of
> zero means that traffic is untagged (this is also backwards-compatible
> with dsa_8021q without retagging).
> 
> The switch should be configured to retag VLAN-tagged traffic that gets
> transmitted towards the CPU port (and towards the CPU only). Example:
> 
> bridge vlan add dev sw1p0 vid 100
> 
> The switch retags frames received on port 0, going to the CPU, and
> having VID 100, to the VID of 1104 (0x0450). In dsa_8021q language:
> 
>  | 11  | 10  |  9  |  8  |  7  |  6  |  5  |  4  |  3  |  2  |  1  |  0  |
>  +-----------+-----+-----------------+-----------+-----------------------+
>  |    DIR    | SVL |    SWITCH_ID    |  SUBVLAN  |          PORT         |
>  +-----------+-----+-----------------+-----------+-----------------------+
> 
> 0x0450 means:
>  - DIR = 0b01: this is an RX VLAN
>  - SUBVLAN = 0b001: this is subvlan #1
>  - SWITCH_ID = 0b001: this is switch 1 (see the name "sw1p0")
>  - PORT = 0b0000: this is port 0 (see the name "sw1p0")
> 
> The driver also remembers the "1 -> 100" mapping. In the hotpath, if the
> sub-VLAN from the tag encodes a non-untagged frame, this mapping is used
> to create a VLAN hwaccel tag, with the value of 100.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
-- 
Florian