/*
   * Copyright (C) ST-Ericsson AB 2010

   * Author:	Sjur Brendeland

   * License terms: GNU General Public License (GPL) version 2
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__

  #include <linux/stddef.h>
  #include <linux/spinlock.h>
  #include <linux/slab.h>
  #include <net/caif/caif_layer.h>
  #include <net/caif/cfpkt.h>
  #include <net/caif/cfserl.h>
  
  #define container_obj(layr) ((struct cfserl *) layr)
  
  #define CFSERL_STX 0x02

  #define SERIAL_MINIUM_PACKET_SIZE 4
  #define SERIAL_MAX_FRAMESIZE 4096

  struct cfserl {
  	struct cflayer layer;
  	struct cfpkt *incomplete_frm;
  	/* Protects parallel processing of incoming packets */
  	spinlock_t sync;
  	bool usestx;
  };

  
  static int cfserl_receive(struct cflayer *layr, struct cfpkt *pkt);
  static int cfserl_transmit(struct cflayer *layr, struct cfpkt *pkt);
  static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,

  			   int phyid);

  struct cflayer *cfserl_create(int instance, bool use_stx)

  {

  	struct cfserl *this = kzalloc(sizeof(struct cfserl), GFP_ATOMIC);
  	if (!this)

  		return NULL;

  	caif_assert(offsetof(struct cfserl, layer) == 0);

  	this->layer.receive = cfserl_receive;
  	this->layer.transmit = cfserl_transmit;
  	this->layer.ctrlcmd = cfserl_ctrlcmd;

  	this->usestx = use_stx;
  	spin_lock_init(&this->sync);
  	snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "ser1");
  	return &this->layer;
  }
  
  static int cfserl_receive(struct cflayer *l, struct cfpkt *newpkt)
  {
  	struct cfserl *layr = container_obj(l);
  	u16 pkt_len;
  	struct cfpkt *pkt = NULL;
  	struct cfpkt *tail_pkt = NULL;
  	u8 tmp8;
  	u16 tmp;
  	u8 stx = CFSERL_STX;
  	int ret;
  	u16 expectlen = 0;

  	caif_assert(newpkt != NULL);
  	spin_lock(&layr->sync);
  
  	if (layr->incomplete_frm != NULL) {

  		layr->incomplete_frm =
  		    cfpkt_append(layr->incomplete_frm, newpkt, expectlen);
  		pkt = layr->incomplete_frm;

  		if (pkt == NULL) {
  			spin_unlock(&layr->sync);

  			return -ENOMEM;

  		}

  	} else {
  		pkt = newpkt;
  	}
  	layr->incomplete_frm = NULL;
  
  	do {
  		/* Search for STX at start of pkt if STX is used */
  		if (layr->usestx) {
  			cfpkt_extr_head(pkt, &tmp8, 1);
  			if (tmp8 != CFSERL_STX) {
  				while (cfpkt_more(pkt)
  				       && tmp8 != CFSERL_STX) {
  					cfpkt_extr_head(pkt, &tmp8, 1);
  				}
  				if (!cfpkt_more(pkt)) {
  					cfpkt_destroy(pkt);
  					layr->incomplete_frm = NULL;
  					spin_unlock(&layr->sync);
  					return -EPROTO;
  				}
  			}
  		}
  
  		pkt_len = cfpkt_getlen(pkt);
  
  		/*
  		 *  pkt_len is the accumulated length of the packet data
  		 *  we have received so far.
  		 *  Exit if frame doesn't hold length.
  		 */
  
  		if (pkt_len < 2) {
  			if (layr->usestx)
  				cfpkt_add_head(pkt, &stx, 1);
  			layr->incomplete_frm = pkt;
  			spin_unlock(&layr->sync);
  			return 0;
  		}
  
  		/*
  		 *  Find length of frame.
  		 *  expectlen is the length we need for a full frame.
  		 */
  		cfpkt_peek_head(pkt, &tmp, 2);
  		expectlen = le16_to_cpu(tmp) + 2;
  		/*
  		 * Frame error handling
  		 */

  		if (expectlen < SERIAL_MINIUM_PACKET_SIZE
  		    || expectlen > SERIAL_MAX_FRAMESIZE) {

  			if (!layr->usestx) {
  				if (pkt != NULL)
  					cfpkt_destroy(pkt);
  				layr->incomplete_frm = NULL;
  				expectlen = 0;
  				spin_unlock(&layr->sync);
  				return -EPROTO;
  			}
  			continue;
  		}
  
  		if (pkt_len < expectlen) {
  			/* Too little received data */
  			if (layr->usestx)
  				cfpkt_add_head(pkt, &stx, 1);
  			layr->incomplete_frm = pkt;
  			spin_unlock(&layr->sync);
  			return 0;
  		}
  
  		/*
  		 * Enough data for at least one frame.
  		 * Split the frame, if too long
  		 */
  		if (pkt_len > expectlen)
  			tail_pkt = cfpkt_split(pkt, expectlen);
  		else
  			tail_pkt = NULL;
  
  		/* Send the first part of packet upwards.*/
  		spin_unlock(&layr->sync);
  		ret = layr->layer.up->receive(layr->layer.up, pkt);
  		spin_lock(&layr->sync);
  		if (ret == -EILSEQ) {
  			if (layr->usestx) {
  				if (tail_pkt != NULL)
  					pkt = cfpkt_append(pkt, tail_pkt, 0);

  				/* Start search for next STX if frame failed */
  				continue;
  			} else {
  				cfpkt_destroy(pkt);
  				pkt = NULL;
  			}
  		}
  
  		pkt = tail_pkt;
  
  	} while (pkt != NULL);
  
  	spin_unlock(&layr->sync);
  	return 0;
  }
  
  static int cfserl_transmit(struct cflayer *layer, struct cfpkt *newpkt)
  {
  	struct cfserl *layr = container_obj(layer);

  	u8 tmp8 = CFSERL_STX;
  	if (layr->usestx)
  		cfpkt_add_head(newpkt, &tmp8, 1);

  	return layer->dn->transmit(layer->dn, newpkt);

  }
  
  static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,

  			   int phyid)

  {
  	layr->up->ctrlcmd(layr->up, ctrl, phyid);
  }