1// SPDX-License-Identifier: (GPL-2.0 OR MIT)
2/*
3 * net/dsa/tag_hellcreek.c - Hirschmann Hellcreek switch tag format handling
4 *
5 * Copyright (C) 2019,2020 Linutronix GmbH
6 * Author Kurt Kanzenbach <kurt@linutronix.de>
7 *
8 * Based on tag_ksz.c.
9 */
10
11#include <linux/skbuff.h>
12#include <net/dsa.h>
13
14#include "tag.h"
15
16#define HELLCREEK_NAME		"hellcreek"
17
18#define HELLCREEK_TAG_LEN	1
19
20static struct sk_buff *hellcreek_xmit(struct sk_buff *skb,
21				      struct net_device *dev)
22{
23	struct dsa_port *dp = dsa_user_to_port(dev);
24	u8 *tag;
25
26	/* Calculate checksums (if required) before adding the trailer tag to
27	 * avoid including it in calculations. That would lead to wrong
28	 * checksums after the switch strips the tag.
29	 */
30	if (skb->ip_summed == CHECKSUM_PARTIAL &&
31	    skb_checksum_help(skb))
32		return NULL;
33
34	/* Tag encoding */
35	tag  = skb_put(skb, HELLCREEK_TAG_LEN);
36	*tag = BIT(dp->index);
37
38	return skb;
39}
40
41static struct sk_buff *hellcreek_rcv(struct sk_buff *skb,
42				     struct net_device *dev)
43{
44	/* Tag decoding */
45	u8 *tag = skb_tail_pointer(skb) - HELLCREEK_TAG_LEN;
46	unsigned int port = tag[0] & 0x03;
47
48	skb->dev = dsa_conduit_find_user(dev, 0, port);
49	if (!skb->dev) {
50		netdev_warn_once(dev, "Failed to get source port: %d\n", port);
51		return NULL;
52	}
53
54	if (pskb_trim_rcsum(skb, skb->len - HELLCREEK_TAG_LEN))
55		return NULL;
56
57	dsa_default_offload_fwd_mark(skb);
58
59	return skb;
60}
61
62static const struct dsa_device_ops hellcreek_netdev_ops = {
63	.name	  = HELLCREEK_NAME,
64	.proto	  = DSA_TAG_PROTO_HELLCREEK,
65	.xmit	  = hellcreek_xmit,
66	.rcv	  = hellcreek_rcv,
67	.needed_tailroom = HELLCREEK_TAG_LEN,
68};
69
70MODULE_DESCRIPTION("DSA tag driver for Hirschmann Hellcreek TSN switches");
71MODULE_LICENSE("Dual MIT/GPL");
72MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_HELLCREEK, HELLCREEK_NAME);
73
74module_dsa_tag_driver(hellcreek_netdev_ops);
75