Re: [net-next PATCH v18 4/8] net: dsa: tag_mtk: add Airoha variant usage of this TAG

Vladimir Oltean
2025-09-17T09:35:47Z

On Mon, Sep 15, 2025 at 12:45:40PM +0200, Christian Marangi wrote:
> Add variant of the MTK TAG for Airoha Switch and comments about difference
> between Airoha AN8855 and Mediatek tag bitmap.
>
> Airoha AN8855 doesn't support controlling SA learning and Leaky VLAN
> 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.
>
> Rework the makefile, config and tag driver to better report to
> external tool (like libpcap) the usage of this variant with a dedicated
> "Airoha" name.
>
> Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
> ---
> include/net/dsa.h | 2 ++
> net/dsa/Kconfig | 11 +++++++++++
> net/dsa/Makefile | 2 +-
> net/dsa/tag_mtk.c | 36 +++++++++++++++++++++++++++++++++---
> 4 files changed, 47 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/dsa.h b/include/net/dsa.h
> index d73ea0880066..bf03493e64ab 100644
> --- a/include/net/dsa.h
> +++ b/include/net/dsa.h
> @@ -55,6 +55,7 @@ struct tc_action;
> #define DSA_TAG_PROTO_LAN937X_VALUE 27
> #define DSA_TAG_PROTO_VSC73XX_8021Q_VALUE 28
> #define DSA_TAG_PROTO_BRCM_LEGACY_FCS_VALUE 29
> +#define DSA_TAG_PROTO_AIROHA_VALUE 30
>
> enum dsa_tag_protocol {
> DSA_TAG_PROTO_NONE = DSA_TAG_PROTO_NONE_VALUE,
> @@ -69,6 +70,7 @@ enum dsa_tag_protocol {
> DSA_TAG_PROTO_KSZ9893 = DSA_TAG_PROTO_KSZ9893_VALUE,
> DSA_TAG_PROTO_LAN9303 = DSA_TAG_PROTO_LAN9303_VALUE,
> DSA_TAG_PROTO_MTK = DSA_TAG_PROTO_MTK_VALUE,
> + DSA_TAG_PROTO_AIROHA = DSA_TAG_PROTO_AIROHA_VALUE,
> DSA_TAG_PROTO_QCA = DSA_TAG_PROTO_QCA_VALUE,
> DSA_TAG_PROTO_TRAILER = DSA_TAG_PROTO_TRAILER_VALUE,
> DSA_TAG_PROTO_8021Q = DSA_TAG_PROTO_8021Q_VALUE,
> diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
> index 869cbe57162f..7d63ecda25c8 100644
> --- a/net/dsa/Kconfig
> +++ b/net/dsa/Kconfig
> @@ -98,12 +98,23 @@ config NET_DSA_TAG_EDSA
> Say Y or M if you want to enable support for tagging frames for the
> Marvell switches which use EtherType DSA headers.
>
> +config NET_DSA_TAG_MTK_COMMON
> + tristate
> +
> config NET_DSA_TAG_MTK
> tristate "Tag driver for Mediatek switches"
> + select NET_DSA_TAG_MTK_COMMON
> help
> Say Y or M if you want to enable support for tagging frames for
> Mediatek switches.
>
> +config NET_DSA_TAG_AIROHA
> + tristate "Tag driver for Airoha switches"
> + select NET_DSA_TAG_MTK_COMMON
> + help
> + Say Y or M if you want to enable support for tagging frames for
> + Airoha switches.
> +
> config NET_DSA_TAG_KSZ
> tristate "Tag driver for Microchip 8795/937x/9477/9893 families of switches"
> help
> diff --git a/net/dsa/Makefile b/net/dsa/Makefile
> index 555c07cfeb71..7aba189a715c 100644
> --- a/net/dsa/Makefile
> +++ b/net/dsa/Makefile
> @@ -27,7 +27,7 @@ obj-$(CONFIG_NET_DSA_TAG_GSWIP) += tag_gswip.o
> obj-$(CONFIG_NET_DSA_TAG_HELLCREEK) += tag_hellcreek.o
> obj-$(CONFIG_NET_DSA_TAG_KSZ) += tag_ksz.o
> obj-$(CONFIG_NET_DSA_TAG_LAN9303) += tag_lan9303.o
> -obj-$(CONFIG_NET_DSA_TAG_MTK) += tag_mtk.o
> +obj-$(CONFIG_NET_DSA_TAG_MTK_COMMON) += tag_mtk.o
> obj-$(CONFIG_NET_DSA_TAG_NONE) += tag_none.o
> obj-$(CONFIG_NET_DSA_TAG_OCELOT) += tag_ocelot.o
> obj-$(CONFIG_NET_DSA_TAG_OCELOT_8021Q) += tag_ocelot_8021q.o
> diff --git a/net/dsa/tag_mtk.c b/net/dsa/tag_mtk.c
> index b670e3c53e91..32befcbdf4be 100644
> --- a/net/dsa/tag_mtk.c
> +++ b/net/dsa/tag_mtk.c
> @@ -11,6 +11,7 @@
> #include "tag.h"
>
> #define MTK_NAME "mtk"
> +#define AIROHA_NAME "airoha"
>
> #define MTK_HDR_LEN 4
> #define MTK_HDR_XMIT_UNTAGGED 0
> @@ -18,6 +19,9 @@
> #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.
> + */
> #define MTK_HDR_XMIT_SA_DIS BIT(6)
>
> static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
> @@ -94,6 +98,7 @@ static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev)
> return skb;
> }
>
> +#if IS_ENABLED(CONFIG_NET_DSA_TAG_MTK)
> static const struct dsa_device_ops mtk_netdev_ops = {
> .name = MTK_NAME,
> .proto = DSA_TAG_PROTO_MTK,
> @@ -102,8 +107,33 @@ static const struct dsa_device_ops mtk_netdev_ops = {
> .needed_headroom = MTK_HDR_LEN,
> };
>
> -MODULE_DESCRIPTION("DSA tag driver for Mediatek switches");
> -MODULE_LICENSE("GPL");
> +DSA_TAG_DRIVER(mtk_netdev_ops);
> MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MTK, MTK_NAME);
> +#endif
>
> -module_dsa_tag_driver(mtk_netdev_ops);
> +#if IS_ENABLED(CONFIG_NET_DSA_TAG_AIROHA)
> +static const struct dsa_device_ops airoha_netdev_ops = {
> + .name = AIROHA_NAME,
> + .proto = DSA_TAG_PROTO_AIROHA,
> + .xmit = mtk_tag_xmit,
> + .rcv = mtk_tag_rcv,
> + .needed_headroom = MTK_HDR_LEN,
> +};
> +
> +DSA_TAG_DRIVER(airoha_netdev_ops);
> +MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_AIROHA, AIROHA_NAME);
> +#endif
> +
> +static struct dsa_tag_driver *dsa_tag_driver_array[] = {
> +#if IS_ENABLED(CONFIG_NET_DSA_TAG_MTK)
> + &DSA_TAG_DRIVER_NAME(mtk_netdev_ops),
> +#endif
> +#if IS_ENABLED(CONFIG_NET_DSA_TAG_AIROHA)
> + &DSA_TAG_DRIVER_NAME(airoha_netdev_ops),
> +#endif

Unless the few tens of bytes saved matter on OpenWRT, I think this is
overkill (and you went too far with my previous suggestion).
Two Kconfig options are unnecessary from a maintainance point of view
(and config NET_DSA_AN8855 isn't even selecting the correct one!).
I suggest you register both tag drivers as part of CONFIG_NET_DSA_TAG_MTK,
at least until the differences increase to justify a new option.

> +};
> +
> +module_dsa_tag_drivers(dsa_tag_driver_array);
> +
> +MODULE_DESCRIPTION("DSA tag driver for Mediatek switches");
> +MODULE_LICENSE("GPL");
> --
> 2.51.0
>