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// SPDX-License-Identifier: GPL-2.0
/*
* Handler for Realtek 4 byte DSA switch tags
* Currently only supports protocol "A" found in RTL8366RB
* Copyright (c) 2020 Linus Walleij <linus.walleij@linaro.org>
*
* This "proprietary tag" header looks like so:
*
* -------------------------------------------------
* | MAC DA | MAC SA | 0x8899 | 2 bytes tag | Type |
* -------------------------------------------------
*
* The 2 bytes tag form a 16 bit big endian word. The exact
* meaning has been guessed from packet dumps from ingress
* frames.
*/
#include <linux/etherdevice.h>
#include <linux/bits.h>
#include "tag.h"
#define RTL4_A_NAME "rtl4a"
#define RTL4_A_HDR_LEN 4
#define RTL4_A_PROTOCOL_SHIFT 12
/*
* 0x1 = Realtek Remote Control protocol (RRCP)
* 0x2/0x3 seems to be used for loopback testing
* 0x9 = RTL8306 DSA protocol
* 0xa = RTL8366RB DSA protocol
*/
#define RTL4_A_PROTOCOL_RTL8366RB 0xa
static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb,
struct net_device *dev)
{
struct dsa_port *dp = dsa_user_to_port(dev);
__be16 *p;
u8 *tag;
u16 out;
/* Pad out to at least 60 bytes */
if (unlikely(eth_skb_pad(skb)))
return NULL;
netdev_dbg(dev, "add realtek tag to package to port %d\n",
dp->index);
skb_push(skb, RTL4_A_HDR_LEN);
dsa_alloc_etype_header(skb, RTL4_A_HDR_LEN);
tag = dsa_etype_header_pos_tx(skb);
/* Set Ethertype */
p = (__be16 *)tag;
*p = htons(ETH_P_REALTEK);
out = (RTL4_A_PROTOCOL_RTL8366RB << RTL4_A_PROTOCOL_SHIFT);
/* The lower bits indicate the port number */
out |= dsa_xmit_port_mask(skb, dev);
p = (__be16 *)(tag + 2);
*p = htons(out);
return skb;
}
static struct sk_buff *rtl4a_tag_rcv(struct sk_buff *skb,
struct net_device *dev)
{
u16 protport;
__be16 *p;
u16 etype;
u8 *tag;
u8 prot;
u8 port;
if (unlikely(!pskb_may_pull(skb, RTL4_A_HDR_LEN))) {
kfree_skb(skb);
return NULL;
}
tag = dsa_etype_header_pos_rx(skb);
p = (__be16 *)tag;
etype = ntohs(*p);
if (etype != ETH_P_REALTEK) {
/* Not custom, just pass through */
netdev_dbg(dev, "non-realtek ethertype 0x%04x\n", etype);
return skb;
}
p = (__be16 *)(tag + 2);
protport = ntohs(*p);
/* The 4 upper bits are the protocol */
prot = (protport >> RTL4_A_PROTOCOL_SHIFT) & 0x0f;
if (prot != RTL4_A_PROTOCOL_RTL8366RB) {
netdev_err(dev, "unknown realtek protocol 0x%01x\n", prot);
kfree_skb(skb);
return NULL;
}
port = protport & 0xff;
skb->dev = dsa_conduit_find_user(dev, 0, port);
if (!skb->dev) {
netdev_dbg(dev, "could not find user for port %d\n", port);
kfree_skb(skb);
return NULL;
}
/* Remove RTL4 tag and recalculate checksum */
skb_pull_rcsum(skb, RTL4_A_HDR_LEN);
dsa_strip_etype_header(skb, RTL4_A_HDR_LEN);
dsa_default_offload_fwd_mark(skb);
return skb;
}
static const struct dsa_device_ops rtl4a_netdev_ops = {
.name = RTL4_A_NAME,
.proto = DSA_TAG_PROTO_RTL4_A,
.xmit = rtl4a_tag_xmit,
.rcv = rtl4a_tag_rcv,
.needed_headroom = RTL4_A_HDR_LEN,
};
module_dsa_tag_driver(rtl4a_netdev_ops);
MODULE_DESCRIPTION("DSA tag driver for Realtek 4 byte protocol A tags");
MODULE_LICENSE("GPL");
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL4_A, RTL4_A_NAME);
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