1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Handler for Realtek 4 byte DSA switch tags 4 * Currently only supports protocol "A" found in RTL8366RB 5 * Copyright (c) 2020 Linus Walleij <linus.walleij@linaro.org> 6 * 7 * This "proprietary tag" header looks like so: 8 * 9 * ------------------------------------------------- 10 * | MAC DA | MAC SA | 0x8899 | 2 bytes tag | Type | 11 * ------------------------------------------------- 12 * 13 * The 2 bytes tag form a 16 bit big endian word. The exact 14 * meaning has been guessed from packet dumps from ingress 15 * frames. 16 */ 17 18 #include <linux/etherdevice.h> 19 #include <linux/bits.h> 20 21 #include "dsa_priv.h" 22 23 #define RTL4_A_HDR_LEN 4 24 #define RTL4_A_ETHERTYPE 0x8899 25 #define RTL4_A_PROTOCOL_SHIFT 12 26 /* 27 * 0x1 = Realtek Remote Control protocol (RRCP) 28 * 0x2/0x3 seems to be used for loopback testing 29 * 0x9 = RTL8306 DSA protocol 30 * 0xa = RTL8366RB DSA protocol 31 */ 32 #define RTL4_A_PROTOCOL_RTL8366RB 0xa 33 34 static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb, 35 struct net_device *dev) 36 { 37 struct dsa_port *dp = dsa_slave_to_port(dev); 38 __be16 *p; 39 u8 *tag; 40 u16 out; 41 42 /* Pad out to at least 60 bytes */ 43 if (unlikely(__skb_put_padto(skb, ETH_ZLEN, false))) 44 return NULL; 45 46 netdev_dbg(dev, "add realtek tag to package to port %d\n", 47 dp->index); 48 skb_push(skb, RTL4_A_HDR_LEN); 49 50 dsa_alloc_etype_header(skb, RTL4_A_HDR_LEN); 51 tag = dsa_etype_header_pos_tx(skb); 52 53 /* Set Ethertype */ 54 p = (__be16 *)tag; 55 *p = htons(RTL4_A_ETHERTYPE); 56 57 out = (RTL4_A_PROTOCOL_RTL8366RB << RTL4_A_PROTOCOL_SHIFT); 58 /* The lower bits indicate the port number */ 59 out |= BIT(dp->index); 60 61 p = (__be16 *)(tag + 2); 62 *p = htons(out); 63 64 return skb; 65 } 66 67 static struct sk_buff *rtl4a_tag_rcv(struct sk_buff *skb, 68 struct net_device *dev) 69 { 70 u16 protport; 71 __be16 *p; 72 u16 etype; 73 u8 *tag; 74 u8 prot; 75 u8 port; 76 77 if (unlikely(!pskb_may_pull(skb, RTL4_A_HDR_LEN))) 78 return NULL; 79 80 tag = dsa_etype_header_pos_rx(skb); 81 p = (__be16 *)tag; 82 etype = ntohs(*p); 83 if (etype != RTL4_A_ETHERTYPE) { 84 /* Not custom, just pass through */ 85 netdev_dbg(dev, "non-realtek ethertype 0x%04x\n", etype); 86 return skb; 87 } 88 p = (__be16 *)(tag + 2); 89 protport = ntohs(*p); 90 /* The 4 upper bits are the protocol */ 91 prot = (protport >> RTL4_A_PROTOCOL_SHIFT) & 0x0f; 92 if (prot != RTL4_A_PROTOCOL_RTL8366RB) { 93 netdev_err(dev, "unknown realtek protocol 0x%01x\n", prot); 94 return NULL; 95 } 96 port = protport & 0xff; 97 98 skb->dev = dsa_master_find_slave(dev, 0, port); 99 if (!skb->dev) { 100 netdev_dbg(dev, "could not find slave for port %d\n", port); 101 return NULL; 102 } 103 104 /* Remove RTL4 tag and recalculate checksum */ 105 skb_pull_rcsum(skb, RTL4_A_HDR_LEN); 106 107 dsa_strip_etype_header(skb, RTL4_A_HDR_LEN); 108 109 dsa_default_offload_fwd_mark(skb); 110 111 return skb; 112 } 113 114 static const struct dsa_device_ops rtl4a_netdev_ops = { 115 .name = "rtl4a", 116 .proto = DSA_TAG_PROTO_RTL4_A, 117 .xmit = rtl4a_tag_xmit, 118 .rcv = rtl4a_tag_rcv, 119 .needed_headroom = RTL4_A_HDR_LEN, 120 }; 121 module_dsa_tag_driver(rtl4a_netdev_ops); 122 123 MODULE_LICENSE("GPL"); 124 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL4_A); 125