drivers/char/virtio_console.c - kernel/msm-4.9 - Gitiles

 /*
  * Copyright (C) 2006, 2007, 2009 Rusty Russell, IBM Corporation
  *
  * 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/err.h>
 #include <linux/init.h>
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/virtio.h>
 #include <linux/virtio_console.h>
 #include "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 {
 	/*
 	 * 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;

 	/*
 	 * 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;
 };

 /*
  * This is a per-device struct that stores data common to all the
  * ports for that device (vdev->priv).
  */
 struct ports_device {
 	/* Array of per-port IO virtqueues */
 	struct virtqueue **in_vqs, **out_vqs;

 	struct virtio_device *vdev;
 };

 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 struct holds the per-port data */
 struct port {
 	/* 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;

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

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

 /* 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_vq(struct ports_device *portdev,
 				    struct virtqueue *vq)
 {
 	struct port *port;
 	struct console *cons;
 	unsigned long flags;

 	spin_lock_irqsave(&pdrvdata_lock, flags);
 	list_for_each_entry(cons, &pdrvdata.consoles, list) {
 		port = container_of(cons, struct port, cons);
 		if (port->in_vq == vq || port->out_vq == vq)
 			goto out;
 	}
 	port = NULL;
 out:
 	spin_unlock_irqrestore(&pdrvdata_lock, flags);
 	return port;
 }

 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 = vq->vq_ops->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 = vq->vq_ops->add_buf(vq, sg, 0, 1, buf);
 	vq->vq_ops->kick(vq);
 	return ret;
 }

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

 	ret = false;
 	spin_lock_irqsave(&port->inbuf_lock, flags);
 	if (port->inbuf)
 		ret = true;
 	spin_unlock_irqrestore(&port->inbuf_lock, flags);

 	return ret;
 }

 /*
  * 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)
 {
 	struct port_buffer *buf;
 	unsigned long flags;

 	if (!out_count || !port_has_data(port))
 		return 0;

 	buf = port->inbuf;
 	if (out_count > buf->len - buf->offset)
 		out_count = buf->len - buf->offset;

 	memcpy(out_buf, buf->buf + buf->offset, out_count);

 	/* Return the number of bytes actually copied */
 	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->portdev->vdev->dev, "failed add_buf\n");

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

 /*
  * 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 scatterlist sg[1];
 	struct port *port;
 	struct virtqueue *out_vq;
 	unsigned int len;

 	port = find_port_by_vtermno(vtermno);
 	if (!port)
 		return 0;

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

 	out_vq = port->out_vq;
 	/* This is a convenient routine to initialize a single-elem sg list */
 	sg_init_one(sg, buf, count);

 	/* This shouldn't fail: if it does, we lose chars. */
 	if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, port) >= 0) {
 		/* Tell Host to go! */
 		out_vq->vq_ops->kick(out_vq);
 		while (!out_vq->vq_ops->get_buf(out_vq, &len))
 			cpu_relax();
 	}

 	/* We're expected to return the amount of data we wrote: all of it. */
 	return count;
 }

 /*
  * 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;

 	port = find_port_by_vtermno(vtermno);
 	if (!port)
 		return 0;

 	/* 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);
 }

 static void resize_console(struct port *port)
 {
 	struct virtio_device *vdev;
 	struct winsize ws;

 	vdev = port->portdev->vdev;
 	if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE)) {
 		vdev->config->get(vdev,
 				  offsetof(struct virtio_console_config, cols),
 				  &ws.ws_col, sizeof(u16));
 		vdev->config->get(vdev,
 				  offsetof(struct virtio_console_config, rows),
 				  &ws.ws_row, sizeof(u16));
 		hvc_resize(port->cons.hvc, ws);
 	}
 }

 static void virtcons_apply_config(struct virtio_device *vdev)
 {
 	resize_console(find_port_by_vtermno(0));
 }

 /* 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;
 }

 static void hvc_handle_input(struct virtqueue *vq)
 {
 	struct port *port;
 	unsigned long flags;

 	port = find_port_by_vq(vq->vdev->priv, vq);
 	if (!port)
 		return;

 	spin_lock_irqsave(&port->inbuf_lock, flags);
 	port->inbuf = get_inbuf(port);
 	spin_unlock_irqrestore(&port->inbuf_lock, flags);

 	if (hvc_poll(port->cons.hvc))
 		hvc_kick();
 }

 /* The operations for the console. */
 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 __devinit 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);
 		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);

 	return 0;
 }

 static int __devinit add_port(struct ports_device *portdev)
 {
 	struct port *port;
 	struct port_buffer *inbuf;
 	int err;

 	port = kmalloc(sizeof(*port), GFP_KERNEL);
 	if (!port) {
 		err = -ENOMEM;
 		goto fail;
 	}

 	port->portdev = portdev;

 	port->inbuf = NULL;

 	port->in_vq = portdev->in_vqs[0];
 	port->out_vq = portdev->out_vqs[0];

 	spin_lock_init(&port->inbuf_lock);

 	inbuf = alloc_buf(PAGE_SIZE);
 	if (!inbuf) {
 		err = -ENOMEM;
 		goto free_port;
 	}

 	/* Register the input buffer the first time. */
 	add_inbuf(port->in_vq, inbuf);

 	err = init_port_console(port);
 	if (err)
 		goto free_inbuf;

 	return 0;

 free_inbuf:
 	free_buf(inbuf);
 free_port:
 	kfree(port);
 fail:
 	return err;
 }

 static int init_vqs(struct ports_device *portdev)
 {
 	vq_callback_t **io_callbacks;
 	char **io_names;
 	struct virtqueue **vqs;
 	u32 nr_ports, nr_queues;
 	int err;

 	/* We currently only have one port and two queues for that port */
 	nr_ports = 1;
 	nr_queues = 2;

 	vqs = kmalloc(nr_queues * sizeof(struct virtqueue *), GFP_KERNEL);
 	if (!vqs) {
 		err = -ENOMEM;
 		goto fail;
 	}
 	io_callbacks = kmalloc(nr_queues * sizeof(vq_callback_t *), GFP_KERNEL);
 	if (!io_callbacks) {
 		err = -ENOMEM;
 		goto free_vqs;
 	}
 	io_names = kmalloc(nr_queues * sizeof(char *), GFP_KERNEL);
 	if (!io_names) {
 		err = -ENOMEM;
 		goto free_callbacks;
 	}
 	portdev->in_vqs = kmalloc(nr_ports * sizeof(struct virtqueue *),
 				  GFP_KERNEL);
 	if (!portdev->in_vqs) {
 		err = -ENOMEM;
 		goto free_names;
 	}
 	portdev->out_vqs = kmalloc(nr_ports * sizeof(struct virtqueue *),
 				   GFP_KERNEL);
 	if (!portdev->out_vqs) {
 		err = -ENOMEM;
 		goto free_invqs;
 	}

 	io_callbacks[0] = hvc_handle_input;
 	io_callbacks[1] = NULL;
 	io_names[0] = "input";
 	io_names[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_outvqs;

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

 	kfree(io_callbacks);
 	kfree(io_names);
 	kfree(vqs);

 	return 0;

 free_names:
 	kfree(io_names);
 free_callbacks:
 	kfree(io_callbacks);
 free_outvqs:
 	kfree(portdev->out_vqs);
 free_invqs:
 	kfree(portdev->in_vqs);
 free_vqs:
 	kfree(vqs);
 fail:
 	return err;
 }

 /*
  * Once we're further in boot, we get probed like any other virtio
  * device.
  */
 static int __devinit virtcons_probe(struct virtio_device *vdev)
 {
 	struct ports_device *portdev;
 	int err;

 	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;

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

 	/* We only have one port. */
 	err = add_port(portdev);
 	if (err)
 		goto free_vqs;

 	/* Start using the new console output. */
 	early_put_chars = NULL;
 	return 0;

 free_vqs:
 	vdev->config->del_vqs(vdev);
 	kfree(portdev->in_vqs);
 	kfree(portdev->out_vqs);
 free:
 	kfree(portdev);
 fail:
 	return err;
 }

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

 static unsigned int features[] = {
 	VIRTIO_CONSOLE_F_SIZE,
 };

 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,
 	.config_changed = virtcons_apply_config,
 };

 static int __init init(void)
 {
 	INIT_LIST_HEAD(&pdrvdata.consoles);

 	return register_virtio_driver(&virtio_console);
 }
 module_init(init);

 MODULE_DEVICE_TABLE(virtio, id_table);
 MODULE_DESCRIPTION("Virtio console driver");
 MODULE_LICENSE("GPL");
	/*
	* Copyright (C) 2006, 2007, 2009 Rusty Russell, IBM Corporation
	*
	* 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/err.h>
	#include <linux/init.h>
	#include <linux/list.h>
	#include <linux/spinlock.h>
	#include <linux/virtio.h>
	#include <linux/virtio_console.h>
	#include "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 {
	/*
	* 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;

	/*
	* 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;
	};

	/*
	* This is a per-device struct that stores data common to all the
	* ports for that device (vdev->priv).
	*/
	struct ports_device {
	/* Array of per-port IO virtqueues */
	struct virtqueue in_vqs, out_vqs;

	struct virtio_device *vdev;
	};

	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 struct holds the per-port data */
	struct port {
	/* 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;

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

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

	/* 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_vq(struct ports_device portdev,
	struct virtqueue *vq)
	{
	struct port *port;
	struct console *cons;
	unsigned long flags;

	spin_lock_irqsave(&pdrvdata_lock, flags);
	list_for_each_entry(cons, &pdrvdata.consoles, list) {
	port = container_of(cons, struct port, cons);
	if (port->in_vq == vq \|\| port->out_vq == vq)
	goto out;
	}
	port = NULL;
	out:
	spin_unlock_irqrestore(&pdrvdata_lock, flags);
	return port;
	}

	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 = vq->vq_ops->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 = vq->vq_ops->add_buf(vq, sg, 0, 1, buf);
	vq->vq_ops->kick(vq);
	return ret;
	}

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

	ret = false;
	spin_lock_irqsave(&port->inbuf_lock, flags);
	if (port->inbuf)
	ret = true;
	spin_unlock_irqrestore(&port->inbuf_lock, flags);

	return ret;
	}

	/*
	* 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)
	{
	struct port_buffer *buf;
	unsigned long flags;

	if (!out_count \|\| !port_has_data(port))
	return 0;

	buf = port->inbuf;
	if (out_count > buf->len - buf->offset)
	out_count = buf->len - buf->offset;

	memcpy(out_buf, buf->buf + buf->offset, out_count);

	/* Return the number of bytes actually copied */
	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->portdev->vdev->dev, "failed add_buf\n");

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

	/*
	* 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 scatterlist sg[1];
	struct port *port;
	struct virtqueue *out_vq;
	unsigned int len;

	port = find_port_by_vtermno(vtermno);
	if (!port)
	return 0;

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

	out_vq = port->out_vq;
	/* This is a convenient routine to initialize a single-elem sg list */
	sg_init_one(sg, buf, count);

	/* This shouldn't fail: if it does, we lose chars. */
	if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, port) >= 0) {
	/* Tell Host to go! */
	out_vq->vq_ops->kick(out_vq);
	while (!out_vq->vq_ops->get_buf(out_vq, &len))
	cpu_relax();
	}

	/* We're expected to return the amount of data we wrote: all of it. */
	return count;
	}

	/*
	* 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;

	port = find_port_by_vtermno(vtermno);
	if (!port)
	return 0;

	/* 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);
	}

	static void resize_console(struct port *port)
	{
	struct virtio_device *vdev;
	struct winsize ws;

	vdev = port->portdev->vdev;
	if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE)) {
	vdev->config->get(vdev,
	offsetof(struct virtio_console_config, cols),
	&ws.ws_col, sizeof(u16));
	vdev->config->get(vdev,
	offsetof(struct virtio_console_config, rows),
	&ws.ws_row, sizeof(u16));
	hvc_resize(port->cons.hvc, ws);
	}
	}

	static void virtcons_apply_config(struct virtio_device *vdev)
	{
	resize_console(find_port_by_vtermno(0));
	}

	/* 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;
	}

	static void hvc_handle_input(struct virtqueue *vq)
	{
	struct port *port;
	unsigned long flags;

	port = find_port_by_vq(vq->vdev->priv, vq);
	if (!port)
	return;

	spin_lock_irqsave(&port->inbuf_lock, flags);
	port->inbuf = get_inbuf(port);
	spin_unlock_irqrestore(&port->inbuf_lock, flags);

	if (hvc_poll(port->cons.hvc))
	hvc_kick();
	}

	/* The operations for the console. */
	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 __devinit 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);
	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);

	return 0;
	}

	static int __devinit add_port(struct ports_device *portdev)
	{
	struct port *port;
	struct port_buffer *inbuf;
	int err;

	port = kmalloc(sizeof(*port), GFP_KERNEL);
	if (!port) {
	err = -ENOMEM;
	goto fail;
	}

	port->portdev = portdev;

	port->inbuf = NULL;

	port->in_vq = portdev->in_vqs[0];
	port->out_vq = portdev->out_vqs[0];

	spin_lock_init(&port->inbuf_lock);

	inbuf = alloc_buf(PAGE_SIZE);
	if (!inbuf) {
	err = -ENOMEM;
	goto free_port;
	}

	/* Register the input buffer the first time. */
	add_inbuf(port->in_vq, inbuf);

	err = init_port_console(port);
	if (err)
	goto free_inbuf;

	return 0;

	free_inbuf:
	free_buf(inbuf);
	free_port:
	kfree(port);
	fail:
	return err;
	}

	static int init_vqs(struct ports_device *portdev)
	{
	vq_callback_t **io_callbacks;
	char **io_names;
	struct virtqueue **vqs;
	u32 nr_ports, nr_queues;
	int err;

	/* We currently only have one port and two queues for that port */
	nr_ports = 1;
	nr_queues = 2;

	vqs = kmalloc(nr_queues * sizeof(struct virtqueue *), GFP_KERNEL);
	if (!vqs) {
	err = -ENOMEM;
	goto fail;
	}
	io_callbacks = kmalloc(nr_queues * sizeof(vq_callback_t *), GFP_KERNEL);
	if (!io_callbacks) {
	err = -ENOMEM;
	goto free_vqs;
	}
	io_names = kmalloc(nr_queues * sizeof(char *), GFP_KERNEL);
	if (!io_names) {
	err = -ENOMEM;
	goto free_callbacks;
	}
	portdev->in_vqs = kmalloc(nr_ports * sizeof(struct virtqueue *),
	GFP_KERNEL);
	if (!portdev->in_vqs) {
	err = -ENOMEM;
	goto free_names;
	}
	portdev->out_vqs = kmalloc(nr_ports * sizeof(struct virtqueue *),
	GFP_KERNEL);
	if (!portdev->out_vqs) {
	err = -ENOMEM;
	goto free_invqs;
	}

	io_callbacks[0] = hvc_handle_input;
	io_callbacks[1] = NULL;
	io_names[0] = "input";
	io_names[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_outvqs;

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

	kfree(io_callbacks);
	kfree(io_names);
	kfree(vqs);

	return 0;

	free_names:
	kfree(io_names);
	free_callbacks:
	kfree(io_callbacks);
	free_outvqs:
	kfree(portdev->out_vqs);
	free_invqs:
	kfree(portdev->in_vqs);
	free_vqs:
	kfree(vqs);
	fail:
	return err;
	}

	/*
	* Once we're further in boot, we get probed like any other virtio
	* device.
	*/
	static int __devinit virtcons_probe(struct virtio_device *vdev)
	{
	struct ports_device *portdev;
	int err;

	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;

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

	/* We only have one port. */
	err = add_port(portdev);
	if (err)
	goto free_vqs;

	/* Start using the new console output. */
	early_put_chars = NULL;
	return 0;

	free_vqs:
	vdev->config->del_vqs(vdev);
	kfree(portdev->in_vqs);
	kfree(portdev->out_vqs);
	free:
	kfree(portdev);
	fail:
	return err;
	}

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

	static unsigned int features[] = {
	VIRTIO_CONSOLE_F_SIZE,
	};

	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,
	.config_changed = virtcons_apply_config,
	};

	static int __init init(void)
	{
	INIT_LIST_HEAD(&pdrvdata.consoles);

	return register_virtio_driver(&virtio_console);
	}
	module_init(init);

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