1 files changed, 1850 insertions, 0 deletions

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
new file mode 100644
index 000000000000..490393186338
--- /dev/null
+++ b/drivers/char/virtio_console.c
@@ -0,0 +1,1850 @@
+/*
+ * 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/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 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);
+        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] = 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,
+};
+
+/*
+ * 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");