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 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 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