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_slave_priv *p = netdev_priv(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                 nskb = skb;
  46         } else {
  47                 nskb = alloc_skb(NET_IP_ALIGN + skb->len +
  48                                  padlen + KSZ_INGRESS_TAG_LEN, GFP_ATOMIC);
  49                 if (!nskb)
  50                         return NULL;
  51                 skb_reserve(nskb, NET_IP_ALIGN);
  52
  53                 skb_reset_mac_header(nskb);
  54                 skb_set_network_header(nskb,
  55                                        skb_network_header(skb) - skb->head);
  56                 skb_set_transport_header(nskb,
  57                                          skb_transport_header(skb) - skb->head);
  58                 skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
  59                 kfree_skb(skb);
  60         }
  61
  62         /* skb is freed when it fails */
  63         if (skb_put_padto(nskb, nskb->len + padlen))
  64                 return NULL;
  65
  66         tag = skb_put(nskb, KSZ_INGRESS_TAG_LEN);
  67         tag[0] = 0;
  68         tag[1] = 1 << p->dp->index; /* destination port */
  69
  70         return nskb;
  71 }
  72
  73 static struct sk_buff *ksz_rcv(struct sk_buff *skb, struct net_device *dev,
  74                                struct packet_type *pt,
  75                                struct net_device *orig_dev)
  76 {
  77         struct dsa_switch_tree *dst = dev->dsa_ptr;
  78         struct dsa_port *cpu_dp = dsa_get_cpu_port(dst);
  79         struct dsa_switch *ds = cpu_dp->ds;
  80         u8 *tag;
  81         int source_port;
  82
  83         tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN;
  84
  85         source_port = tag[0] & 7;
  86         if (source_port >= ds->num_ports || !ds->ports[source_port].netdev)
  87                 return NULL;
  88
  89         pskb_trim_rcsum(skb, skb->len - KSZ_EGRESS_TAG_LEN);
  90
  91         skb->dev = ds->ports[source_port].netdev;
  92
  93         return skb;
  94 }
  95
  96 const struct dsa_device_ops ksz_netdev_ops = {
  97         .xmit   = ksz_xmit,
  98         .rcv    = ksz_rcv,
  99 };