net/dsa/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 <[email protected]>
   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);