net/dsa/tag_ksz.c

   1 /*
   2  * net/dsa/tag_ksz.c - Microchip KSZ Switch tag format handling
   3  * Copyright (c) 2017 Microchip Technology
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  */
  10
  11 #include <linux/etherdevice.h>
  12 #include <linux/list.h>
  13 #include <linux/slab.h>
  14 #include <net/dsa.h>
  15 #include "dsa_priv.h"
  16
  17 /* For Ingress (Host -> KSZ), 2 bytes are added before FCS.
  18  * ---------------------------------------------------------------------------
  19  * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|tag1(1byte)|FCS(4bytes)
  20  * ---------------------------------------------------------------------------
  21  * tag0 : Prioritization (not used now)
  22  * tag1 : each bit represents port (eg, 0x01=port1, 0x02=port2, 0x10=port5)
  23  *
  24  * For Egress (KSZ -> Host), 1 byte is added before FCS.
  25  * ---------------------------------------------------------------------------
  26  * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|FCS(4bytes)
  27  * ---------------------------------------------------------------------------
  28  * tag0 : zero-based value represents port
  29  *        (eg, 0x00=port1, 0x02=port3, 0x06=port7)
  30  */
  31
  32 #define KSZ_INGRESS_TAG_LEN     2
  33 #define KSZ_EGRESS_TAG_LEN      1
  34
  35 static struct sk_buff *ksz_xmit(struct sk_buff *skb, struct net_device *dev)
  36 {
  37         struct dsa_port *dp = dsa_slave_to_port(dev);
  38         struct sk_buff *nskb;
  39         int padlen;
  40         u8 *tag;
  41
  42         padlen = (skb->len >= ETH_ZLEN) ? 0 : ETH_ZLEN - skb->len;
  43
  44         if (skb_tailroom(skb) >= padlen + KSZ_INGRESS_TAG_LEN) {
  45                 /* Let dsa_slave_xmit() free skb */
  46                 if (__skb_put_padto(skb, skb->len + padlen, false))
  47                         return NULL;
  48
  49                 nskb = skb;
  50         } else {
  51                 nskb = alloc_skb(NET_IP_ALIGN + skb->len +
  52                                  padlen + KSZ_INGRESS_TAG_LEN, GFP_ATOMIC);
  53                 if (!nskb)
  54                         return NULL;
  55                 skb_reserve(nskb, NET_IP_ALIGN);
  56
  57                 skb_reset_mac_header(nskb);
  58                 skb_set_network_header(nskb,
  59                                        skb_network_header(skb) - skb->head);
  60                 skb_set_transport_header(nskb,
  61                                          skb_transport_header(skb) - skb->head);
  62                 skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
  63
  64                 /* Let skb_put_padto() free nskb, and let dsa_slave_xmit() free
  65                  * skb
  66                  */
  67                 if (skb_put_padto(nskb, nskb->len + padlen))
  68                         return NULL;
  69
  70                 consume_skb(skb);
  71         }
  72
  73         tag = skb_put(nskb, KSZ_INGRESS_TAG_LEN);
  74         tag[0] = 0;
  75         tag[1] = 1 << dp->index; /* destination port */
  76
  77         return nskb;
  78 }
  79
  80 static struct sk_buff *ksz_rcv(struct sk_buff *skb, struct net_device *dev,
  81                                struct packet_type *pt)
  82 {
  83         u8 *tag;
  84         int source_port;
  85
  86         tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN;
  87
  88         source_port = tag[0] & 7;
  89
  90         skb->dev = dsa_master_find_slave(dev, 0, source_port);
  91         if (!skb->dev)
  92                 return NULL;
  93
  94         pskb_trim_rcsum(skb, skb->len - KSZ_EGRESS_TAG_LEN);
  95
  96         return skb;
  97 }
  98
  99 const struct dsa_device_ops ksz_netdev_ops = {
 100         .xmit   = ksz_xmit,
 101         .rcv    = ksz_rcv,
 102 };