/*
   * Copyright (C) 2006, 2007, 2009 Rusty Russell, IBM Corporation

   * Copyright (C) 2009, 2010, 2011 Red Hat, Inc.
   * Copyright (C) 2009, 2010, 2011 Amit Shah <amit.shah@redhat.com>

   *
   * 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.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */

  #include <linux/cdev.h>

  #include <linux/debugfs.h>

  #include <linux/completion.h>

  #include <linux/device.h>

  #include <linux/err.h>

  #include <linux/freezer.h>

  #include <linux/fs.h>

  #include <linux/init.h>

  #include <linux/list.h>

  #include <linux/poll.h>
  #include <linux/sched.h>

  #include <linux/slab.h>

  #include <linux/spinlock.h>

  #include <linux/virtio.h>
  #include <linux/virtio_console.h>

  #include <linux/wait.h>

  #include <linux/workqueue.h>

  #include <linux/module.h>

  #include "../tty/hvc/hvc_console.h"

  /*
   * This is a global struct for storing common data for all the devices
   * this driver handles.
   *
   * Mainly, it has a linked list for all the consoles in one place so
   * that callbacks from hvc for get_chars(), put_chars() work properly
   * across multiple devices and multiple ports per device.
   */
  struct ports_driver_data {

  	/* Used for registering chardevs */
  	struct class *class;

  	/* Used for exporting per-port information to debugfs */
  	struct dentry *debugfs_dir;

  	/* List of all the devices we're handling */
  	struct list_head portdevs;

  	/* Number of devices this driver is handling */
  	unsigned int index;

  	/*
  	 * This is used to keep track of the number of hvc consoles
  	 * spawned by this driver.  This number is given as the first
  	 * argument to hvc_alloc().  To correctly map an initial
  	 * console spawned via hvc_instantiate to the console being
  	 * hooked up via hvc_alloc, we need to pass the same vtermno.
  	 *
  	 * We also just assume the first console being initialised was
  	 * the first one that got used as the initial console.
  	 */
  	unsigned int next_vtermno;

  	/* All the console devices handled by this driver */
  	struct list_head consoles;
  };
  static struct ports_driver_data pdrvdata;
  
  DEFINE_SPINLOCK(pdrvdata_lock);

  DECLARE_COMPLETION(early_console_added);

  /* This struct holds information that's relevant only for console ports */
  struct console {
  	/* We'll place all consoles in a list in the pdrvdata struct */
  	struct list_head list;
  
  	/* The hvc device associated with this console port */
  	struct hvc_struct *hvc;

  	/* The size of the console */
  	struct winsize ws;

  	/*
  	 * This number identifies the number that we used to register
  	 * with hvc in hvc_instantiate() and hvc_alloc(); this is the
  	 * number passed on by the hvc callbacks to us to
  	 * differentiate between the other console ports handled by
  	 * this driver
  	 */
  	u32 vtermno;
  };

  struct port_buffer {
  	char *buf;
  
  	/* size of the buffer in *buf above */
  	size_t size;
  
  	/* used length of the buffer */
  	size_t len;
  	/* offset in the buf from which to consume data */
  	size_t offset;
  };

  /*
   * This is a per-device struct that stores data common to all the
   * ports for that device (vdev->priv).
   */
  struct ports_device {

  	/* Next portdev in the list, head is in the pdrvdata struct */
  	struct list_head list;

  	/*
  	 * Workqueue handlers where we process deferred work after
  	 * notification
  	 */
  	struct work_struct control_work;
  
  	struct list_head ports;
  
  	/* To protect the list of ports */
  	spinlock_t ports_lock;
  
  	/* To protect the vq operations for the control channel */
  	spinlock_t cvq_lock;
  
  	/* The current config space is stored here */

  	struct virtio_console_config config;

  
  	/* The virtio device we're associated with */
  	struct virtio_device *vdev;
  
  	/*
  	 * A couple of virtqueues for the control channel: one for
  	 * guest->host transfers, one for host->guest transfers
  	 */
  	struct virtqueue *c_ivq, *c_ovq;
  
  	/* Array of per-port IO virtqueues */
  	struct virtqueue **in_vqs, **out_vqs;

  
  	/* Used for numbering devices for sysfs and debugfs */
  	unsigned int drv_index;
  
  	/* Major number for this device.  Ports will be created as minors. */
  	int chr_major;

  };

  struct port_stats {
  	unsigned long bytes_sent, bytes_received, bytes_discarded;
  };

  /* This struct holds the per-port data */

  struct port {

  	/* Next port in the list, head is in the ports_device */
  	struct list_head list;

  	/* Pointer to the parent virtio_console device */
  	struct ports_device *portdev;

  
  	/* The current buffer from which data has to be fed to readers */
  	struct port_buffer *inbuf;

  	/*
  	 * To protect the operations on the in_vq associated with this
  	 * port.  Has to be a spinlock because it can be called from
  	 * interrupt context (get_char()).
  	 */
  	spinlock_t inbuf_lock;

  	/* Protect the operations on the out_vq. */
  	spinlock_t outvq_lock;

  	/* The IO vqs for this port */
  	struct virtqueue *in_vq, *out_vq;

  	/* File in the debugfs directory that exposes this port's information */
  	struct dentry *debugfs_file;

  	/*

  	 * Keep count of the bytes sent, received and discarded for
  	 * this port for accounting and debugging purposes.  These
  	 * counts are not reset across port open / close events.
  	 */
  	struct port_stats stats;
  
  	/*

  	 * The entries in this struct will be valid if this port is
  	 * hooked up to an hvc console
  	 */
  	struct console cons;

  	/* Each port associates with a separate char device */

  	struct cdev *cdev;

  	struct device *dev;

  	/* Reference-counting to handle port hot-unplugs and file operations */
  	struct kref kref;

  	/* A waitqueue for poll() or blocking read operations */
  	wait_queue_head_t waitqueue;

  	/* The 'name' of the port that we expose via sysfs properties */
  	char *name;

  	/* We can notify apps of host connect / disconnect events via SIGIO */
  	struct fasync_struct *async_queue;

  	/* The 'id' to identify the port with the Host */
  	u32 id;

  	bool outvq_full;

  	/* Is the host device open */
  	bool host_connected;

  
  	/* We should allow only one process to open a port */
  	bool guest_connected;

  };

  /* This is the very early arch-specified put chars function. */
  static int (*early_put_chars)(u32, const char *, int);

  static struct port *find_port_by_vtermno(u32 vtermno)
  {
  	struct port *port;

  	struct console *cons;

  	unsigned long flags;
  
  	spin_lock_irqsave(&pdrvdata_lock, flags);

  	list_for_each_entry(cons, &pdrvdata.consoles, list) {
  		if (cons->vtermno == vtermno) {
  			port = container_of(cons, struct port, cons);

  			goto out;

  		}

  	}
  	port = NULL;
  out:
  	spin_unlock_irqrestore(&pdrvdata_lock, flags);
  	return port;
  }

  static struct port *find_port_by_devt_in_portdev(struct ports_device *portdev,
  						 dev_t dev)
  {
  	struct port *port;
  	unsigned long flags;
  
  	spin_lock_irqsave(&portdev->ports_lock, flags);
  	list_for_each_entry(port, &portdev->ports, list)

  		if (port->cdev->dev == dev)

  			goto out;
  	port = NULL;
  out:
  	spin_unlock_irqrestore(&portdev->ports_lock, flags);
  
  	return port;
  }
  
  static struct port *find_port_by_devt(dev_t dev)
  {
  	struct ports_device *portdev;
  	struct port *port;
  	unsigned long flags;
  
  	spin_lock_irqsave(&pdrvdata_lock, flags);
  	list_for_each_entry(portdev, &pdrvdata.portdevs, list) {
  		port = find_port_by_devt_in_portdev(portdev, dev);
  		if (port)
  			goto out;
  	}
  	port = NULL;
  out:
  	spin_unlock_irqrestore(&pdrvdata_lock, flags);
  	return port;
  }

  static struct port *find_port_by_id(struct ports_device *portdev, u32 id)
  {
  	struct port *port;
  	unsigned long flags;
  
  	spin_lock_irqsave(&portdev->ports_lock, flags);
  	list_for_each_entry(port, &portdev->ports, list)
  		if (port->id == id)
  			goto out;
  	port = NULL;
  out:
  	spin_unlock_irqrestore(&portdev->ports_lock, flags);
  
  	return port;
  }

  static struct port *find_port_by_vq(struct ports_device *portdev,
  				    struct virtqueue *vq)
  {
  	struct port *port;

  	unsigned long flags;

  	spin_lock_irqsave(&portdev->ports_lock, flags);
  	list_for_each_entry(port, &portdev->ports, list)

  		if (port->in_vq == vq || port->out_vq == vq)
  			goto out;

  	port = NULL;
  out:

  	spin_unlock_irqrestore(&portdev->ports_lock, flags);

  	return port;
  }

  static bool is_console_port(struct port *port)
  {
  	if (port->cons.hvc)
  		return true;
  	return false;
  }
  
  static inline bool use_multiport(struct ports_device *portdev)
  {
  	/*
  	 * This condition can be true when put_chars is called from
  	 * early_init
  	 */
  	if (!portdev->vdev)
  		return 0;
  	return portdev->vdev->features[0] & (1 << VIRTIO_CONSOLE_F_MULTIPORT);
  }

  static void free_buf(struct port_buffer *buf)
  {
  	kfree(buf->buf);
  	kfree(buf);
  }
  
  static struct port_buffer *alloc_buf(size_t buf_size)
  {
  	struct port_buffer *buf;
  
  	buf = kmalloc(sizeof(*buf), GFP_KERNEL);
  	if (!buf)
  		goto fail;
  	buf->buf = kzalloc(buf_size, GFP_KERNEL);
  	if (!buf->buf)
  		goto free_buf;
  	buf->len = 0;
  	buf->offset = 0;
  	buf->size = buf_size;
  	return buf;
  
  free_buf:
  	kfree(buf);
  fail:
  	return NULL;
  }

  /* Callers should take appropriate locks */

  static struct port_buffer *get_inbuf(struct port *port)

  {
  	struct port_buffer *buf;

  	unsigned int len;

  	if (port->inbuf)
  		return port->inbuf;
  
  	buf = virtqueue_get_buf(port->in_vq, &len);

  	if (buf) {
  		buf->len = len;
  		buf->offset = 0;

  		port->stats.bytes_received += len;

  	}
  	return buf;
  }

  /*

   * Create a scatter-gather list representing our input buffer and put
   * it in the queue.
   *
   * Callers should take appropriate locks.
   */

  static int add_inbuf(struct virtqueue *vq, struct port_buffer *buf)

  {
  	struct scatterlist sg[1];

  	int ret;

  	sg_init_one(sg, buf->buf, buf->size);

  	ret = virtqueue_add_buf(vq, sg, 0, 1, buf, GFP_ATOMIC);

  	virtqueue_kick(vq);

  	return ret;
  }

  /* Discard any unread data this port has. Callers lockers. */
  static void discard_port_data(struct port *port)
  {
  	struct port_buffer *buf;

  	unsigned int err;

  	if (!port->portdev) {
  		/* Device has been unplugged.  vqs are already gone. */
  		return;
  	}

  	buf = get_inbuf(port);

  	err = 0;

  	while (buf) {

  		port->stats.bytes_discarded += buf->len - buf->offset;

  		if (add_inbuf(port->in_vq, buf) < 0) {

  			err++;

  			free_buf(buf);
  		}

  		port->inbuf = NULL;
  		buf = get_inbuf(port);

  	}

  	if (err)

  		dev_warn(port->dev, "Errors adding %d buffers back to vq
  ",

  			 err);

  }

  static bool port_has_data(struct port *port)
  {
  	unsigned long flags;
  	bool ret;

  	ret = false;

  	spin_lock_irqsave(&port->inbuf_lock, flags);

  	port->inbuf = get_inbuf(port);

  	if (port->inbuf)

  		ret = true;

  	spin_unlock_irqrestore(&port->inbuf_lock, flags);

  	return ret;
  }

  static ssize_t __send_control_msg(struct ports_device *portdev, u32 port_id,
  				  unsigned int event, unsigned int value)

  {
  	struct scatterlist sg[1];
  	struct virtio_console_control cpkt;
  	struct virtqueue *vq;

  	unsigned int len;

  	if (!use_multiport(portdev))

  		return 0;

  	cpkt.id = port_id;

  	cpkt.event = event;
  	cpkt.value = value;

  	vq = portdev->c_ovq;

  
  	sg_init_one(sg, &cpkt, sizeof(cpkt));

  	if (virtqueue_add_buf(vq, sg, 1, 0, &cpkt, GFP_ATOMIC) >= 0) {

  		virtqueue_kick(vq);
  		while (!virtqueue_get_buf(vq, &len))

  			cpu_relax();
  	}
  	return 0;
  }

  static ssize_t send_control_msg(struct port *port, unsigned int event,
  				unsigned int value)
  {

  	/* Did the port get unplugged before userspace closed it? */
  	if (port->portdev)
  		return __send_control_msg(port->portdev, port->id, event, value);
  	return 0;

  }

  /* Callers must take the port->outvq_lock */
  static void reclaim_consumed_buffers(struct port *port)
  {
  	void *buf;
  	unsigned int len;

  	if (!port->portdev) {
  		/* Device has been unplugged.  vqs are already gone. */
  		return;
  	}

  	while ((buf = virtqueue_get_buf(port->out_vq, &len))) {
  		kfree(buf);
  		port->outvq_full = false;
  	}
  }
  
  static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count,
  			bool nonblock)

  {
  	struct scatterlist sg[1];
  	struct virtqueue *out_vq;
  	ssize_t ret;

  	unsigned long flags;

  	unsigned int len;
  
  	out_vq = port->out_vq;

  	spin_lock_irqsave(&port->outvq_lock, flags);
  
  	reclaim_consumed_buffers(port);

  	sg_init_one(sg, in_buf, in_count);

  	ret = virtqueue_add_buf(out_vq, sg, 1, 0, in_buf, GFP_ATOMIC);

  
  	/* Tell Host to go! */

  	virtqueue_kick(out_vq);

  
  	if (ret < 0) {

  		in_count = 0;

  		goto done;

  	}

  	if (ret == 0)
  		port->outvq_full = true;
  
  	if (nonblock)
  		goto done;
  
  	/*
  	 * Wait till the host acknowledges it pushed out the data we

  	 * sent.  This is done for data from the hvc_console; the tty
  	 * operations are performed with spinlocks held so we can't
  	 * sleep here.  An alternative would be to copy the data to a
  	 * buffer and relax the spinning requirement.  The downside is
  	 * we need to kmalloc a GFP_ATOMIC buffer each time the
  	 * console driver writes something out.

  	 */

  	while (!virtqueue_get_buf(out_vq, &len))

  		cpu_relax();

  done:
  	spin_unlock_irqrestore(&port->outvq_lock, flags);

  
  	port->stats.bytes_sent += in_count;

  	/*
  	 * We're expected to return the amount of data we wrote -- all
  	 * of it
  	 */

  	return in_count;

  }

  /*
   * Give out the data that's requested from the buffer that we have
   * queued up.
   */

  static ssize_t fill_readbuf(struct port *port, char *out_buf, size_t out_count,
  			    bool to_user)

  {
  	struct port_buffer *buf;
  	unsigned long flags;
  
  	if (!out_count || !port_has_data(port))
  		return 0;
  
  	buf = port->inbuf;

  	out_count = min(out_count, buf->len - buf->offset);

  	if (to_user) {
  		ssize_t ret;
  
  		ret = copy_to_user(out_buf, buf->buf + buf->offset, out_count);
  		if (ret)
  			return -EFAULT;
  	} else {
  		memcpy(out_buf, buf->buf + buf->offset, out_count);
  	}

  	buf->offset += out_count;
  
  	if (buf->offset == buf->len) {
  		/*
  		 * We're done using all the data in this buffer.
  		 * Re-queue so that the Host can send us more data.
  		 */
  		spin_lock_irqsave(&port->inbuf_lock, flags);
  		port->inbuf = NULL;
  
  		if (add_inbuf(port->in_vq, buf) < 0)

  			dev_warn(port->dev, "failed add_buf
  ");

  
  		spin_unlock_irqrestore(&port->inbuf_lock, flags);
  	}

  	/* Return the number of bytes actually copied */

  	return out_count;

  }

  /* The condition that must be true for polling to end */

  static bool will_read_block(struct port *port)

  {

  	if (!port->guest_connected) {
  		/* Port got hot-unplugged. Let's exit. */
  		return false;
  	}

  	return !port_has_data(port) && port->host_connected;

  }

  static bool will_write_block(struct port *port)
  {
  	bool ret;

  	if (!port->guest_connected) {
  		/* Port got hot-unplugged. Let's exit. */
  		return false;
  	}

  	if (!port->host_connected)
  		return true;
  
  	spin_lock_irq(&port->outvq_lock);
  	/*
  	 * Check if the Host has consumed any buffers since we last
  	 * sent data (this is only applicable for nonblocking ports).
  	 */
  	reclaim_consumed_buffers(port);
  	ret = port->outvq_full;
  	spin_unlock_irq(&port->outvq_lock);
  
  	return ret;
  }

  static ssize_t port_fops_read(struct file *filp, char __user *ubuf,
  			      size_t count, loff_t *offp)
  {
  	struct port *port;
  	ssize_t ret;
  
  	port = filp->private_data;
  
  	if (!port_has_data(port)) {
  		/*
  		 * If nothing's connected on the host just return 0 in
  		 * case of list_empty; this tells the userspace app
  		 * that there's no connection
  		 */
  		if (!port->host_connected)
  			return 0;
  		if (filp->f_flags & O_NONBLOCK)
  			return -EAGAIN;

  		ret = wait_event_freezable(port->waitqueue,
  					   !will_read_block(port));

  		if (ret < 0)
  			return ret;
  	}

  	/* Port got hot-unplugged. */
  	if (!port->guest_connected)
  		return -ENODEV;

  	/*
  	 * We could've received a disconnection message while we were
  	 * waiting for more data.
  	 *
  	 * This check is not clubbed in the if() statement above as we
  	 * might receive some data as well as the host could get
  	 * disconnected after we got woken up from our wait.  So we
  	 * really want to give off whatever data we have and only then
  	 * check for host_connected.
  	 */
  	if (!port_has_data(port) && !port->host_connected)
  		return 0;
  
  	return fill_readbuf(port, ubuf, count, true);
  }
  
  static ssize_t port_fops_write(struct file *filp, const char __user *ubuf,
  			       size_t count, loff_t *offp)
  {
  	struct port *port;
  	char *buf;
  	ssize_t ret;

  	bool nonblock;

  	/* Userspace could be out to fool us */
  	if (!count)
  		return 0;

  	port = filp->private_data;

  	nonblock = filp->f_flags & O_NONBLOCK;
  
  	if (will_write_block(port)) {
  		if (nonblock)
  			return -EAGAIN;

  		ret = wait_event_freezable(port->waitqueue,
  					   !will_write_block(port));

  		if (ret < 0)
  			return ret;
  	}

  	/* Port got hot-unplugged. */
  	if (!port->guest_connected)
  		return -ENODEV;

  	count = min((size_t)(32 * 1024), count);
  
  	buf = kmalloc(count, GFP_KERNEL);
  	if (!buf)
  		return -ENOMEM;
  
  	ret = copy_from_user(buf, ubuf, count);
  	if (ret) {
  		ret = -EFAULT;
  		goto free_buf;
  	}

  	/*
  	 * We now ask send_buf() to not spin for generic ports -- we
  	 * can re-use the same code path that non-blocking file
  	 * descriptors take for blocking file descriptors since the
  	 * wait is already done and we're certain the write will go
  	 * through to the host.
  	 */
  	nonblock = true;

  	ret = send_buf(port, buf, count, nonblock);
  
  	if (nonblock && ret > 0)
  		goto out;

  free_buf:
  	kfree(buf);

  out:

  	return ret;
  }
  
  static unsigned int port_fops_poll(struct file *filp, poll_table *wait)
  {
  	struct port *port;
  	unsigned int ret;
  
  	port = filp->private_data;
  	poll_wait(filp, &port->waitqueue, wait);

  	if (!port->guest_connected) {
  		/* Port got unplugged */
  		return POLLHUP;
  	}

  	ret = 0;

  	if (!will_read_block(port))

  		ret |= POLLIN | POLLRDNORM;

  	if (!will_write_block(port))

  		ret |= POLLOUT;
  	if (!port->host_connected)
  		ret |= POLLHUP;
  
  	return ret;
  }

  static void remove_port(struct kref *kref);

  static int port_fops_release(struct inode *inode, struct file *filp)
  {
  	struct port *port;
  
  	port = filp->private_data;
  
  	/* Notify host of port being closed */
  	send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 0);

  	spin_lock_irq(&port->inbuf_lock);

  	port->guest_connected = false;

  	discard_port_data(port);
  
  	spin_unlock_irq(&port->inbuf_lock);

  	spin_lock_irq(&port->outvq_lock);
  	reclaim_consumed_buffers(port);
  	spin_unlock_irq(&port->outvq_lock);

  	/*
  	 * Locks aren't necessary here as a port can't be opened after
  	 * unplug, and if a port isn't unplugged, a kref would already
  	 * exist for the port.  Plus, taking ports_lock here would
  	 * create a dependency on other locks taken by functions
  	 * inside remove_port if we're the last holder of the port,
  	 * creating many problems.
  	 */
  	kref_put(&port->kref, remove_port);

  	return 0;
  }
  
  static int port_fops_open(struct inode *inode, struct file *filp)
  {
  	struct cdev *cdev = inode->i_cdev;
  	struct port *port;

  	int ret;

  	port = find_port_by_devt(cdev->dev);

  	filp->private_data = port;

  	/* Prevent against a port getting hot-unplugged at the same time */
  	spin_lock_irq(&port->portdev->ports_lock);
  	kref_get(&port->kref);
  	spin_unlock_irq(&port->portdev->ports_lock);

  	/*
  	 * Don't allow opening of console port devices -- that's done
  	 * via /dev/hvc
  	 */

  	if (is_console_port(port)) {
  		ret = -ENXIO;
  		goto out;
  	}

  	/* Allow only one process to open a particular port at a time */
  	spin_lock_irq(&port->inbuf_lock);
  	if (port->guest_connected) {
  		spin_unlock_irq(&port->inbuf_lock);

  		ret = -EMFILE;
  		goto out;

  	}
  
  	port->guest_connected = true;
  	spin_unlock_irq(&port->inbuf_lock);

  	spin_lock_irq(&port->outvq_lock);
  	/*
  	 * There might be a chance that we missed reclaiming a few
  	 * buffers in the window of the port getting previously closed
  	 * and opening now.
  	 */
  	reclaim_consumed_buffers(port);
  	spin_unlock_irq(&port->outvq_lock);

  	nonseekable_open(inode, filp);

  	/* Notify host of port being opened */
  	send_control_msg(filp->private_data, VIRTIO_CONSOLE_PORT_OPEN, 1);
  
  	return 0;

  out:

  	kref_put(&port->kref, remove_port);

  	return ret;

  }

  static int port_fops_fasync(int fd, struct file *filp, int mode)
  {
  	struct port *port;
  
  	port = filp->private_data;
  	return fasync_helper(fd, filp, mode, &port->async_queue);
  }

  /*
   * The file operations that we support: programs in the guest can open
   * a console device, read from it, write to it, poll for data and
   * close it.  The devices are at
   *   /dev/vport<device number>p<port number>
   */
  static const struct file_operations port_fops = {
  	.owner = THIS_MODULE,
  	.open  = port_fops_open,
  	.read  = port_fops_read,
  	.write = port_fops_write,
  	.poll  = port_fops_poll,
  	.release = port_fops_release,

  	.fasync = port_fops_fasync,

  	.llseek = no_llseek,

  };

  /*

   * The put_chars() callback is pretty straightforward.

   *

   * We turn the characters into a scatter-gather list, add it to the
   * output queue and then kick the Host.  Then we sit here waiting for
   * it to finish: inefficient in theory, but in practice
   * implementations will do it immediately (lguest's Launcher does).
   */

  static int put_chars(u32 vtermno, const char *buf, int count)
  {

  	struct port *port;

  	if (unlikely(early_put_chars))
  		return early_put_chars(vtermno, buf, count);

  	port = find_port_by_vtermno(vtermno);
  	if (!port)

  		return -EPIPE;

  	return send_buf(port, (void *)buf, count, false);

  }

  /*

   * get_chars() is the callback from the hvc_console infrastructure
   * when an interrupt is received.

   *

   * We call out to fill_readbuf that gets us the required data from the
   * buffers that are queued up.

   */

  static int get_chars(u32 vtermno, char *buf, int count)
  {

  	struct port *port;

  	/* If we've not set up the port yet, we have no input to give. */
  	if (unlikely(early_put_chars))
  		return 0;

  	port = find_port_by_vtermno(vtermno);
  	if (!port)

  		return -EPIPE;

  	/* If we don't have an input queue yet, we can't get input. */

  	BUG_ON(!port->in_vq);

  	return fill_readbuf(port, buf, count, false);

  }

  static void resize_console(struct port *port)

  {

  	struct virtio_device *vdev;

  	/* The port could have been hot-unplugged */

  	if (!port || !is_console_port(port))

  		return;

  	vdev = port->portdev->vdev;

  	if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE))
  		hvc_resize(port->cons.hvc, port->cons.ws);

  }

  /* We set the configuration at this point, since we now have a tty */

  static int notifier_add_vio(struct hvc_struct *hp, int data)
  {

  	struct port *port;
  
  	port = find_port_by_vtermno(hp->vtermno);
  	if (!port)
  		return -EINVAL;

  	hp->irq_requested = 1;

  	resize_console(port);

  	return 0;
  }
  
  static void notifier_del_vio(struct hvc_struct *hp, int data)
  {
  	hp->irq_requested = 0;
  }

  /* The operations for console ports. */

  static const struct hv_ops hv_ops = {

  	.get_chars = get_chars,
  	.put_chars = put_chars,
  	.notifier_add = notifier_add_vio,
  	.notifier_del = notifier_del_vio,
  	.notifier_hangup = notifier_del_vio,
  };
  
  /*
   * Console drivers are initialized very early so boot messages can go
   * out, so we do things slightly differently from the generic virtio
   * initialization of the net and block drivers.
   *
   * At this stage, the console is output-only.  It's too early to set
   * up a virtqueue, so we let the drivers do some boutique early-output
   * thing.
   */
  int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
  {
  	early_put_chars = put_chars;
  	return hvc_instantiate(0, 0, &hv_ops);
  }

  int init_port_console(struct port *port)

  {
  	int ret;
  
  	/*
  	 * The Host's telling us this port is a console port.  Hook it
  	 * up with an hvc console.
  	 *
  	 * To set up and manage our virtual console, we call
  	 * hvc_alloc().
  	 *
  	 * The first argument of hvc_alloc() is the virtual console
  	 * number.  The second argument is the parameter for the
  	 * notification mechanism (like irq number).  We currently
  	 * leave this as zero, virtqueues have implicit notifications.
  	 *
  	 * The third argument is a "struct hv_ops" containing the
  	 * put_chars() get_chars(), notifier_add() and notifier_del()
  	 * pointers.  The final argument is the output buffer size: we
  	 * can do any size, so we put PAGE_SIZE here.
  	 */
  	port->cons.vtermno = pdrvdata.next_vtermno;
  
  	port->cons.hvc = hvc_alloc(port->cons.vtermno, 0, &hv_ops, PAGE_SIZE);
  	if (IS_ERR(port->cons.hvc)) {
  		ret = PTR_ERR(port->cons.hvc);

  		dev_err(port->dev,
  			"error %d allocating hvc for port
  ", ret);

  		port->cons.hvc = NULL;
  		return ret;
  	}
  	spin_lock_irq(&pdrvdata_lock);
  	pdrvdata.next_vtermno++;
  	list_add_tail(&port->cons.list, &pdrvdata.consoles);
  	spin_unlock_irq(&pdrvdata_lock);

  	port->guest_connected = true;

  	/*
  	 * Start using the new console output if this is the first
  	 * console to come up.
  	 */
  	if (early_put_chars)
  		early_put_chars = NULL;

  	/* Notify host of port being opened */
  	send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 1);

  	return 0;
  }

  static ssize_t show_port_name(struct device *dev,
  			      struct device_attribute *attr, char *buffer)
  {
  	struct port *port;
  
  	port = dev_get_drvdata(dev);
  
  	return sprintf(buffer, "%s
  ", port->name);
  }
  
  static DEVICE_ATTR(name, S_IRUGO, show_port_name, NULL);
  
  static struct attribute *port_sysfs_entries[] = {
  	&dev_attr_name.attr,
  	NULL
  };
  
  static struct attribute_group port_attribute_group = {
  	.name = NULL,		/* put in device directory */
  	.attrs = port_sysfs_entries,
  };

  static int debugfs_open(struct inode *inode, struct file *filp)
  {
  	filp->private_data = inode->i_private;
  	return 0;
  }
  
  static ssize_t debugfs_read(struct file *filp, char __user *ubuf,
  			    size_t count, loff_t *offp)
  {
  	struct port *port;
  	char *buf;
  	ssize_t ret, out_offset, out_count;
  
  	out_count = 1024;
  	buf = kmalloc(out_count, GFP_KERNEL);
  	if (!buf)
  		return -ENOMEM;
  
  	port = filp->private_data;
  	out_offset = 0;
  	out_offset += snprintf(buf + out_offset, out_count,
  			       "name: %s
  ", port->name ? port->name : "");
  	out_offset += snprintf(buf + out_offset, out_count - out_offset,
  			       "guest_connected: %d
  ", port->guest_connected);
  	out_offset += snprintf(buf + out_offset, out_count - out_offset,
  			       "host_connected: %d
  ", port->host_connected);
  	out_offset += snprintf(buf + out_offset, out_count - out_offset,

  			       "outvq_full: %d
  ", port->outvq_full);
  	out_offset += snprintf(buf + out_offset, out_count - out_offset,

  			       "bytes_sent: %lu
  ", port->stats.bytes_sent);
  	out_offset += snprintf(buf + out_offset, out_count - out_offset,
  			       "bytes_received: %lu
  ",
  			       port->stats.bytes_received);
  	out_offset += snprintf(buf + out_offset, out_count - out_offset,
  			       "bytes_discarded: %lu
  ",
  			       port->stats.bytes_discarded);
  	out_offset += snprintf(buf + out_offset, out_count - out_offset,

  			       "is_console: %s
  ",
  			       is_console_port(port) ? "yes" : "no");
  	out_offset += snprintf(buf + out_offset, out_count - out_offset,
  			       "console_vtermno: %u
  ", port->cons.vtermno);
  
  	ret = simple_read_from_buffer(ubuf, count, offp, buf, out_offset);
  	kfree(buf);
  	return ret;
  }
  
  static const struct file_operations port_debugfs_ops = {
  	.owner = THIS_MODULE,
  	.open  = debugfs_open,
  	.read  = debugfs_read,
  };

  static void set_console_size(struct port *port, u16 rows, u16 cols)
  {
  	if (!port || !is_console_port(port))
  		return;
  
  	port->cons.ws.ws_row = rows;
  	port->cons.ws.ws_col = cols;
  }

  static unsigned int fill_queue(struct virtqueue *vq, spinlock_t *lock)
  {
  	struct port_buffer *buf;
  	unsigned int nr_added_bufs;
  	int ret;
  
  	nr_added_bufs = 0;
  	do {
  		buf = alloc_buf(PAGE_SIZE);
  		if (!buf)
  			break;
  
  		spin_lock_irq(lock);
  		ret = add_inbuf(vq, buf);
  		if (ret < 0) {
  			spin_unlock_irq(lock);
  			free_buf(buf);
  			break;
  		}
  		nr_added_bufs++;
  		spin_unlock_irq(lock);
  	} while (ret > 0);
  
  	return nr_added_bufs;
  }

  static void send_sigio_to_port(struct port *port)
  {
  	if (port->async_queue && port->guest_connected)
  		kill_fasync(&port->async_queue, SIGIO, POLL_OUT);
  }

  static int add_port(struct ports_device *portdev, u32 id)
  {
  	char debugfs_name[16];
  	struct port *port;
  	struct port_buffer *buf;
  	dev_t devt;
  	unsigned int nr_added_bufs;
  	int err;
  
  	port = kmalloc(sizeof(*port), GFP_KERNEL);
  	if (!port) {
  		err = -ENOMEM;
  		goto fail;
  	}

  	kref_init(&port->kref);

  
  	port->portdev = portdev;
  	port->id = id;
  
  	port->name = NULL;
  	port->inbuf = NULL;
  	port->cons.hvc = NULL;

  	port->async_queue = NULL;

  	port->cons.ws.ws_row = port->cons.ws.ws_col = 0;

  	port->host_connected = port->guest_connected = false;

  	port->stats = (struct port_stats) { 0 };

  	port->outvq_full = false;

  	port->in_vq = portdev->in_vqs[port->id];
  	port->out_vq = portdev->out_vqs[port->id];

  	port->cdev = cdev_alloc();
  	if (!port->cdev) {
  		dev_err(&port->portdev->vdev->dev, "Error allocating cdev
  ");
  		err = -ENOMEM;
  		goto free_port;
  	}
  	port->cdev->ops = &port_fops;

  
  	devt = MKDEV(portdev->chr_major, id);

  	err = cdev_add(port->cdev, devt, 1);

  	if (err < 0) {
  		dev_err(&port->portdev->vdev->dev,
  			"Error %d adding cdev for port %u
  ", err, id);

  		goto free_cdev;

  	}
  	port->dev = device_create(pdrvdata.class, &port->portdev->vdev->dev,
  				  devt, port, "vport%up%u",
  				  port->portdev->drv_index, id);
  	if (IS_ERR(port->dev)) {
  		err = PTR_ERR(port->dev);
  		dev_err(&port->portdev->vdev->dev,
  			"Error %d creating device for port %u
  ",
  			err, id);
  		goto free_cdev;
  	}
  
  	spin_lock_init(&port->inbuf_lock);

  	spin_lock_init(&port->outvq_lock);

  	init_waitqueue_head(&port->waitqueue);
  
  	/* Fill the in_vq with buffers so the host can send us data. */
  	nr_added_bufs = fill_queue(port->in_vq, &port->inbuf_lock);
  	if (!nr_added_bufs) {
  		dev_err(port->dev, "Error allocating inbufs
  ");
  		err = -ENOMEM;
  		goto free_device;
  	}
  
  	/*
  	 * If we're not using multiport support, this has to be a console port
  	 */
  	if (!use_multiport(port->portdev)) {
  		err = init_port_console(port);
  		if (err)
  			goto free_inbufs;
  	}
  
  	spin_lock_irq(&portdev->ports_lock);
  	list_add_tail(&port->list, &port->portdev->ports);
  	spin_unlock_irq(&portdev->ports_lock);
  
  	/*
  	 * Tell the Host we're set so that it can send us various
  	 * configuration parameters for this port (eg, port name,
  	 * caching, whether this is a console port, etc.)
  	 */
  	send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);
  
  	if (pdrvdata.debugfs_dir) {
  		/*
  		 * Finally, create the debugfs file that we can use to
  		 * inspect a port's state at any time
  		 */
  		sprintf(debugfs_name, "vport%up%u",
  			port->portdev->drv_index, id);
  		port->debugfs_file = debugfs_create_file(debugfs_name, 0444,
  							 pdrvdata.debugfs_dir,
  							 port,
  							 &port_debugfs_ops);
  	}
  	return 0;
  
  free_inbufs:
  	while ((buf = virtqueue_detach_unused_buf(port->in_vq)))
  		free_buf(buf);
  free_device:
  	device_destroy(pdrvdata.class, port->dev->devt);
  free_cdev:

  	cdev_del(port->cdev);

  free_port:
  	kfree(port);
  fail:
  	/* The host might want to notify management sw about port add failure */

  	__send_control_msg(portdev, id, VIRTIO_CONSOLE_PORT_READY, 0);

  	return err;
  }

  /* No users remain, remove all port-specific data. */
  static void remove_port(struct kref *kref)
  {
  	struct port *port;
  
  	port = container_of(kref, struct port, kref);
  
  	sysfs_remove_group(&port->dev->kobj, &port_attribute_group);
  	device_destroy(pdrvdata.class, port->dev->devt);
  	cdev_del(port->cdev);
  
  	kfree(port->name);
  
  	debugfs_remove(port->debugfs_file);
  
  	kfree(port);
  }

  static void remove_port_data(struct port *port)
  {
  	struct port_buffer *buf;
  
  	/* Remove unused data this port might have received. */
  	discard_port_data(port);
  
  	reclaim_consumed_buffers(port);
  
  	/* Remove buffers we queued up for the Host to send us data in. */
  	while ((buf = virtqueue_detach_unused_buf(port->in_vq)))
  		free_buf(buf);
  }

  /*
   * Port got unplugged.  Remove port from portdev's list and drop the
   * kref reference.  If no userspace has this port opened, it will
   * result in immediate removal the port.
   */
  static void unplug_port(struct port *port)

  {

  	spin_lock_irq(&port->portdev->ports_lock);
  	list_del(&port->list);
  	spin_unlock_irq(&port->portdev->ports_lock);

  	if (port->guest_connected) {
  		port->guest_connected = false;
  		port->host_connected = false;
  		wake_up_interruptible(&port->waitqueue);

  
  		/* Let the app know the port is going down. */
  		send_sigio_to_port(port);

  	}

  	if (is_console_port(port)) {
  		spin_lock_irq(&pdrvdata_lock);
  		list_del(&port->cons.list);
  		spin_unlock_irq(&pdrvdata_lock);
  		hvc_remove(port->cons.hvc);
  	}

  	remove_port_data(port);

  	/*
  	 * We should just assume the device itself has gone off --
  	 * else a close on an open port later will try to send out a
  	 * control message.
  	 */
  	port->portdev = NULL;

  	/*
  	 * Locks around here are not necessary - a port can't be
  	 * opened after we removed the port struct from ports_list
  	 * above.
  	 */
  	kref_put(&port->kref, remove_port);

  }

  /* Any private messages that the Host and Guest want to share */
  static void handle_control_message(struct ports_device *portdev,
  				   struct port_buffer *buf)
  {
  	struct virtio_console_control *cpkt;
  	struct port *port;

  	size_t name_size;
  	int err;

  
  	cpkt = (struct virtio_console_control *)(buf->buf + buf->offset);
  
  	port = find_port_by_id(portdev, cpkt->id);

  	if (!port && cpkt->event != VIRTIO_CONSOLE_PORT_ADD) {

  		/* No valid header at start of buffer.  Drop it. */
  		dev_dbg(&portdev->vdev->dev,
  			"Invalid index %u in control packet
  ", cpkt->id);
  		return;
  	}
  
  	switch (cpkt->event) {

  	case VIRTIO_CONSOLE_PORT_ADD:
  		if (port) {

  			dev_dbg(&portdev->vdev->dev,
  				"Port %u already added
  ", port->id);

  			send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);
  			break;
  		}
  		if (cpkt->id >= portdev->config.max_nr_ports) {
  			dev_warn(&portdev->vdev->dev,
  				"Request for adding port with out-of-bound id %u, max. supported id: %u
  ",
  				cpkt->id, portdev->config.max_nr_ports - 1);
  			break;
  		}
  		add_port(portdev, cpkt->id);
  		break;
  	case VIRTIO_CONSOLE_PORT_REMOVE:

  		unplug_port(port);

  		break;

  	case VIRTIO_CONSOLE_CONSOLE_PORT:
  		if (!cpkt->value)
  			break;
  		if (is_console_port(port))
  			break;
  
  		init_port_console(port);

  		complete(&early_console_added);

  		/*
  		 * Could remove the port here in case init fails - but
  		 * have to notify the host first.
  		 */
  		break;

  	case VIRTIO_CONSOLE_RESIZE: {
  		struct {
  			__u16 rows;
  			__u16 cols;
  		} size;

  		if (!is_console_port(port))
  			break;

  
  		memcpy(&size, buf->buf + buf->offset + sizeof(*cpkt),
  		       sizeof(size));
  		set_console_size(port, size.rows, size.cols);

  		port->cons.hvc->irq_requested = 1;
  		resize_console(port);
  		break;

  	}

  	case VIRTIO_CONSOLE_PORT_OPEN:
  		port->host_connected = cpkt->value;
  		wake_up_interruptible(&port->waitqueue);

  		/*
  		 * If the host port got closed and the host had any
  		 * unconsumed buffers, we'll be able to reclaim them
  		 * now.
  		 */
  		spin_lock_irq(&port->outvq_lock);
  		reclaim_consumed_buffers(port);
  		spin_unlock_irq(&port->outvq_lock);

  
  		/*
  		 * If the guest is connected, it'll be interested in
  		 * knowing the host connection state changed.
  		 */
  		send_sigio_to_port(port);

  		break;

  	case VIRTIO_CONSOLE_PORT_NAME:
  		/*

  		 * If we woke up after hibernation, we can get this
  		 * again.  Skip it in that case.
  		 */
  		if (port->name)
  			break;
  
  		/*

  		 * Skip the size of the header and the cpkt to get the size
  		 * of the name that was sent
  		 */
  		name_size = buf->len - buf->offset - sizeof(*cpkt) + 1;
  
  		port->name = kmalloc(name_size, GFP_KERNEL);
  		if (!port->name) {
  			dev_err(port->dev,
  				"Not enough space to store port name
  ");
  			break;
  		}
  		strncpy(port->name, buf->buf + buf->offset + sizeof(*cpkt),
  			name_size - 1);
  		port->name[name_size - 1] = 0;
  
  		/*
  		 * Since we only have one sysfs attribute, 'name',
  		 * create it only if we have a name for the port.
  		 */
  		err = sysfs_create_group(&port->dev->kobj,
  					 &port_attribute_group);

  		if (err) {

  			dev_err(port->dev,
  				"Error %d creating sysfs device attributes
  ",
  				err);

  		} else {
  			/*
  			 * Generate a udev event so that appropriate
  			 * symlinks can be created based on udev
  			 * rules.
  			 */
  			kobject_uevent(&port->dev->kobj, KOBJ_CHANGE);
  		}

  		break;

  	}
  }
  
  static void control_work_handler(struct work_struct *work)
  {
  	struct ports_device *portdev;
  	struct virtqueue *vq;
  	struct port_buffer *buf;
  	unsigned int len;
  
  	portdev = container_of(work, struct ports_device, control_work);
  	vq = portdev->c_ivq;
  
  	spin_lock(&portdev->cvq_lock);

  	while ((buf = virtqueue_get_buf(vq, &len))) {

  		spin_unlock(&portdev->cvq_lock);
  
  		buf->len = len;
  		buf->offset = 0;
  
  		handle_control_message(portdev, buf);
  
  		spin_lock(&portdev->cvq_lock);
  		if (add_inbuf(portdev->c_ivq, buf) < 0) {
  			dev_warn(&portdev->vdev->dev,
  				 "Error adding buffer to queue
  ");
  			free_buf(buf);
  		}
  	}
  	spin_unlock(&portdev->cvq_lock);
  }

  static void out_intr(struct virtqueue *vq)
  {
  	struct port *port;
  
  	port = find_port_by_vq(vq->vdev->priv, vq);
  	if (!port)
  		return;
  
  	wake_up_interruptible(&port->waitqueue);
  }

  static void in_intr(struct virtqueue *vq)
  {
  	struct port *port;
  	unsigned long flags;
  
  	port = find_port_by_vq(vq->vdev->priv, vq);
  	if (!port)
  		return;
  
  	spin_lock_irqsave(&port->inbuf_lock, flags);

  	port->inbuf = get_inbuf(port);

  	/*
  	 * Don't queue up data when port is closed.  This condition
  	 * can be reached when a console port is not yet connected (no
  	 * tty is spawned) and the host sends out data to console
  	 * ports.  For generic serial ports, the host won't
  	 * (shouldn't) send data till the guest is connected.
  	 */
  	if (!port->guest_connected)
  		discard_port_data(port);

  	spin_unlock_irqrestore(&port->inbuf_lock, flags);

  	wake_up_interruptible(&port->waitqueue);

  	/* Send a SIGIO indicating new data in case the process asked for it */
  	send_sigio_to_port(port);

  	if (is_console_port(port) && hvc_poll(port->cons.hvc))
  		hvc_kick();
  }
  
  static void control_intr(struct virtqueue *vq)
  {
  	struct ports_device *portdev;
  
  	portdev = vq->vdev->priv;
  	schedule_work(&portdev->control_work);
  }

  static void config_intr(struct virtio_device *vdev)
  {
  	struct ports_device *portdev;
  
  	portdev = vdev->priv;

  	if (!use_multiport(portdev)) {

  		struct port *port;
  		u16 rows, cols;
  
  		vdev->config->get(vdev,
  				  offsetof(struct virtio_console_config, cols),
  				  &cols, sizeof(u16));
  		vdev->config->get(vdev,
  				  offsetof(struct virtio_console_config, rows),
  				  &rows, sizeof(u16));
  
  		port = find_port_by_id(portdev, 0);
  		set_console_size(port, rows, cols);

  		/*
  		 * We'll use this way of resizing only for legacy
  		 * support.  For newer userspace
  		 * (VIRTIO_CONSOLE_F_MULTPORT+), use control messages
  		 * to indicate console size changes so that it can be
  		 * done per-port.
  		 */

  		resize_console(port);

  	}

  }

  static int init_vqs(struct ports_device *portdev)
  {
  	vq_callback_t **io_callbacks;
  	char **io_names;
  	struct virtqueue **vqs;

  	u32 i, j, nr_ports, nr_queues;

  	int err;

  	nr_ports = portdev->config.max_nr_ports;
  	nr_queues = use_multiport(portdev) ? (nr_ports + 1) * 2 : 2;

  
  	vqs = kmalloc(nr_queues * sizeof(struct virtqueue *), GFP_KERNEL);

  	io_callbacks = kmalloc(nr_queues * sizeof(vq_callback_t *), GFP_KERNEL);

  	io_names = kmalloc(nr_queues * sizeof(char *), GFP_KERNEL);

  	portdev->in_vqs = kmalloc(nr_ports * sizeof(struct virtqueue *),
  				  GFP_KERNEL);

  	portdev->out_vqs = kmalloc(nr_ports * sizeof(struct virtqueue *),
  				   GFP_KERNEL);

  	if (!vqs || !io_callbacks || !io_names || !portdev->in_vqs ||

  	    !portdev->out_vqs) {

  		err = -ENOMEM;

  		goto free;

  	}

  	/*
  	 * For backward compat (newer host but older guest), the host
  	 * spawns a console port first and also inits the vqs for port
  	 * 0 before others.
  	 */
  	j = 0;
  	io_callbacks[j] = in_intr;

  	io_callbacks[j + 1] = out_intr;

  	io_names[j] = "input";
  	io_names[j + 1] = "output";
  	j += 2;
  
  	if (use_multiport(portdev)) {
  		io_callbacks[j] = control_intr;
  		io_callbacks[j + 1] = NULL;
  		io_names[j] = "control-i";
  		io_names[j + 1] = "control-o";
  
  		for (i = 1; i < nr_ports; i++) {
  			j += 2;
  			io_callbacks[j] = in_intr;

  			io_callbacks[j + 1] = out_intr;

  			io_names[j] = "input";
  			io_names[j + 1] = "output";
  		}
  	}

  	/* Find the queues. */
  	err = portdev->vdev->config->find_vqs(portdev->vdev, nr_queues, vqs,
  					      io_callbacks,
  					      (const char **)io_names);
  	if (err)

  		goto free;

  	j = 0;

  	portdev->in_vqs[0] = vqs[0];
  	portdev->out_vqs[0] = vqs[1];

  	j += 2;
  	if (use_multiport(portdev)) {
  		portdev->c_ivq = vqs[j];
  		portdev->c_ovq = vqs[j + 1];
  
  		for (i = 1; i < nr_ports; i++) {
  			j += 2;
  			portdev->in_vqs[i] = vqs[j];
  			portdev->out_vqs[i] = vqs[j + 1];
  		}
  	}

  	kfree(io_names);

  	kfree(io_callbacks);

  	kfree(vqs);
  
  	return 0;

  free:

  	kfree(portdev->out_vqs);

  	kfree(portdev->in_vqs);

  	kfree(io_names);
  	kfree(io_callbacks);

  	kfree(vqs);

  	return err;
  }

  static const struct file_operations portdev_fops = {
  	.owner = THIS_MODULE,
  };

  static void remove_vqs(struct ports_device *portdev)
  {
  	portdev->vdev->config->del_vqs(portdev->vdev);
  	kfree(portdev->in_vqs);
  	kfree(portdev->out_vqs);
  }
  
  static void remove_controlq_data(struct ports_device *portdev)
  {
  	struct port_buffer *buf;
  	unsigned int len;
  
  	if (!use_multiport(portdev))
  		return;
  
  	while ((buf = virtqueue_get_buf(portdev->c_ivq, &len)))
  		free_buf(buf);
  
  	while ((buf = virtqueue_detach_unused_buf(portdev->c_ivq)))
  		free_buf(buf);
  }

  /*
   * Once we're further in boot, we get probed like any other virtio
   * device.

   *
   * If the host also supports multiple console ports, we check the
   * config space to see how many ports the host has spawned.  We
   * initialize each port found.

   */
  static int __devinit virtcons_probe(struct virtio_device *vdev)
  {

  	struct ports_device *portdev;
  	int err;

  	bool multiport;

  	bool early = early_put_chars != NULL;
  
  	/* Ensure to read early_put_chars now */
  	barrier();

  
  	portdev = kmalloc(sizeof(*portdev), GFP_KERNEL);
  	if (!portdev) {
  		err = -ENOMEM;
  		goto fail;
  	}
  
  	/* Attach this portdev to this virtio_device, and vice-versa. */
  	portdev->vdev = vdev;
  	vdev->priv = portdev;

  	spin_lock_irq(&pdrvdata_lock);
  	portdev->drv_index = pdrvdata.index++;
  	spin_unlock_irq(&pdrvdata_lock);
  
  	portdev->chr_major = register_chrdev(0, "virtio-portsdev",
  					     &portdev_fops);
  	if (portdev->chr_major < 0) {
  		dev_err(&vdev->dev,
  			"Error %d registering chrdev for device %u
  ",
  			portdev->chr_major, portdev->drv_index);
  		err = portdev->chr_major;
  		goto free;
  	}

  	multiport = false;

  	portdev->config.max_nr_ports = 1;

  	if (virtio_config_val(vdev, VIRTIO_CONSOLE_F_MULTIPORT,
  			      offsetof(struct virtio_console_config,
  				       max_nr_ports),
  			      &portdev->config.max_nr_ports) == 0)

  		multiport = true;

  	err = init_vqs(portdev);
  	if (err < 0) {
  		dev_err(&vdev->dev, "Error %d initializing vqs
  ", err);

  		goto free_chrdev;

  	}

  	spin_lock_init(&portdev->ports_lock);
  	INIT_LIST_HEAD(&portdev->ports);
  
  	if (multiport) {

  		unsigned int nr_added_bufs;

  		spin_lock_init(&portdev->cvq_lock);
  		INIT_WORK(&portdev->control_work, &control_work_handler);

  		nr_added_bufs = fill_queue(portdev->c_ivq, &portdev->cvq_lock);
  		if (!nr_added_bufs) {

  			dev_err(&vdev->dev,
  				"Error allocating buffers for control queue
  ");
  			err = -ENOMEM;
  			goto free_vqs;
  		}

  	} else {
  		/*
  		 * For backward compatibility: Create a console port
  		 * if we're running on older host.
  		 */
  		add_port(portdev, 0);

  	}

  	spin_lock_irq(&pdrvdata_lock);
  	list_add_tail(&portdev->list, &pdrvdata.portdevs);
  	spin_unlock_irq(&pdrvdata_lock);

  	__send_control_msg(portdev, VIRTIO_CONSOLE_BAD_ID,
  			   VIRTIO_CONSOLE_DEVICE_READY, 1);

  
  	/*
  	 * If there was an early virtio console, assume that there are no
  	 * other consoles. We need to wait until the hvc_alloc matches the
  	 * hvc_instantiate, otherwise tty_open will complain, resulting in
  	 * a "Warning: unable to open an initial console" boot failure.
  	 * Without multiport this is done in add_port above. With multiport
  	 * this might take some host<->guest communication - thus we have to
  	 * wait.
  	 */
  	if (multiport && early)
  		wait_for_completion(&early_console_added);

  	return 0;

  free_vqs:

  	/* The host might want to notify mgmt sw about device add failure */
  	__send_control_msg(portdev, VIRTIO_CONSOLE_BAD_ID,
  			   VIRTIO_CONSOLE_DEVICE_READY, 0);

  	remove_vqs(portdev);

  free_chrdev:
  	unregister_chrdev(portdev->chr_major, "virtio-portsdev");

  free:

  	kfree(portdev);

  fail:
  	return err;
  }

  static void virtcons_remove(struct virtio_device *vdev)
  {
  	struct ports_device *portdev;
  	struct port *port, *port2;

  
  	portdev = vdev->priv;

  	spin_lock_irq(&pdrvdata_lock);
  	list_del(&portdev->list);
  	spin_unlock_irq(&pdrvdata_lock);

  	/* Disable interrupts for vqs */
  	vdev->config->reset(vdev);
  	/* Finish up work that's lined up */

  	cancel_work_sync(&portdev->control_work);

  
  	list_for_each_entry_safe(port, port2, &portdev->ports, list)

  		unplug_port(port);

  
  	unregister_chrdev(portdev->chr_major, "virtio-portsdev");

  	/*
  	 * When yanking out a device, we immediately lose the
  	 * (device-side) queues.  So there's no point in keeping the
  	 * guest side around till we drop our final reference.  This
  	 * also means that any ports which are in an open state will
  	 * have to just stop using the port, as the vqs are going
  	 * away.
  	 */

  	remove_controlq_data(portdev);
  	remove_vqs(portdev);

  	kfree(portdev);
  }

  static struct virtio_device_id id_table[] = {
  	{ VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID },
  	{ 0 },
  };

  static unsigned int features[] = {
  	VIRTIO_CONSOLE_F_SIZE,

  	VIRTIO_CONSOLE_F_MULTIPORT,

  };

  #ifdef CONFIG_PM
  static int virtcons_freeze(struct virtio_device *vdev)
  {
  	struct ports_device *portdev;
  	struct port *port;
  
  	portdev = vdev->priv;
  
  	vdev->config->reset(vdev);

  	virtqueue_disable_cb(portdev->c_ivq);

  	cancel_work_sync(&portdev->control_work);

  	/*
  	 * Once more: if control_work_handler() was running, it would
  	 * enable the cb as the last step.
  	 */
  	virtqueue_disable_cb(portdev->c_ivq);

  	remove_controlq_data(portdev);
  
  	list_for_each_entry(port, &portdev->ports, list) {

  		virtqueue_disable_cb(port->in_vq);
  		virtqueue_disable_cb(port->out_vq);

  		/*
  		 * We'll ask the host later if the new invocation has
  		 * the port opened or closed.
  		 */
  		port->host_connected = false;
  		remove_port_data(port);
  	}
  	remove_vqs(portdev);
  
  	return 0;
  }
  
  static int virtcons_restore(struct virtio_device *vdev)
  {
  	struct ports_device *portdev;
  	struct port *port;
  	int ret;
  
  	portdev = vdev->priv;
  
  	ret = init_vqs(portdev);
  	if (ret)
  		return ret;
  
  	if (use_multiport(portdev))
  		fill_queue(portdev->c_ivq, &portdev->cvq_lock);
  
  	list_for_each_entry(port, &portdev->ports, list) {
  		port->in_vq = portdev->in_vqs[port->id];
  		port->out_vq = portdev->out_vqs[port->id];
  
  		fill_queue(port->in_vq, &port->inbuf_lock);
  
  		/* Get port open/close status on the host */
  		send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);
  	}
  	return 0;
  }
  #endif

  static struct virtio_driver virtio_console = {

  	.feature_table = features,
  	.feature_table_size = ARRAY_SIZE(features),

  	.driver.name =	KBUILD_MODNAME,
  	.driver.owner =	THIS_MODULE,
  	.id_table =	id_table,
  	.probe =	virtcons_probe,

  	.remove =	virtcons_remove,

  	.config_changed = config_intr,

  #ifdef CONFIG_PM
  	.freeze =	virtcons_freeze,
  	.restore =	virtcons_restore,
  #endif

  };
  
  static int __init init(void)
  {

  	int err;
  
  	pdrvdata.class = class_create(THIS_MODULE, "virtio-ports");
  	if (IS_ERR(pdrvdata.class)) {
  		err = PTR_ERR(pdrvdata.class);
  		pr_err("Error %d creating virtio-ports class
  ", err);
  		return err;
  	}

  
  	pdrvdata.debugfs_dir = debugfs_create_dir("virtio-ports", NULL);
  	if (!pdrvdata.debugfs_dir) {
  		pr_warning("Error %ld creating debugfs dir for virtio-ports
  ",
  			   PTR_ERR(pdrvdata.debugfs_dir));
  	}

  	INIT_LIST_HEAD(&pdrvdata.consoles);

  	INIT_LIST_HEAD(&pdrvdata.portdevs);

  	return register_virtio_driver(&virtio_console);
  }

  
  static void __exit fini(void)
  {
  	unregister_virtio_driver(&virtio_console);
  
  	class_destroy(pdrvdata.class);
  	if (pdrvdata.debugfs_dir)
  		debugfs_remove_recursive(pdrvdata.debugfs_dir);
  }

  module_init(init);

  module_exit(fini);

  
  MODULE_DEVICE_TABLE(virtio, id_table);
  MODULE_DESCRIPTION("Virtio console driver");
  MODULE_LICENSE("GPL");