text: /*
   * Copyright (C) ST-Ericsson AB 2010
   * Author:	Sjur Brendeland
   * License terms: GNU General Public License (GPL) version 2
   */
  
  #include <linux/hardirq.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/device.h>
  #include <linux/types.h>
  #include <linux/skbuff.h>
  #include <linux/netdevice.h>
  #include <linux/rtnetlink.h>
  #include <linux/tty.h>
  #include <linux/file.h>
  #include <linux/if_arp.h>
  #include <net/caif/caif_device.h>
  #include <net/caif/cfcnfg.h>
  #include <linux/err.h>
  #include <linux/debugfs.h>
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Sjur Brendeland");
  MODULE_DESCRIPTION("CAIF serial device TTY line discipline");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_LDISC(N_CAIF);
  
  #define SEND_QUEUE_LOW 10
  #define SEND_QUEUE_HIGH 100
  #define CAIF_SENDING	        1 /* Bit 1 = 0x02*/
  #define CAIF_FLOW_OFF_SENT	4 /* Bit 4 = 0x10 */
  #define MAX_WRITE_CHUNK	     4096
  #define ON 1
  #define OFF 0
  #define CAIF_MAX_MTU 4096
  
  static DEFINE_SPINLOCK(ser_lock);
  static LIST_HEAD(ser_list);
  static LIST_HEAD(ser_release_list);
  
  static bool ser_loop;
  module_param(ser_loop, bool, 0444);
  MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
  
  static bool ser_use_stx = true;
  module_param(ser_use_stx, bool, 0444);
  MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
  
  static bool ser_use_fcs = true;
  
  module_param(ser_use_fcs, bool, 0444);
  MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not.");
  
  static int ser_write_chunk = MAX_WRITE_CHUNK;
  module_param(ser_write_chunk, int, 0444);
  
  MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART.");
  
  static struct dentry *debugfsdir;
  
  static int caif_net_open(struct net_device *dev);
  static int caif_net_close(struct net_device *dev);
  
  struct ser_device {
  	struct caif_dev_common common;
  	struct list_head node;
  	struct net_device *dev;
  	struct sk_buff_head head;
  	struct tty_struct *tty;
  	bool tx_started;
  	unsigned long state;
  #ifdef CONFIG_DEBUG_FS
  	struct dentry *debugfs_tty_dir;
  	struct debugfs_blob_wrapper tx_blob;
  	struct debugfs_blob_wrapper rx_blob;
  	u8 rx_data[128];
  	u8 tx_data[128];
  	u8 tty_status;
  
  #endif
  };
  
  static void caifdev_setup(struct net_device *dev);
  static void ldisc_tx_wakeup(struct tty_struct *tty);
  #ifdef CONFIG_DEBUG_FS
  static inline void update_tty_status(struct ser_device *ser)
  {
  	ser->tty_status =
  		ser->tty->stopped << 5 |
  		ser->tty->flow_stopped << 3 |
  		ser->tty->packet << 2 |
  		ser->tty->port->low_latency << 1;
  }
  static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
  {
  	ser->debugfs_tty_dir =
  			debugfs_create_dir(tty->name, debugfsdir);
  	if (!IS_ERR(ser->debugfs_tty_dir)) {
  		debugfs_create_blob("last_tx_msg", 0400,
  				    ser->debugfs_tty_dir,
  				    &ser->tx_blob);
  
  		debugfs_create_blob("last_rx_msg", 0400,
  				    ser->debugfs_tty_dir,
  				    &ser->rx_blob);
  
  		debugfs_create_x32("ser_state", 0400,
  				   ser->debugfs_tty_dir,
  				   (u32 *)&ser->state);
  
  		debugfs_create_x8("tty_status", 0400,
  				  ser->debugfs_tty_dir,
  				  &ser->tty_status);
  
  	}
  	ser->tx_blob.data = ser->tx_data;
  	ser->tx_blob.size = 0;
  	ser->rx_blob.data = ser->rx_data;
  	ser->rx_blob.size = 0;
  }
  
  static inline void debugfs_deinit(struct ser_device *ser)
  {
  	debugfs_remove_recursive(ser->debugfs_tty_dir);
  }
  
  static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
  {
  	if (size > sizeof(ser->rx_data))
  		size = sizeof(ser->rx_data);
  	memcpy(ser->rx_data, data, size);
  	ser->rx_blob.data = ser->rx_data;
  	ser->rx_blob.size = size;
  }
  
  static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
  {
  	if (size > sizeof(ser->tx_data))
  		size = sizeof(ser->tx_data);
  	memcpy(ser->tx_data, data, size);
  	ser->tx_blob.data = ser->tx_data;
  	ser->tx_blob.size = size;
  }
  #else
  static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
  {
  }
  
  static inline void debugfs_deinit(struct ser_device *ser)
  {
  }
  
  static inline void update_tty_status(struct ser_device *ser)
  {
  }
  
  static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
  {
  }
  
  static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
  {
  }
  
  #endif
  
  static void ldisc_receive(struct tty_struct *tty, const u8 *data,
  			char *flags, int count)
  {
  	struct sk_buff *skb = NULL;
  	struct ser_device *ser;
  	int ret;
  
  	ser = tty->disc_data;
  
  	/*
  	 * NOTE: flags may contain information about break or overrun.
  	 * This is not yet handled.
  	 */
  
  
  	/*
  	 * Workaround for garbage at start of transmission,
  	 * only enable if STX handling is not enabled.
  	 */
  	if (!ser->common.use_stx && !ser->tx_started) {
  		dev_info(&ser->dev->dev,
  			"Bytes received before initial transmission -"
  			"bytes discarded.\n");
  		return;
  	}
  
  	BUG_ON(ser->dev == NULL);
  
  	/* Get a suitable caif packet and copy in data. */
  	skb = netdev_alloc_skb(ser->dev, count+1);
  	if (skb == NULL)
  		return;
  	skb_put_data(skb, data, count);
  
  	skb->protocol = htons(ETH_P_CAIF);
  	skb_reset_mac_header(skb);
  	debugfs_rx(ser, data, count);
  	/* Push received packet up the stack. */
  	ret = netif_rx_ni(skb);
  	if (!ret) {
  		ser->dev->stats.rx_packets++;
  		ser->dev->stats.rx_bytes += count;
  	} else
  		++ser->dev->stats.rx_dropped;
  	update_tty_status(ser);
  }
  
  static int handle_tx(struct ser_device *ser)
  {
  	struct tty_struct *tty;
  	struct sk_buff *skb;
  	int tty_wr, len, room;
  
  	tty = ser->tty;
  	ser->tx_started = true;
  
  	/* Enter critical section */
  	if (test_and_set_bit(CAIF_SENDING, &ser->state))
  		return 0;
  
  	/* skb_peek is safe because handle_tx is called after skb_queue_tail */
  	while ((skb = skb_peek(&ser->head)) != NULL) {
  
  		/* Make sure you don't write too much */
  		len = skb->len;
  		room = tty_write_room(tty);
  		if (!room)
  			break;
  		if (room > ser_write_chunk)
  			room = ser_write_chunk;
  		if (len > room)
  			len = room;
  
  		/* Write to tty or loopback */
  		if (!ser_loop) {
  			tty_wr = tty->ops->write(tty, skb->data, len);
  			update_tty_status(ser);
  		} else {
  			tty_wr = len;
  			ldisc_receive(tty, skb->data, NULL, len);
  		}
  		ser->dev->stats.tx_packets++;
  		ser->dev->stats.tx_bytes += tty_wr;
  
  		/* Error on TTY ?! */
  		if (tty_wr < 0)
  			goto error;
  		/* Reduce buffer written, and discard if empty */
  		skb_pull(skb, tty_wr);
  		if (skb->len == 0) {
  			struct sk_buff *tmp = skb_dequeue(&ser->head);
  			WARN_ON(tmp != skb);
  			dev_consume_skb_any(skb);
  		}
  	}
  	/* Send flow off if queue is empty */
  	if (ser->head.qlen <= SEND_QUEUE_LOW &&
  		test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
  		ser->common.flowctrl != NULL)
  				ser->common.flowctrl(ser->dev, ON);
  	clear_bit(CAIF_SENDING, &ser->state);
  	return 0;
  error:
  	clear_bit(CAIF_SENDING, &ser->state);
  	return tty_wr;
  }
  
  static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
  {
  	struct ser_device *ser;
  
  	BUG_ON(dev == NULL);
  	ser = netdev_priv(dev);
  
  	/* Send flow off once, on high water mark */
  	if (ser->head.qlen > SEND_QUEUE_HIGH &&
  		!test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
  		ser->common.flowctrl != NULL)
  
  		ser->common.flowctrl(ser->dev, OFF);
  
  	skb_queue_tail(&ser->head, skb);
  	return handle_tx(ser);
  }
  
  
  static void ldisc_tx_wakeup(struct tty_struct *tty)
  {
  	struct ser_device *ser;
  
  	ser = tty->disc_data;
  	BUG_ON(ser == NULL);
  	WARN_ON(ser->tty != tty);
  	handle_tx(ser);
  }
  
  
  static void ser_release(struct work_struct *work)
  {
  	struct list_head list;
  	struct ser_device *ser, *tmp;
  
  	spin_lock(&ser_lock);
  	list_replace_init(&ser_release_list, &list);
  	spin_unlock(&ser_lock);
  
  	if (!list_empty(&list)) {
  		rtnl_lock();
  		list_for_each_entry_safe(ser, tmp, &list, node) {
  			dev_close(ser->dev);
  			unregister_netdevice(ser->dev);
  			debugfs_deinit(ser);
  		}
  		rtnl_unlock();
  	}
  }
  
  static DECLARE_WORK(ser_release_work, ser_release);
  
  static int ldisc_open(struct tty_struct *tty)
  {
  	struct ser_device *ser;
  	struct net_device *dev;
  	char name[64];
  	int result;
  
  	/* No write no play */
  	if (tty->ops->write == NULL)
  		return -EOPNOTSUPP;
  	if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
  		return -EPERM;
  
  	/* release devices to avoid name collision */
  	ser_release(NULL);
  
  	result = snprintf(name, sizeof(name), "cf%s", tty->name);
  	if (result >= IFNAMSIZ)
  		return -EINVAL;
  	dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
  			   caifdev_setup);
  	if (!dev)
  		return -ENOMEM;
  
  	ser = netdev_priv(dev);
  	ser->tty = tty_kref_get(tty);
  	ser->dev = dev;
  	debugfs_init(ser, tty);
  	tty->receive_room = N_TTY_BUF_SIZE;
  	tty->disc_data = ser;
  	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
  	rtnl_lock();
  	result = register_netdevice(dev);
  	if (result) {
  		rtnl_unlock();
  		free_netdev(dev);
  		return -ENODEV;
  	}
  
  	spin_lock(&ser_lock);
  	list_add(&ser->node, &ser_list);
  	spin_unlock(&ser_lock);
  	rtnl_unlock();
  	netif_stop_queue(dev);
  	update_tty_status(ser);
  	return 0;
  }
  
  static void ldisc_close(struct tty_struct *tty)
  {
  	struct ser_device *ser = tty->disc_data;
  
  	tty_kref_put(ser->tty);
  
  	spin_lock(&ser_lock);
  	list_move(&ser->node, &ser_release_list);
  	spin_unlock(&ser_lock);
  	schedule_work(&ser_release_work);
  }
  
  /* The line discipline structure. */
  static struct tty_ldisc_ops caif_ldisc = {
  	.owner =	THIS_MODULE,
  	.magic =	TTY_LDISC_MAGIC,
  	.name =		"n_caif",
  	.open =		ldisc_open,
  	.close =	ldisc_close,
  	.receive_buf =	ldisc_receive,
  	.write_wakeup =	ldisc_tx_wakeup
  };
  
  static int register_ldisc(void)
  {
  	int result;
  
  	result = tty_register_ldisc(N_CAIF, &caif_ldisc);
  	if (result < 0) {
  		pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
  			result);
  		return result;
  	}
  	return result;
  }
  static const struct net_device_ops netdev_ops = {
  	.ndo_open = caif_net_open,
  	.ndo_stop = caif_net_close,
  	.ndo_start_xmit = caif_xmit
  };
  
  static void caifdev_setup(struct net_device *dev)
  {
  	struct ser_device *serdev = netdev_priv(dev);
  
  	dev->features = 0;
  	dev->netdev_ops = &netdev_ops;
  	dev->type = ARPHRD_CAIF;
  	dev->flags = IFF_POINTOPOINT | IFF_NOARP;
  	dev->mtu = CAIF_MAX_MTU;
  	dev->priv_flags |= IFF_NO_QUEUE;
  	dev->needs_free_netdev = true;
  	skb_queue_head_init(&serdev->head);
  	serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
  	serdev->common.use_frag = true;
  	serdev->common.use_stx = ser_use_stx;
  	serdev->common.use_fcs = ser_use_fcs;
  	serdev->dev = dev;
  }
  
  
  static int caif_net_open(struct net_device *dev)
  {
  	netif_wake_queue(dev);
  	return 0;
  }
  
  static int caif_net_close(struct net_device *dev)
  {
  	netif_stop_queue(dev);
  	return 0;
  }
  
  static int __init caif_ser_init(void)
  {
  	int ret;
  
  	ret = register_ldisc();
  	debugfsdir = debugfs_create_dir("caif_serial", NULL);
  	return ret;
  }
  
  static void __exit caif_ser_exit(void)
  {
  	spin_lock(&ser_lock);
  	list_splice(&ser_list, &ser_release_list);
  	spin_unlock(&ser_lock);
  	ser_release(NULL);
  	cancel_work_sync(&ser_release_work);
  	tty_unregister_ldisc(N_CAIF);
  	debugfs_remove_recursive(debugfsdir);
  }
  
  module_init(caif_ser_init);
  module_exit(caif_ser_exit);
  