[PATCH net-next v6 12/16] net: dsa: vsc73xx: introduce tag 8021q for vsc73xx

[Pawel Dembicki <paweldembicki@gmail.com>]

This commit introduces a new tagger based on 802.1q tagging.
It's designed for the vsc73xx driver. The VSC73xx family doesn't have
any tag support for the RGMII port, but it could be based on VLANs.

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
---
v6:
  - added missing MODULE_DESCRIPTION()
v5:
  - removed skb_vlan_tag_present(skb) checking
  - use 80 characters per line limit
v4:
  - rebase to net-next/main
v3:
  - Introduce a patch after the tagging patch split

 include/net/dsa.h           |  2 ++
 net/dsa/Kconfig             |  6 ++++
 net/dsa/Makefile            |  1 +
 net/dsa/tag_vsc73xx_8021q.c | 67 +++++++++++++++++++++++++++++++++++++
 4 files changed, 76 insertions(+)
 create mode 100644 net/dsa/tag_vsc73xx_8021q.c

diff --git a/include/net/dsa.h b/include/net/dsa.h
index 7c0da9effe4e..b79e136e4c41 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -56,6 +56,7 @@ struct phylink_link_state;
 #define DSA_TAG_PROTO_RTL8_4T_VALUE		25
 #define DSA_TAG_PROTO_RZN1_A5PSW_VALUE		26
 #define DSA_TAG_PROTO_LAN937X_VALUE		27
+#define DSA_TAG_PROTO_VSC73XX_8021Q_VALUE	28
 
 enum dsa_tag_protocol {
 	DSA_TAG_PROTO_NONE		= DSA_TAG_PROTO_NONE_VALUE,
@@ -86,6 +87,7 @@ enum dsa_tag_protocol {
 	DSA_TAG_PROTO_RTL8_4T		= DSA_TAG_PROTO_RTL8_4T_VALUE,
 	DSA_TAG_PROTO_RZN1_A5PSW	= DSA_TAG_PROTO_RZN1_A5PSW_VALUE,
 	DSA_TAG_PROTO_LAN937X		= DSA_TAG_PROTO_LAN937X_VALUE,
+	DSA_TAG_PROTO_VSC73XX_8021Q	= DSA_TAG_PROTO_VSC73XX_8021Q_VALUE,
 };
 
 struct dsa_switch;
diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
index 8e698bea99a3..e59360071c67 100644
--- a/net/dsa/Kconfig
+++ b/net/dsa/Kconfig
@@ -166,6 +166,12 @@ config NET_DSA_TAG_TRAILER
 	  Say Y or M if you want to enable support for tagging frames at
 	  with a trailed. e.g. Marvell 88E6060.
 
+config NET_DSA_TAG_VSC73XX_8021Q
+	tristate "Tag driver for Microchip/Vitesse VSC73xx family of switches, using VLAN"
+	help
+	  Say Y or M if you want to enable support for tagging frames with a
+	  custom VLAN-based header.
+
 config NET_DSA_TAG_XRS700X
 	tristate "Tag driver for XRS700x switches"
 	help
diff --git a/net/dsa/Makefile b/net/dsa/Makefile
index 8a1894a42552..555c07cfeb71 100644
--- a/net/dsa/Makefile
+++ b/net/dsa/Makefile
@@ -37,6 +37,7 @@ obj-$(CONFIG_NET_DSA_TAG_RTL8_4) += tag_rtl8_4.o
 obj-$(CONFIG_NET_DSA_TAG_RZN1_A5PSW) += tag_rzn1_a5psw.o
 obj-$(CONFIG_NET_DSA_TAG_SJA1105) += tag_sja1105.o
 obj-$(CONFIG_NET_DSA_TAG_TRAILER) += tag_trailer.o
+obj-$(CONFIG_NET_DSA_TAG_VSC73XX_8021Q) += tag_vsc73xx_8021q.o
 obj-$(CONFIG_NET_DSA_TAG_XRS700X) += tag_xrs700x.o
 
 # for tracing framework to find trace.h
diff --git a/net/dsa/tag_vsc73xx_8021q.c b/net/dsa/tag_vsc73xx_8021q.c
new file mode 100644
index 000000000000..f7bc0261d54d
--- /dev/null
+++ b/net/dsa/tag_vsc73xx_8021q.c
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/* Copyright (C) 2024 Pawel Dembicki <paweldembicki@gmail.com>
+ */
+#include <linux/dsa/8021q.h>
+
+#include "tag.h"
+#include "tag_8021q.h"
+
+#define VSC73XX_8021Q_NAME "vsc73xx-8021q"
+
+static struct sk_buff *
+vsc73xx_xmit(struct sk_buff *skb, struct net_device *netdev)
+{
+	struct dsa_port *dp = dsa_user_to_port(netdev);
+	u16 queue_mapping = skb_get_queue_mapping(skb);
+	u16 tx_vid = dsa_tag_8021q_standalone_vid(dp);
+	u8 pcp;
+
+	if (skb->offload_fwd_mark) {
+		unsigned int bridge_num = dsa_port_bridge_num_get(dp);
+		struct net_device *br = dsa_port_bridge_dev_get(dp);
+
+		if (br_vlan_enabled(br))
+			return skb;
+
+		tx_vid = dsa_tag_8021q_bridge_vid(bridge_num);
+	}
+
+	pcp = netdev_txq_to_tc(netdev, queue_mapping);
+
+	return dsa_8021q_xmit(skb, netdev, ETH_P_8021Q,
+			      ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
+}
+
+static struct sk_buff *
+vsc73xx_rcv(struct sk_buff *skb, struct net_device *netdev)
+{
+	int src_port = -1, switch_id = -1, vbid = -1, vid = -1;
+
+	dsa_8021q_rcv(skb, &src_port, &switch_id, &vbid, &vid);
+
+	skb->dev = dsa_tag_8021q_find_user(netdev, src_port, switch_id,
+					   vid, vbid);
+	if (!skb->dev) {
+		netdev_warn(netdev, "Couldn't decode source port\n");
+		return NULL;
+	}
+
+	dsa_default_offload_fwd_mark(skb);
+
+	return skb;
+}
+
+static const struct dsa_device_ops vsc73xx_8021q_netdev_ops = {
+	.name			= VSC73XX_8021Q_NAME,
+	.proto			= DSA_TAG_PROTO_VSC73XX_8021Q,
+	.xmit			= vsc73xx_xmit,
+	.rcv			= vsc73xx_rcv,
+	.needed_headroom	= VLAN_HLEN,
+	.promisc_on_conduit	= true,
+};
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("DSA tag driver for VSC73XX family of switches, using VLAN");
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_VSC73XX_8021Q, VSC73XX_8021Q_NAME);
+
+module_dsa_tag_driver(vsc73xx_8021q_netdev_ops);
-- 
2.34.1