linux-kernel - Re: [net-next PATCH v16 10/10] net: dsa: tag_mtk: add comments about Airoha usage of this TAG

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Message-ID: <20250910082017.hjlq3664xvg5qjub@skbuf>
Date: Wed, 10 Sep 2025 11:20:17 +0300
From: Vladimir Oltean <olteanv@...il.com>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: Lee Jones <lee@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Srinivas Kandagatla <srini@...nel.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"Chester A. Unal" <chester.a.unal@...nc9.com>,
	Daniel Golle <daniel@...rotopia.org>,
	DENG Qingfang <dqfext@...il.com>,
	Sean Wang <sean.wang@...iatek.com>, Simon Horman <horms@...nel.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH v16 10/10] net: dsa: tag_mtk: add comments about
 Airoha usage of this TAG

On Tue, Sep 09, 2025 at 02:43:41AM +0200, Christian Marangi wrote:
> Add comments about difference between Airoha AN8855 and Mediatek tag
> bitmap.
> 
> Airoha AN88555 doesn't support controlling SA learning and Leaky VLAN

Is there an extra 5 in AN88555?

> from tag. Although these bits are not used (and even not defined for
> Leaky VLAN), it's worth to add comments for these difference to prevent
> any kind of regression in the future if ever these bits will be used.
> 
> Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
> ---
>  net/dsa/tag_mtk.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/dsa/tag_mtk.c b/net/dsa/tag_mtk.c
> index b670e3c53e91..ac3f956abe39 100644
> --- a/net/dsa/tag_mtk.c
> +++ b/net/dsa/tag_mtk.c
> @@ -18,6 +18,9 @@
>  #define MTK_HDR_XMIT_TAGGED_TPID_88A8	2
>  #define MTK_HDR_RECV_SOURCE_PORT_MASK	GENMASK(2, 0)
>  #define MTK_HDR_XMIT_DP_BIT_MASK	GENMASK(5, 0)
> +/* AN8855 doesn't support SA_DIS and Leaky VLAN
> + * control in tag as these bits doesn't exist.
> + */

I think it would be good to present the AN8855 tag using a different
string, so that libpcap knows it shouldn't decode these bits. The code
can be reused for now.

>  #define MTK_HDR_XMIT_SA_DIS		BIT(6)
>  
>  static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
> -- 
> 2.51.0
>