LXR linux/net/dsa/tag

   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
  35static 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
  80static 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
  99const struct dsa_device_ops ksz_netdev_ops = {
 100        .xmit   = ksz_xmit,
 101        .rcv    = ksz_rcv,
 102};
 103