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
hellcreek_xmit(struct sk_buff * skb,struct net_device * dev)20 static struct sk_buff *hellcreek_xmit(struct sk_buff *skb,
21 struct net_device *dev)
22 {
23 struct dsa_port *dp = dsa_slave_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
hellcreek_rcv(struct sk_buff * skb,struct net_device * dev)41 static 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_master_find_slave(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
62 static 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
70 MODULE_LICENSE("Dual MIT/GPL");
71 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_HELLCREEK, HELLCREEK_NAME);
72
73 module_dsa_tag_driver(hellcreek_netdev_ops);
74