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>

2 files changed, 1839 insertions, 0 deletions

diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index 5bc765d4c3c..8238f89f73c 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -30,6 +30,7 @@ obj-$(CONFIG_SYNCLINK_GT)	+= synclink_gt.o
 obj-$(CONFIG_AMIGA_BUILTIN_SERIAL) += amiserial.o
 obj-$(CONFIG_SX)		+= sx.o generic_serial.o
 obj-$(CONFIG_RIO)		+= rio/ generic_serial.o
+obj-$(CONFIG_VIRTIO_CONSOLE)	+= virtio_console.o
 obj-$(CONFIG_RAW_DRIVER)	+= raw.o
 obj-$(CONFIG_SGI_SNSC)		+= snsc.o snsc_event.o
 obj-$(CONFIG_MSPEC)		+= mspec.o
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
new file mode 100644
index 00000000000..5feadeefef3
--- /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(po