/*
   * CAIF Framing Layer.
   *
   * Copyright (C) ST-Ericsson AB 2010
   * Author:	Sjur Brendeland/sjur.brandeland@stericsson.com
   * 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 <linux/crc-ccitt.h>

  #include <linux/netdevice.h>

  #include <net/caif/caif_layer.h>
  #include <net/caif/cfpkt.h>
  #include <net/caif/cffrml.h>
  
  #define container_obj(layr) container_of(layr, struct cffrml, layer)
  
  struct cffrml {
  	struct cflayer layer;
  	bool dofcs;		/* !< FCS active */

  	int __percpu		*pcpu_refcnt;

  };
  
  static int cffrml_receive(struct cflayer *layr, struct cfpkt *pkt);
  static int cffrml_transmit(struct cflayer *layr, struct cfpkt *pkt);
  static void cffrml_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
  				int phyid);
  
  static u32 cffrml_rcv_error;
  static u32 cffrml_rcv_checsum_error;
  struct cflayer *cffrml_create(u16 phyid, bool use_fcs)
  {

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

  		return NULL;

  	this->pcpu_refcnt = alloc_percpu(int);
  	if (this->pcpu_refcnt == NULL) {
  		kfree(this);
  		return NULL;
  	}

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

  	this->layer.receive = cffrml_receive;
  	this->layer.transmit = cffrml_transmit;
  	this->layer.ctrlcmd = cffrml_ctrlcmd;
  	snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "frm%d", phyid);
  	this->dofcs = use_fcs;
  	this->layer.id = phyid;
  	return (struct cflayer *) this;
  }

  void cffrml_free(struct cflayer *layer)
  {
  	struct cffrml *this = container_obj(layer);
  	free_percpu(this->pcpu_refcnt);
  	kfree(layer);
  }

  void cffrml_set_uplayer(struct cflayer *this, struct cflayer *up)
  {
  	this->up = up;
  }
  
  void cffrml_set_dnlayer(struct cflayer *this, struct cflayer *dn)
  {
  	this->dn = dn;
  }
  
  static u16 cffrml_checksum(u16 chks, void *buf, u16 len)
  {
  	/* FIXME: FCS should be moved to glue in order to use OS-Specific
  	 * solutions
  	 */
  	return crc_ccitt(chks, buf, len);
  }
  
  static int cffrml_receive(struct cflayer *layr, struct cfpkt *pkt)
  {
  	u16 tmp;
  	u16 len;
  	u16 hdrchks;
  	u16 pktchks;
  	struct cffrml *this;
  	this = container_obj(layr);
  
  	cfpkt_extr_head(pkt, &tmp, 2);
  	len = le16_to_cpu(tmp);
  
  	/* Subtract for FCS on length if FCS is not used. */
  	if (!this->dofcs)
  		len -= 2;
  
  	if (cfpkt_setlen(pkt, len) < 0) {
  		++cffrml_rcv_error;

  		pr_err("Framing length error (%d)
  ", len);

  		cfpkt_destroy(pkt);
  		return -EPROTO;
  	}
  	/*
  	 * Don't do extract if FCS is false, rather do setlen - then we don't
  	 * get a cache-miss.
  	 */
  	if (this->dofcs) {
  		cfpkt_extr_trail(pkt, &tmp, 2);
  		hdrchks = le16_to_cpu(tmp);
  		pktchks = cfpkt_iterate(pkt, cffrml_checksum, 0xffff);
  		if (pktchks != hdrchks) {
  			cfpkt_add_trail(pkt, &tmp, 2);
  			++cffrml_rcv_error;
  			++cffrml_rcv_checsum_error;

  			pr_info("Frame checksum error (0x%x != 0x%x)
  ",
  				hdrchks, pktchks);

  			return -EILSEQ;
  		}
  	}
  	if (cfpkt_erroneous(pkt)) {
  		++cffrml_rcv_error;

  		pr_err("Packet is erroneous!
  ");

  		cfpkt_destroy(pkt);
  		return -EPROTO;
  	}

  
  	if (layr->up == NULL) {
  		pr_err("Layr up is missing!
  ");
  		cfpkt_destroy(pkt);
  		return -EINVAL;
  	}

  	return layr->up->receive(layr->up, pkt);
  }
  
  static int cffrml_transmit(struct cflayer *layr, struct cfpkt *pkt)
  {

  	u16 chks;
  	u16 len;

  	__le16 data;

  	struct cffrml *this = container_obj(layr);
  	if (this->dofcs) {
  		chks = cfpkt_iterate(pkt, cffrml_checksum, 0xffff);

  		data = cpu_to_le16(chks);
  		cfpkt_add_trail(pkt, &data, 2);

  	} else {
  		cfpkt_pad_trail(pkt, 2);
  	}
  	len = cfpkt_getlen(pkt);

  	data = cpu_to_le16(len);
  	cfpkt_add_head(pkt, &data, 2);

  	cfpkt_info(pkt)->hdr_len += 2;
  	if (cfpkt_erroneous(pkt)) {

  		pr_err("Packet is erroneous!
  ");

  		cfpkt_destroy(pkt);

  		return -EPROTO;
  	}

  
  	if (layr->dn == NULL) {
  		cfpkt_destroy(pkt);
  		return -ENODEV;
  
  	}

  	return layr->dn->transmit(layr->dn, pkt);

  }
  
  static void cffrml_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
  					int phyid)
  {

  	if (layr->up && layr->up->ctrlcmd)

  		layr->up->ctrlcmd(layr->up, ctrl, layr->id);
  }

  
  void cffrml_put(struct cflayer *layr)
  {

  	struct cffrml *this = container_obj(layr);
  	if (layr != NULL && this->pcpu_refcnt != NULL)

  		this_cpu_dec(*this->pcpu_refcnt);

  }
  
  void cffrml_hold(struct cflayer *layr)
  {

  	struct cffrml *this = container_obj(layr);
  	if (layr != NULL && this->pcpu_refcnt != NULL)

  		this_cpu_inc(*this->pcpu_refcnt);

  }
  
  int cffrml_refcnt_read(struct cflayer *layr)
  {
  	int i, refcnt = 0;
  	struct cffrml *this = container_obj(layr);
  	for_each_possible_cpu(i)
  		refcnt += *per_cpu_ptr(this->pcpu_refcnt, i);
  	return refcnt;

  }