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