virtio: console: Move file back to drivers/char/

Commit 728674a7e466628df2aeec6d11a2ae1ef968fb67 moved virtio_console.c
to drivers/tty/hvc/ under the perception of this being an hvc driver.
It was such once, but these days it has generic communication
capabilities as well, so move it to drivers/char/.

In the future, the hvc part from this file can be split off and moved
under drivers/tty/hvc/.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
CC: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 1838 insertions, 0 deletions

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
new file mode 100644
index 0000000..5feadee
--- /dev/null
+++ b/drivers/char/virtio_console.c
@@ -0,0 +1,1838 @@
+/*
+ * Copyright (C) 2006, 2007, 2009 Rusty Russell, IBM Corporation
+ * Copyright (C) 2009, 2010 Red Hat, Inc.
+ *
+ * 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/device.h>
+#include <linux/err.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 "../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);
+
+/* 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;
+};
+
+/* 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;
+
+	/*
+	 * 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 void *get_inbuf(struct port *port)
+{
+	struct port_buffer *buf;
+	struct virtqueue *vq;
+	unsigned int len;
+
+	vq = port->in_vq;
+	buf = virtqueue_get_buf(vq, &len);
+	if (buf) {
+		buf->len = len;
+		buf->offset = 0;
+	}
+	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);
+	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;
+	struct virtqueue *vq;
+	unsigned int len;
+	int ret;
+
+	vq = port->in_vq;
+	if (port->inbuf)
+		buf = port->inbuf;
+	else
+		buf = virtqueue_get_buf(vq, &len);
+
+	ret = 0;
+	while (buf) {
+		if (add_inbuf(vq, buf) < 0) {
+			ret++;
+			free_buf(buf);
+		}
+		buf = virtqueue_get_buf(vq, &len);
+	}
+	port->inbuf = NULL;
+	if (ret)
+		dev_warn(port->dev, "Errors adding %d buffers back to vq\n",
+			 ret);
+}
+
+static bool port_has_data(struct port *port)
+{
+	unsigned long flags;
+	bool ret;
+
+	spin_lock_irqsave(&port->inbuf_lock, flags);
+	if (port->inbuf) {
+		ret = true;
+		goto out;
+	}
+	port->inbuf = get_inbuf(port);
+	if (port->inbuf) {
+		ret = true;
+		goto out;
+	}
+	ret = false;
+out:
+	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) >= 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;
+
+	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);
+
+	/* 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);
+	/*
+	 * 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\n");
+
+		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_interruptible(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_interruptible(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\n", 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\n", 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\n", port->name ? port->name : "");
+	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+			       "guest_connected: %d\n", port->guest_connected);
+	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+			       "host_connected: %d\n", port->host_connected);
+	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+			       "outvq_full: %d\n", port->outvq_full);
+	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+			       "is_console: %s\n",
+			       is_console_port(port) ? "yes" : "no");
+	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+			       "console_vtermno: %u\n", 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->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\n");
+		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\n", 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\n",
+			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\n");
+		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);
+}
+
+/*
+ * 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)
+{
+	struct port_buffer *buf;
+
+	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);
+#if 0
+		/*
+		 * hvc_remove() not called as removing one hvc port
+		 * results in other hvc ports getting frozen.
+		 *
+		 * Once this is resolved in hvc, this functionality
+		 * will be enabled.  Till that is done, the -EPIPE
+		 * return from get_chars() above will help
+		 * hvc_console.c to clean up on ports we remove here.
+		 */
+		hvc_remove(port->cons.hvc);
+#endif
+	}
+
+	/* 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);
+
+	/*
+	 * 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\n", cpkt->id);
+		return;
+	}
+
+	switch (cpkt->event) {
+	case VIRTIO_CONSOLE_PORT_ADD:
+		if (port) {
+			dev_dbg(&portdev->vdev->dev,
+				"Port %u already added\n", 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\n",
+				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);
+		/*
+		 * 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:
+		/*
+		 * 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\n");
+			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\n",
+				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\n");
+			free_buf(buf);
+		}
+	}
+	spin_unlock(&portdev->cvq_lock);
+}
+
+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);
+	if (!port->inbuf)
+		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] = NULL;
+	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] = NULL;
+			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,
+};
+
+/*
+ * 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;
+
+	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\n",
+			portdev->chr_major, portdev->drv_index);
+		err = portdev->chr_major;
+		goto free;
+	}
+
+	multiport = false;
+	portdev->config.max_nr_ports = 1;
+	if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_MULTIPORT)) {
+		multiport = true;
+		vdev->features[0] |= 1 << VIRTIO_CONSOLE_F_MULTIPORT;
+
+		vdev->config->get(vdev, offsetof(struct virtio_console_config,
+						 max_nr_ports),
+				  &portdev->config.max_nr_ports,
+				  sizeof(portdev->config.max_nr_ports));
+	}
+
+	/* Let the Host know we support multiple ports.*/
+	vdev->config->finalize_features(vdev);
+
+	err = init_vqs(portdev);
+	if (err < 0) {
+		dev_err(&vdev->dev, "Error %d initializing vqs\n", 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\n");
+			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);
+	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);
+	vdev->config->del_vqs(vdev);
+	kfree(portdev->in_vqs);
+	kfree(portdev->out_vqs);
+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.
+	 */
+	if (use_multiport(portdev)) {
+		struct port_buffer *buf;
+		unsigned int len;
+
+		while ((buf = virtqueue_get_buf(portdev->c_ivq, &len)))
+			free_buf(buf);
+
+		while ((buf = virtqueue_detach_unused_buf(portdev->c_ivq)))
+			free_buf(buf);
+	}
+
+	vdev->config->del_vqs(vdev);
+	kfree(portdev->in_vqs);
+	kfree(portdev->out_vqs);
+
+	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,
+};
+
+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,
+};
+
+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\n", 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\n",
+			   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");