// SPDX-License-Identifier: GPL-2.0+

  /*
   * Broadcom tag support
   *
   * Copyright (C) 2014 Broadcom Corporation

   */
  
  #include <linux/etherdevice.h>
  #include <linux/list.h>

  #include <linux/slab.h>

  #include "dsa_priv.h"
  
  /* This tag length is 4 bytes, older ones were 6 bytes, we do not
   * handle them
   */
  #define BRCM_TAG_LEN	4
  
  /* Tag is constructed and desconstructed using byte by byte access
   * because the tag is placed after the MAC Source Address, which does
   * not make it 4-bytes aligned, so this might cause unaligned accesses
   * on most systems where this is used.
   */
  
  /* Ingress and egress opcodes */
  #define BRCM_OPCODE_SHIFT	5
  #define BRCM_OPCODE_MASK	0x7
  
  /* Ingress fields */
  /* 1st byte in the tag */
  #define BRCM_IG_TC_SHIFT	2
  #define BRCM_IG_TC_MASK		0x7
  /* 2nd byte in the tag */
  #define BRCM_IG_TE_MASK		0x3
  #define BRCM_IG_TS_SHIFT	7
  /* 3rd byte in the tag */
  #define BRCM_IG_DSTMAP2_MASK	1
  #define BRCM_IG_DSTMAP1_MASK	0xff
  
  /* Egress fields */
  
  /* 2nd byte in the tag */
  #define BRCM_EG_CID_MASK	0xff
  
  /* 3rd byte in the tag */
  #define BRCM_EG_RC_MASK		0xff
  #define  BRCM_EG_RC_RSVD	(3 << 6)
  #define  BRCM_EG_RC_EXCEPTION	(1 << 5)
  #define  BRCM_EG_RC_PROT_SNOOP	(1 << 4)
  #define  BRCM_EG_RC_PROT_TERM	(1 << 3)
  #define  BRCM_EG_RC_SWITCH	(1 << 2)
  #define  BRCM_EG_RC_MAC_LEARN	(1 << 1)
  #define  BRCM_EG_RC_MIRROR	(1 << 0)
  #define BRCM_EG_TC_SHIFT	5
  #define BRCM_EG_TC_MASK		0x7
  #define BRCM_EG_PID_MASK	0x1f

  #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM) || \
  	IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_PREPEND)

  static struct sk_buff *brcm_tag_xmit_ll(struct sk_buff *skb,
  					struct net_device *dev,
  					unsigned int offset)

  {

  	struct dsa_port *dp = dsa_slave_to_port(dev);

  	u16 queue = skb_get_queue_mapping(skb);

  	u8 *brcm_tag;

  	if (skb_cow_head(skb, BRCM_TAG_LEN) < 0)

  		return NULL;

  	/* The Ethernet switch we are interfaced with needs packets to be at
  	 * least 64 bytes (including FCS) otherwise they will be discarded when
  	 * they enter the switch port logic. When Broadcom tags are enabled, we
  	 * need to make sure that packets are at least 68 bytes
  	 * (including FCS and tag) because the length verification is done after
  	 * the Broadcom tag is stripped off the ingress packet.
  	 *
  	 * Let dsa_slave_xmit() free the SKB
  	 */
  	if (__skb_put_padto(skb, ETH_ZLEN + BRCM_TAG_LEN, false))
  		return NULL;

  	skb_push(skb, BRCM_TAG_LEN);

  	if (offset)
  		memmove(skb->data, skb->data + BRCM_TAG_LEN, offset);

  	brcm_tag = skb->data + offset;

  
  	/* Set the ingress opcode, traffic class, tag enforcment is
  	 * deprecated
  	 */
  	brcm_tag[0] = (1 << BRCM_OPCODE_SHIFT) |

  		       ((queue & BRCM_IG_TC_MASK) << BRCM_IG_TC_SHIFT);

  	brcm_tag[1] = 0;
  	brcm_tag[2] = 0;

  	if (dp->index == 8)

  		brcm_tag[2] = BRCM_IG_DSTMAP2_MASK;

  	brcm_tag[3] = (1 << dp->index) & BRCM_IG_DSTMAP1_MASK;

  	/* Now tell the master network device about the desired output queue
  	 * as well
  	 */

  	skb_set_queue_mapping(skb, BRCM_TAG_SET_PORT_QUEUE(dp->index, queue));

  	return skb;

  }

  static struct sk_buff *brcm_tag_rcv_ll(struct sk_buff *skb,
  				       struct net_device *dev,
  				       struct packet_type *pt,
  				       unsigned int offset)

  {

  	int source_port;
  	u8 *brcm_tag;

  	if (unlikely(!pskb_may_pull(skb, BRCM_TAG_LEN)))

  		return NULL;

  	brcm_tag = skb->data - offset;

  
  	/* The opcode should never be different than 0b000 */
  	if (unlikely((brcm_tag[0] >> BRCM_OPCODE_SHIFT) & BRCM_OPCODE_MASK))

  		return NULL;

  
  	/* We should never see a reserved reason code without knowing how to
  	 * handle it
  	 */

  	if (unlikely(brcm_tag[2] & BRCM_EG_RC_RSVD))

  		return NULL;

  
  	/* Locate which port this is coming from */
  	source_port = brcm_tag[3] & BRCM_EG_PID_MASK;

  	skb->dev = dsa_master_find_slave(dev, 0, source_port);

  	if (!skb->dev)

  		return NULL;

  
  	/* Remove Broadcom tag and update checksum */
  	skb_pull_rcsum(skb, BRCM_TAG_LEN);

  	skb->offload_fwd_mark = 1;

  	return skb;
  }

  #endif

  #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM)

  static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb,
  				     struct net_device *dev)
  {
  	/* Build the tag after the MAC Source Address */
  	return brcm_tag_xmit_ll(skb, dev, 2 * ETH_ALEN);
  }

  static struct sk_buff *brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev,
  				    struct packet_type *pt)
  {
  	struct sk_buff *nskb;
  
  	/* skb->data points to the EtherType, the tag is right before it */
  	nskb = brcm_tag_rcv_ll(skb, dev, pt, 2);
  	if (!nskb)
  		return nskb;

  	/* Move the Ethernet DA and SA */

  	memmove(nskb->data - ETH_HLEN,
  		nskb->data - ETH_HLEN - BRCM_TAG_LEN,

  		2 * ETH_ALEN);

  	return nskb;

  }

  static const struct dsa_device_ops brcm_netdev_ops = {

  	.name	= "brcm",

  	.proto	= DSA_TAG_PROTO_BRCM,

  	.xmit	= brcm_tag_xmit,
  	.rcv	= brcm_tag_rcv,

  	.overhead = BRCM_TAG_LEN,

  };

  DSA_TAG_DRIVER(brcm_netdev_ops);

  MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_BRCM);

  #endif

  #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_PREPEND)

  static struct sk_buff *brcm_tag_xmit_prepend(struct sk_buff *skb,
  					     struct net_device *dev)
  {
  	/* tag is prepended to the packet */
  	return brcm_tag_xmit_ll(skb, dev, 0);
  }
  
  static struct sk_buff *brcm_tag_rcv_prepend(struct sk_buff *skb,
  					    struct net_device *dev,
  					    struct packet_type *pt)
  {
  	/* tag is prepended to the packet */
  	return brcm_tag_rcv_ll(skb, dev, pt, ETH_HLEN);
  }

  static const struct dsa_device_ops brcm_prepend_netdev_ops = {

  	.name	= "brcm-prepend",

  	.proto	= DSA_TAG_PROTO_BRCM_PREPEND,

  	.xmit	= brcm_tag_xmit_prepend,
  	.rcv	= brcm_tag_rcv_prepend,

  	.overhead = BRCM_TAG_LEN,

  };

  DSA_TAG_DRIVER(brcm_prepend_netdev_ops);

  MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_BRCM_PREPEND);

  #endif

  
  static struct dsa_tag_driver *dsa_tag_driver_array[] =	{
  #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM)
  	&DSA_TAG_DRIVER_NAME(brcm_netdev_ops),
  #endif
  #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_PREPEND)
  	&DSA_TAG_DRIVER_NAME(brcm_prepend_netdev_ops),
  #endif
  };
  
  module_dsa_tag_drivers(dsa_tag_driver_array);
  
  MODULE_LICENSE("GPL");