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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* DSA Special Tag for MaxLinear 862xx switch chips
*
* Copyright (C) 2025 Daniel Golle <daniel@makrotopia.org>
* Copyright (C) 2024 MaxLinear Inc.
*/
#include <linux/bitops.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <net/dsa.h>
#include "tag.h"
#define MXL862_NAME "mxl862xx"
#define MXL862_HEADER_LEN 8
/* Word 0 -> EtherType */
/* Word 2 */
#define MXL862_SUBIF_ID GENMASK(4, 0)
/* Word 3 */
#define MXL862_IGP_EGP GENMASK(3, 0)
static struct sk_buff *mxl862_tag_xmit(struct sk_buff *skb,
struct net_device *dev)
{
struct dsa_port *dp = dsa_user_to_port(dev);
struct dsa_port *cpu_dp = dp->cpu_dp;
unsigned int cpu_port, sub_interface;
__be16 *mxl862_tag;
cpu_port = cpu_dp->index;
/* target port sub-interface ID relative to the CPU port */
sub_interface = dp->index + 16 - cpu_port;
/* provide additional space 'MXL862_HEADER_LEN' bytes */
skb_push(skb, MXL862_HEADER_LEN);
/* shift MAC address to the beginning of the enlarged buffer,
* releasing the space required for DSA tag (between MAC address and
* Ethertype)
*/
dsa_alloc_etype_header(skb, MXL862_HEADER_LEN);
/* special tag ingress (from the perspective of the switch) */
mxl862_tag = dsa_etype_header_pos_tx(skb);
mxl862_tag[0] = htons(ETH_P_MXLGSW);
mxl862_tag[1] = 0;
mxl862_tag[2] = htons(FIELD_PREP(MXL862_SUBIF_ID, sub_interface));
mxl862_tag[3] = htons(FIELD_PREP(MXL862_IGP_EGP, cpu_port));
return skb;
}
static struct sk_buff *mxl862_tag_rcv(struct sk_buff *skb,
struct net_device *dev)
{
__be16 *mxl862_tag;
int port;
if (unlikely(!pskb_may_pull(skb, MXL862_HEADER_LEN))) {
dev_warn_ratelimited(&dev->dev, "Cannot pull SKB, packet dropped\n");
return NULL;
}
mxl862_tag = dsa_etype_header_pos_rx(skb);
if (unlikely(mxl862_tag[0] != htons(ETH_P_MXLGSW))) {
dev_warn_ratelimited(&dev->dev,
"Invalid special tag marker, packet dropped, tag: %8ph\n",
mxl862_tag);
return NULL;
}
/* Get source port information */
port = FIELD_GET(MXL862_IGP_EGP, ntohs(mxl862_tag[3]));
skb->dev = dsa_conduit_find_user(dev, 0, port);
if (unlikely(!skb->dev)) {
dev_warn_ratelimited(&dev->dev,
"Invalid source port, packet dropped, tag: %8ph\n",
mxl862_tag);
return NULL;
}
if (likely(!is_link_local_ether_addr(eth_hdr(skb)->h_dest)))
dsa_default_offload_fwd_mark(skb);
/* remove the MxL862xx special tag between the MAC addresses and the
* current ethertype field.
*/
skb_pull_rcsum(skb, MXL862_HEADER_LEN);
dsa_strip_etype_header(skb, MXL862_HEADER_LEN);
return skb;
}
static const struct dsa_device_ops mxl862_netdev_ops = {
.name = MXL862_NAME,
.proto = DSA_TAG_PROTO_MXL862,
.xmit = mxl862_tag_xmit,
.rcv = mxl862_tag_rcv,
.needed_headroom = MXL862_HEADER_LEN,
};
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MXL862, MXL862_NAME);
MODULE_DESCRIPTION("DSA tag driver for MaxLinear MxL862xx switches");
MODULE_LICENSE("GPL");
module_dsa_tag_driver(mxl862_netdev_ops);
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