tag_lan9303.c
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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2017 Pengutronix, Juergen Borleis <jbe@pengutronix.de>
*/
#include <linux/dsa/lan9303.h>
#include <linux/etherdevice.h>
#include <linux/list.h>
#include <linux/slab.h>
#include "dsa_priv.h"
/* To define the outgoing port and to discover the incoming port a regular
* VLAN tag is used by the LAN9303. But its VID meaning is 'special':
*
* Dest MAC Src MAC TAG Type
* ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 | 1 2 |...
* |<------->|
* TAG:
* |<------------->|
* | 1 2 | 3 4 |
* TPID VID
* 0x8100
*
* VID bit 3 indicates a request for an ALR lookup.
*
* If VID bit 3 is zero, then bits 0 and 1 specify the destination port
* (0, 1, 2) or broadcast (3) or the source port (1, 2).
*
* VID bit 4 is used to specify if the STP port state should be overridden.
* Required when no forwarding between the external ports should happen.
*/
#define LAN9303_TAG_LEN 4
# define LAN9303_TAG_TX_USE_ALR BIT(3)
# define LAN9303_TAG_TX_STP_OVERRIDE BIT(4)
# define LAN9303_TAG_RX_IGMP BIT(3)
# define LAN9303_TAG_RX_STP BIT(4)
# define LAN9303_TAG_RX_TRAPPED_TO_CPU (LAN9303_TAG_RX_IGMP | \
LAN9303_TAG_RX_STP)
/* Decide whether to transmit using ALR lookup, or transmit directly to
* port using tag. ALR learning is performed only when using ALR lookup.
* If the two external ports are bridged and the frame is unicast,
* then use ALR lookup to allow ALR learning on CPU port.
* Otherwise transmit directly to port with STP state override.
* See also: lan9303_separate_ports() and lan9303.pdf 6.4.10.1
*/
static int lan9303_xmit_use_arl(struct dsa_port *dp, u8 *dest_addr)
{
struct lan9303 *chip = dp->ds->priv;
return chip->is_bridged && !is_multicast_ether_addr(dest_addr);
}
static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct dsa_port *dp = dsa_slave_to_port(dev);
__be16 *lan9303_tag;
u16 tag;
/* insert a special VLAN tag between the MAC addresses
* and the current ethertype field.
*/
if (skb_cow_head(skb, LAN9303_TAG_LEN) < 0) {
dev_dbg(&dev->dev,
"Cannot make room for the special tag. Dropping packet\n");
return NULL;
}
/* provide 'LAN9303_TAG_LEN' bytes additional space */
skb_push(skb, LAN9303_TAG_LEN);
/* make room between MACs and Ether-Type */
memmove(skb->data, skb->data + LAN9303_TAG_LEN, 2 * ETH_ALEN);
lan9303_tag = (__be16 *)(skb->data + 2 * ETH_ALEN);
tag = lan9303_xmit_use_arl(dp, skb->data) ?
LAN9303_TAG_TX_USE_ALR :
dp->index | LAN9303_TAG_TX_STP_OVERRIDE;
lan9303_tag[0] = htons(ETH_P_8021Q);
lan9303_tag[1] = htons(tag);
return skb;
}
static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt)
{
__be16 *lan9303_tag;
u16 lan9303_tag1;
unsigned int source_port;
if (unlikely(!pskb_may_pull(skb, LAN9303_TAG_LEN))) {
dev_warn_ratelimited(&dev->dev,
"Dropping packet, cannot pull\n");
return NULL;
}
/* '->data' points into the middle of our special VLAN tag information:
*
* ~ MAC src | 0x81 | 0x00 | 0xyy | 0xzz | ether type
* ^
* ->data
*/
lan9303_tag = (__be16 *)(skb->data - 2);
if (lan9303_tag[0] != htons(ETH_P_8021Q)) {
dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid VLAN marker\n");
return NULL;
}
lan9303_tag1 = ntohs(lan9303_tag[1]);
source_port = lan9303_tag1 & 0x3;
skb->dev = dsa_master_find_slave(dev, 0, source_port);
if (!skb->dev) {
dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid source port\n");
return NULL;
}
/* remove the special VLAN tag between the MAC addresses
* and the current ethertype field.
*/
skb_pull_rcsum(skb, 2 + 2);
memmove(skb->data - ETH_HLEN, skb->data - (ETH_HLEN + LAN9303_TAG_LEN),
2 * ETH_ALEN);
skb->offload_fwd_mark = !(lan9303_tag1 & LAN9303_TAG_RX_TRAPPED_TO_CPU);
return skb;
}
static const struct dsa_device_ops lan9303_netdev_ops = {
.name = "lan9303",
.proto = DSA_TAG_PROTO_LAN9303,
.xmit = lan9303_xmit,
.rcv = lan9303_rcv,
.overhead = LAN9303_TAG_LEN,
};
MODULE_LICENSE("GPL");
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_LAN9303);
module_dsa_tag_driver(lan9303_netdev_ops);