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};