/*
   * Copyright Gavin Shan, IBM Corporation 2016.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   */
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/etherdevice.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>
  
  #include <net/ncsi.h>
  #include <net/net_namespace.h>
  #include <net/sock.h>
  
  #include "internal.h"
  #include "ncsi-pkt.h"
  
  u32 ncsi_calculate_checksum(unsigned char *data, int len)
  {
  	u32 checksum = 0;
  	int i;
  
  	for (i = 0; i < len; i += 2)
  		checksum += (((u32)data[i] << 8) | data[i + 1]);
  
  	checksum = (~checksum + 1);
  	return checksum;
  }
  
  /* This function should be called after the data area has been
   * populated completely.
   */
  static void ncsi_cmd_build_header(struct ncsi_pkt_hdr *h,
  				  struct ncsi_cmd_arg *nca)
  {
  	u32 checksum;
  	__be32 *pchecksum;
  
  	h->mc_id        = 0;
  	h->revision     = NCSI_PKT_REVISION;
  	h->reserved     = 0;
  	h->id           = nca->id;
  	h->type         = nca->type;
  	h->channel      = NCSI_TO_CHANNEL(nca->package,
  					  nca->channel);
  	h->length       = htons(nca->payload);
  	h->reserved1[0] = 0;
  	h->reserved1[1] = 0;
  
  	/* Fill with calculated checksum */
  	checksum = ncsi_calculate_checksum((unsigned char *)h,
  					   sizeof(*h) + nca->payload);
  	pchecksum = (__be32 *)((void *)h + sizeof(struct ncsi_pkt_hdr) +
  		    nca->payload);
  	*pchecksum = htonl(checksum);
  }
  
  static int ncsi_cmd_handler_default(struct sk_buff *skb,
  				    struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_pkt *cmd;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static int ncsi_cmd_handler_sp(struct sk_buff *skb,
  			       struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_sp_pkt *cmd;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	cmd->hw_arbitration = nca->bytes[0];
  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static int ncsi_cmd_handler_dc(struct sk_buff *skb,
  			       struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_dc_pkt *cmd;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	cmd->ald = nca->bytes[0];
  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static int ncsi_cmd_handler_rc(struct sk_buff *skb,
  			       struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_rc_pkt *cmd;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static int ncsi_cmd_handler_ae(struct sk_buff *skb,
  			       struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_ae_pkt *cmd;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	cmd->mc_id = nca->bytes[0];
  	cmd->mode = htonl(nca->dwords[1]);
  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static int ncsi_cmd_handler_sl(struct sk_buff *skb,
  			       struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_sl_pkt *cmd;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	cmd->mode = htonl(nca->dwords[0]);
  	cmd->oem_mode = htonl(nca->dwords[1]);
  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static int ncsi_cmd_handler_svf(struct sk_buff *skb,
  				struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_svf_pkt *cmd;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	cmd->vlan = htons(nca->words[1]);
  	cmd->index = nca->bytes[6];
  	cmd->enable = nca->bytes[7];

  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static int ncsi_cmd_handler_ev(struct sk_buff *skb,
  			       struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_ev_pkt *cmd;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	cmd->mode = nca->bytes[3];

  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static int ncsi_cmd_handler_sma(struct sk_buff *skb,
  				struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_sma_pkt *cmd;
  	int i;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	for (i = 0; i < 6; i++)
  		cmd->mac[i] = nca->bytes[i];
  	cmd->index = nca->bytes[6];
  	cmd->at_e = nca->bytes[7];
  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static int ncsi_cmd_handler_ebf(struct sk_buff *skb,
  				struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_ebf_pkt *cmd;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	cmd->mode = htonl(nca->dwords[0]);
  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static int ncsi_cmd_handler_egmf(struct sk_buff *skb,
  				 struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_egmf_pkt *cmd;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	cmd->mode = htonl(nca->dwords[0]);
  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static int ncsi_cmd_handler_snfc(struct sk_buff *skb,
  				 struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_cmd_snfc_pkt *cmd;

  	cmd = skb_put_zero(skb, sizeof(*cmd));

  	cmd->mode = nca->bytes[0];
  	ncsi_cmd_build_header(&cmd->cmd.common, nca);
  
  	return 0;
  }
  
  static struct ncsi_cmd_handler {
  	unsigned char type;
  	int           payload;
  	int           (*handler)(struct sk_buff *skb,
  				 struct ncsi_cmd_arg *nca);
  } ncsi_cmd_handlers[] = {
  	{ NCSI_PKT_CMD_CIS,    0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_SP,     4, ncsi_cmd_handler_sp      },
  	{ NCSI_PKT_CMD_DP,     0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_EC,     0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_DC,     4, ncsi_cmd_handler_dc      },
  	{ NCSI_PKT_CMD_RC,     4, ncsi_cmd_handler_rc      },
  	{ NCSI_PKT_CMD_ECNT,   0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_DCNT,   0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_AE,     8, ncsi_cmd_handler_ae      },
  	{ NCSI_PKT_CMD_SL,     8, ncsi_cmd_handler_sl      },
  	{ NCSI_PKT_CMD_GLS,    0, ncsi_cmd_handler_default },

  	{ NCSI_PKT_CMD_SVF,    8, ncsi_cmd_handler_svf     },

  	{ NCSI_PKT_CMD_EV,     4, ncsi_cmd_handler_ev      },
  	{ NCSI_PKT_CMD_DV,     0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_SMA,    8, ncsi_cmd_handler_sma     },
  	{ NCSI_PKT_CMD_EBF,    4, ncsi_cmd_handler_ebf     },
  	{ NCSI_PKT_CMD_DBF,    0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_EGMF,   4, ncsi_cmd_handler_egmf    },
  	{ NCSI_PKT_CMD_DGMF,   0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_SNFC,   4, ncsi_cmd_handler_snfc    },
  	{ NCSI_PKT_CMD_GVI,    0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_GC,     0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_GP,     0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_GCPS,   0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_GNS,    0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_GNPTS,  0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_GPS,    0, ncsi_cmd_handler_default },
  	{ NCSI_PKT_CMD_OEM,    0, NULL                     },
  	{ NCSI_PKT_CMD_PLDM,   0, NULL                     },
  	{ NCSI_PKT_CMD_GPUUID, 0, ncsi_cmd_handler_default }
  };
  
  static struct ncsi_request *ncsi_alloc_command(struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_dev_priv *ndp = nca->ndp;
  	struct ncsi_dev *nd = &ndp->ndev;
  	struct net_device *dev = nd->dev;
  	int hlen = LL_RESERVED_SPACE(dev);
  	int tlen = dev->needed_tailroom;
  	int len = hlen + tlen;
  	struct sk_buff *skb;
  	struct ncsi_request *nr;

  	nr = ncsi_alloc_request(ndp, nca->req_flags);

  	if (!nr)
  		return NULL;
  
  	/* NCSI command packet has 16-bytes header, payload, 4 bytes checksum.
  	 * The packet needs padding if its payload is less than 26 bytes to
  	 * meet 64 bytes minimal ethernet frame length.
  	 */
  	len += sizeof(struct ncsi_cmd_pkt_hdr) + 4;
  	if (nca->payload < 26)
  		len += 26;
  	else
  		len += nca->payload;
  
  	/* Allocate skb */
  	skb = alloc_skb(len, GFP_ATOMIC);
  	if (!skb) {
  		ncsi_free_request(nr);
  		return NULL;
  	}
  
  	nr->cmd = skb;
  	skb_reserve(skb, hlen);
  	skb_reset_network_header(skb);
  
  	skb->dev = dev;
  	skb->protocol = htons(ETH_P_NCSI);
  
  	return nr;
  }
  
  int ncsi_xmit_cmd(struct ncsi_cmd_arg *nca)
  {
  	struct ncsi_request *nr;
  	struct ethhdr *eh;
  	struct ncsi_cmd_handler *nch = NULL;
  	int i, ret;
  
  	/* Search for the handler */
  	for (i = 0; i < ARRAY_SIZE(ncsi_cmd_handlers); i++) {
  		if (ncsi_cmd_handlers[i].type == nca->type) {
  			if (ncsi_cmd_handlers[i].handler)
  				nch = &ncsi_cmd_handlers[i];
  			else
  				nch = NULL;
  
  			break;
  		}
  	}
  
  	if (!nch) {
  		netdev_err(nca->ndp->ndev.dev,
  			   "Cannot send packet with type 0x%02x
  ", nca->type);
  		return -ENOENT;
  	}
  
  	/* Get packet payload length and allocate the request */
  	nca->payload = nch->payload;
  	nr = ncsi_alloc_command(nca);
  	if (!nr)
  		return -ENOMEM;
  
  	/* Prepare the packet */
  	nca->id = nr->id;
  	ret = nch->handler(nr->cmd, nca);
  	if (ret) {
  		ncsi_free_request(nr);
  		return ret;
  	}
  
  	/* Fill the ethernet header */

  	eh = skb_push(nr->cmd, sizeof(*eh));

  	eh->h_proto = htons(ETH_P_NCSI);
  	eth_broadcast_addr(eh->h_dest);
  	eth_broadcast_addr(eh->h_source);
  
  	/* Start the timer for the request that might not have
  	 * corresponding response. Given NCSI is an internal
  	 * connection a 1 second delay should be sufficient.
  	 */
  	nr->enabled = true;
  	mod_timer(&nr->timer, jiffies + 1 * HZ);
  
  	/* Send NCSI packet */
  	skb_get(nr->cmd);
  	ret = dev_queue_xmit(nr->cmd);
  	if (ret < 0) {
  		ncsi_free_request(nr);
  		return ret;
  	}
  
  	return 0;
  }