tag_hellcreek.c

 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	u8 *tag;
24
25	/* Calculate checksums (if required) before adding the trailer tag to
26	 * avoid including it in calculations. That would lead to wrong
27	 * checksums after the switch strips the tag.
28	 */
29	if (skb->ip_summed == CHECKSUM_PARTIAL &&
30	    skb_checksum_help(skb))
31		return NULL;
32
33	/* Tag encoding */
34	tag  = skb_put(skb, HELLCREEK_TAG_LEN);
35	*tag = dsa_xmit_port_mask(skb, dev);
36
37	return skb;
38}
39
40static struct sk_buff *hellcreek_rcv(struct sk_buff *skb,
41				     struct net_device *dev)
42{
43	/* Tag decoding */
44	u8 *tag = skb_tail_pointer(skb) - HELLCREEK_TAG_LEN;
45	unsigned int port = tag[0] & 0x03;
46
47	skb->dev = dsa_conduit_find_user(dev, 0, port);
48	if (!skb->dev) {
49		netdev_warn_once(dev, "Failed to get source port: %d\n", port);
50		return NULL;
51	}
52
53	if (pskb_trim_rcsum(skb, skb->len - HELLCREEK_TAG_LEN))
54		return NULL;
55
56	dsa_default_offload_fwd_mark(skb);
57
58	return skb;
59}
60
61static const struct dsa_device_ops hellcreek_netdev_ops = {
62	.name	  = HELLCREEK_NAME,
63	.proto	  = DSA_TAG_PROTO_HELLCREEK,
64	.xmit	  = hellcreek_xmit,
65	.rcv	  = hellcreek_rcv,
66	.needed_tailroom = HELLCREEK_TAG_LEN,
67};
68
69MODULE_DESCRIPTION("DSA tag driver for Hirschmann Hellcreek TSN switches");
70MODULE_LICENSE("Dual MIT/GPL");
71MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_HELLCREEK, HELLCREEK_NAME);
72
73module_dsa_tag_driver(hellcreek_netdev_ops);