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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Simon Horman , Russell King , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next v6 2/3] net: dsa: tag_yt921x: add support for Motorcomm YT921x tags Message-ID: <20250825221507.vfvnuaxs7hh2jy7d@skbuf> References: <20250824005116.2434998-1-mmyangfl@gmail.com> <20250824005116.2434998-1-mmyangfl@gmail.com> <20250824005116.2434998-3-mmyangfl@gmail.com> <20250824005116.2434998-3-mmyangfl@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250824005116.2434998-3-mmyangfl@gmail.com> <20250824005116.2434998-3-mmyangfl@gmail.com> On Sun, Aug 24, 2025 at 08:51:10AM +0800, David Yang wrote: > diff --git a/net/dsa/Makefile b/net/dsa/Makefile > index 555c07cfeb71..4b011a1d5c87 100644 > --- a/net/dsa/Makefile > +++ b/net/dsa/Makefile > @@ -39,6 +39,7 @@ 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 > +obj-$(CONFIG_NET_DSA_TAG_YT921X) += tag_yt921x.o > > # for tracing framework to find trace.h > CFLAGS_trace.o := -I$(src) > diff --git a/net/dsa/tag_yt921x.c b/net/dsa/tag_yt921x.c > new file mode 100644 > index 000000000000..ab7f97367e76 > --- /dev/null > +++ b/net/dsa/tag_yt921x.c > @@ -0,0 +1,126 @@ > +// SPDX-License-Identifier: GPL-2.0+ > +/* > + * Motorcomm YT921x Switch Extended CPU Port Tagging > + * > + * Copyright (c) 2025 David Yang > + * > + * +----+----+-------+-----+----+--------- > + * | DA | SA | TagET | Tag | ET | Payload ... > + * +----+----+-------+-----+----+--------- > + * 6 6 2 6 2 N > + * > + * Tag Ethertype: CPU_TAG_TPID_TPID (default: 0x9988) > + * Tag: > + * 2: Service VLAN Tag > + * 2: Rx Port > + * 15b: Rx Port Valid > + * 14b-11b: Rx Port > + * 10b-0b: Unknown value 0x80 > + * 2: Tx Port(s) > + * 15b: Tx Port(s) Valid > + * 10b-0b: Tx Port(s) Mask > + */ > + > +#include > +#include > +#include Why include list.h and slab.h? > + > +#include "tag.h" > + > +#define YT921X_NAME "yt921x" > + > +#define YT921X_TAG_LEN 8 > + > +#define ETH_P_YT921X 0x9988 You can add a header in include/linux/dsa/ which is shared with the switch driver, to avoid duplicate definitions. > + > +#define YT921X_TAG_PORT_EN BIT(15) > +#define YT921X_TAG_RX_PORT_M GENMASK(14, 11) > +#define YT921X_TAG_RX_CMD_M GENMASK(10, 0) > +#define YT921X_TAG_RX_CMD(x) FIELD_PREP(YT921X_TAG_RX_CMD_M, (x)) > +#define YT921X_TAG_RX_CMD_UNK_NORMAL 0x80 > +#define YT921X_TAG_TX_PORTS_M GENMASK(10, 0) > +#define YT921X_TAG_TX_PORTn(port) BIT(port) > + > +static struct sk_buff * > +yt921x_tag_xmit(struct sk_buff *skb, struct net_device *netdev) > +{ > + struct dsa_port *dp = dsa_user_to_port(netdev); > + unsigned int port = dp->index; > + __be16 *tag; > + u16 tx; > + > + skb_push(skb, YT921X_TAG_LEN); > + dsa_alloc_etype_header(skb, YT921X_TAG_LEN); > + > + tag = dsa_etype_header_pos_tx(skb); > + > + /* We might use yt921x_priv::tag_eth_p, but > + * 1. CPU_TAG_TPID could be configured anyway; > + * 2. Are you using the right chip? The tag format sort of becomes fixed ABI as soon as user space is able to run "cat /sys/class/net/eth0/dsa/tagging", see "yt921x", and record it to a pcap file. Unless the EtherType bears some other meaning rather than being a fixed value, then if you change it later to some other value than 0x9988, you'd better also change the protocol name to distinguish it from "yt921x". Also, you can _not_ use yt921x_priv :: tag_eth_p, because doing so would assume that typeof(ds->priv) == struct yt921x_priv. In principle we would like to be able to run the tagging protocols on the dsa_loop driver as well, which can be attached to any network interface. Very few, if any, tagging protocol drivers don't work on dsa_loop. > + */ > + tag[0] = htons(ETH_P_YT921X); > + /* Service VLAN tag not used */ > + tag[1] = 0; > + tag[2] = 0; > + tx = YT921X_TAG_PORT_EN | YT921X_TAG_TX_PORTn(port); > + tag[3] = htons(tx); > + > + /* Now tell the conduit network device about the desired output queue > + * as well > + */ > + skb_set_queue_mapping(skb, port); This is generally used for integrated DSA switches, for lossless backpressure during CPU transmission, where the conduit interface driver is known, and has set up its queues in a special way, as a result of the fact that it is attached to a known DSA switch (made by the same vendor). What do you need it for, in a discrete MDIO-controlled switch? > + > + return skb; > +} > + > +static struct sk_buff * > +yt921x_tag_rcv(struct sk_buff *skb, struct net_device *netdev) > +{ > + unsigned int port; > + __be16 *tag; > + u16 rx; > + > + if (unlikely(!pskb_may_pull(skb, YT921X_TAG_LEN))) > + return NULL; > + > + tag = (__be16 *)skb->data; Use dsa_etype_header_pos_rx() and validate the CPU_TAG_TPID_TPID as well. > + > + /* Locate which port this is coming from */ > + rx = ntohs(tag[1]); > + if (unlikely((rx & YT921X_TAG_PORT_EN) == 0)) { > + dev_warn_ratelimited(&netdev->dev, > + "Unexpected rx tag 0x%04x\n", rx); > + return NULL; > + } > + > + port = FIELD_GET(YT921X_TAG_RX_PORT_M, rx); > + skb->dev = dsa_conduit_find_user(netdev, 0, port); > + if (unlikely(!skb->dev)) { > + dev_warn_ratelimited(&netdev->dev, > + "Couldn't decode source port %u\n", port); > + return NULL; > + } > + > + /* Remove YT921x tag and update checksum */ > + skb_pull_rcsum(skb, YT921X_TAG_LEN); > + > + dsa_default_offload_fwd_mark(skb); > + > + dsa_strip_etype_header(skb, YT921X_TAG_LEN); > + > + return skb; > +} > + > +static const struct dsa_device_ops yt921x_netdev_ops = { > + .name = YT921X_NAME, > + .proto = DSA_TAG_PROTO_YT921X, > + .xmit = yt921x_tag_xmit, > + .rcv = yt921x_tag_rcv, > + .needed_headroom = YT921X_TAG_LEN, > +}; > + > +MODULE_DESCRIPTION("DSA tag driver for Motorcomm YT921x switches"); > +MODULE_LICENSE("GPL"); > +MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_YT921X, YT921X_NAME); > + > +module_dsa_tag_driver(yt921x_netdev_ops); > -- > 2.50.1 >