#include <linux/virtio.h>
  #include <linux/spinlock.h>
  #include <linux/virtio_config.h>

  #include <linux/module.h>

  #include <linux/idr.h>

  #include <uapi/linux/virtio_ids.h>

  /* Unique numbering for virtio devices. */

  static DEFINE_IDA(virtio_index_ida);

  static ssize_t device_show(struct device *_d,
  			   struct device_attribute *attr, char *buf)
  {

  	struct virtio_device *dev = dev_to_virtio(_d);

  	return sprintf(buf, "0x%04x
  ", dev->id.device);

  }

  static DEVICE_ATTR_RO(device);

  static ssize_t vendor_show(struct device *_d,
  			   struct device_attribute *attr, char *buf)
  {

  	struct virtio_device *dev = dev_to_virtio(_d);

  	return sprintf(buf, "0x%04x
  ", dev->id.vendor);

  }

  static DEVICE_ATTR_RO(vendor);

  static ssize_t status_show(struct device *_d,
  			   struct device_attribute *attr, char *buf)
  {

  	struct virtio_device *dev = dev_to_virtio(_d);

  	return sprintf(buf, "0x%08x
  ", dev->config->get_status(dev));

  }

  static DEVICE_ATTR_RO(status);

  static ssize_t modalias_show(struct device *_d,
  			     struct device_attribute *attr, char *buf)
  {

  	struct virtio_device *dev = dev_to_virtio(_d);

  	return sprintf(buf, "virtio:d%08Xv%08X
  ",
  		       dev->id.device, dev->id.vendor);
  }

  static DEVICE_ATTR_RO(modalias);

  static ssize_t features_show(struct device *_d,
  			     struct device_attribute *attr, char *buf)
  {

  	struct virtio_device *dev = dev_to_virtio(_d);

  	unsigned int i;
  	ssize_t len = 0;
  
  	/* We actually represent this as a bitstring, as it could be
  	 * arbitrary length in future. */

  	for (i = 0; i < sizeof(dev->features)*8; i++)

  		len += sprintf(buf+len, "%c",

  			       __virtio_test_bit(dev, i) ? '1' : '0');

  	len += sprintf(buf+len, "
  ");
  	return len;
  }

  static DEVICE_ATTR_RO(features);
  
  static struct attribute *virtio_dev_attrs[] = {
  	&dev_attr_device.attr,
  	&dev_attr_vendor.attr,
  	&dev_attr_status.attr,
  	&dev_attr_modalias.attr,
  	&dev_attr_features.attr,
  	NULL,

  };

  ATTRIBUTE_GROUPS(virtio_dev);

  
  static inline int virtio_id_match(const struct virtio_device *dev,
  				  const struct virtio_device_id *id)
  {

  	if (id->device != dev->id.device && id->device != VIRTIO_DEV_ANY_ID)

  		return 0;

  	return id->vendor == VIRTIO_DEV_ANY_ID || id->vendor == dev->id.vendor;

  }
  
  /* This looks through all the IDs a driver claims to support.  If any of them
   * match, we return 1 and the kernel will call virtio_dev_probe(). */
  static int virtio_dev_match(struct device *_dv, struct device_driver *_dr)
  {
  	unsigned int i;

  	struct virtio_device *dev = dev_to_virtio(_dv);

  	const struct virtio_device_id *ids;

  	ids = drv_to_virtio(_dr)->id_table;

  	for (i = 0; ids[i].device; i++)
  		if (virtio_id_match(dev, &ids[i]))
  			return 1;
  	return 0;
  }

  static int virtio_uevent(struct device *_dv, struct kobj_uevent_env *env)
  {

  	struct virtio_device *dev = dev_to_virtio(_dv);

  
  	return add_uevent_var(env, "MODALIAS=virtio:d%08Xv%08X",
  			      dev->id.device, dev->id.vendor);
  }

  static void add_status(struct virtio_device *dev, unsigned status)
  {
  	dev->config->set_status(dev, dev->config->get_status(dev) | status);
  }

  void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
  					 unsigned int fbit)
  {
  	unsigned int i;

  	struct virtio_driver *drv = drv_to_virtio(vdev->dev.driver);

  
  	for (i = 0; i < drv->feature_table_size; i++)
  		if (drv->feature_table[i] == fbit)
  			return;

  
  	if (drv->feature_table_legacy) {
  		for (i = 0; i < drv->feature_table_size_legacy; i++)
  			if (drv->feature_table_legacy[i] == fbit)
  				return;
  	}

  	BUG();
  }
  EXPORT_SYMBOL_GPL(virtio_check_driver_offered_feature);

  static void __virtio_config_changed(struct virtio_device *dev)
  {
  	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
  
  	if (!dev->config_enabled)
  		dev->config_change_pending = true;
  	else if (drv && drv->config_changed)
  		drv->config_changed(dev);
  }
  
  void virtio_config_changed(struct virtio_device *dev)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&dev->config_lock, flags);
  	__virtio_config_changed(dev);
  	spin_unlock_irqrestore(&dev->config_lock, flags);
  }
  EXPORT_SYMBOL_GPL(virtio_config_changed);
  
  static void virtio_config_disable(struct virtio_device *dev)
  {
  	spin_lock_irq(&dev->config_lock);
  	dev->config_enabled = false;
  	spin_unlock_irq(&dev->config_lock);
  }
  
  static void virtio_config_enable(struct virtio_device *dev)
  {
  	spin_lock_irq(&dev->config_lock);
  	dev->config_enabled = true;
  	if (dev->config_change_pending)
  		__virtio_config_changed(dev);
  	dev->config_change_pending = false;
  	spin_unlock_irq(&dev->config_lock);
  }

  static int virtio_finalize_features(struct virtio_device *dev)
  {
  	int ret = dev->config->finalize_features(dev);
  	unsigned status;
  
  	if (ret)
  		return ret;
  
  	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
  		return 0;
  
  	add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
  	status = dev->config->get_status(dev);
  	if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
  		dev_err(&dev->dev, "virtio: device refuses features: %x
  ",
  			status);
  		return -ENODEV;
  	}
  	return 0;
  }

  static int virtio_dev_probe(struct device *_d)
  {

  	int err, i;

  	struct virtio_device *dev = dev_to_virtio(_d);

  	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);

  	u64 device_features;

  	u64 driver_features;

  	u64 driver_features_legacy;

  	/* We have a driver! */

  	add_status(dev, VIRTIO_CONFIG_S_DRIVER);

  
  	/* Figure out what features the device supports. */
  	device_features = dev->config->get_features(dev);

  	/* Figure out what features the driver supports. */
  	driver_features = 0;

  	for (i = 0; i < drv->feature_table_size; i++) {
  		unsigned int f = drv->feature_table[i];

  		BUG_ON(f >= 64);

  		driver_features |= (1ULL << f);

  	}

  	/* Some drivers have a separate feature table for virtio v1.0 */
  	if (drv->feature_table_legacy) {
  		driver_features_legacy = 0;
  		for (i = 0; i < drv->feature_table_size_legacy; i++) {
  			unsigned int f = drv->feature_table_legacy[i];
  			BUG_ON(f >= 64);
  			driver_features_legacy |= (1ULL << f);
  		}
  	} else {
  		driver_features_legacy = driver_features;
  	}

  	if (device_features & (1ULL << VIRTIO_F_VERSION_1))

  		dev->features = driver_features & device_features;
  	else
  		dev->features = driver_features_legacy & device_features;

  	/* Transport features always preserved to pass to finalize_features. */

  	for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++)

  		if (device_features & (1ULL << i))

  			__virtio_set_bit(dev, i);

  	err = virtio_finalize_features(dev);

  	if (err)
  		goto err;

  	err = drv->probe(dev);
  	if (err)

  		goto err;

  	/* If probe didn't do it, mark device DRIVER_OK ourselves. */
  	if (!(dev->config->get_status(dev) & VIRTIO_CONFIG_S_DRIVER_OK))
  		virtio_device_ready(dev);

  	if (drv->scan)
  		drv->scan(dev);

  	virtio_config_enable(dev);
  
  	return 0;
  err:
  	add_status(dev, VIRTIO_CONFIG_S_FAILED);

  	return err;

  }

  static int virtio_dev_remove(struct device *_d)
  {

  	struct virtio_device *dev = dev_to_virtio(_d);

  	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);

  	virtio_config_disable(dev);

  	drv->remove(dev);

  
  	/* Driver should have reset device. */

  	WARN_ON_ONCE(dev->config->get_status(dev));

  
  	/* Acknowledge the device's existence again. */
  	add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);

  	return 0;
  }

  static struct bus_type virtio_bus = {
  	.name  = "virtio",
  	.match = virtio_dev_match,

  	.dev_groups = virtio_dev_groups,

  	.uevent = virtio_uevent,
  	.probe = virtio_dev_probe,
  	.remove = virtio_dev_remove,
  };

  int register_virtio_driver(struct virtio_driver *driver)
  {

  	/* Catch this early. */
  	BUG_ON(driver->feature_table_size && !driver->feature_table);

  	driver->driver.bus = &virtio_bus;

  	return driver_register(&driver->driver);
  }
  EXPORT_SYMBOL_GPL(register_virtio_driver);
  
  void unregister_virtio_driver(struct virtio_driver *driver)
  {
  	driver_unregister(&driver->driver);
  }
  EXPORT_SYMBOL_GPL(unregister_virtio_driver);
  
  int register_virtio_device(struct virtio_device *dev)
  {
  	int err;
  
  	dev->dev.bus = &virtio_bus;

  
  	/* Assign a unique device index and hence name. */

  	err = ida_simple_get(&virtio_index_ida, 0, 0, GFP_KERNEL);
  	if (err < 0)
  		goto out;
  
  	dev->index = err;

  	dev_set_name(&dev->dev, "virtio%u", dev->index);

  	spin_lock_init(&dev->config_lock);
  	dev->config_enabled = false;
  	dev->config_change_pending = false;

  	/* We always start by resetting the device, in case a previous
  	 * driver messed it up.  This also tests that code path a little. */
  	dev->config->reset(dev);

  	/* Acknowledge that we've seen the device. */
  	add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);

  	INIT_LIST_HEAD(&dev->vqs);

  	/* device_register() causes the bus infrastructure to look for a
  	 * matching driver. */
  	err = device_register(&dev->dev);

  out:

  	if (err)
  		add_status(dev, VIRTIO_CONFIG_S_FAILED);
  	return err;
  }
  EXPORT_SYMBOL_GPL(register_virtio_device);
  
  void unregister_virtio_device(struct virtio_device *dev)
  {

  	int index = dev->index; /* save for after device release */

  	device_unregister(&dev->dev);

  	ida_simple_remove(&virtio_index_ida, index);

  }
  EXPORT_SYMBOL_GPL(unregister_virtio_device);

  #ifdef CONFIG_PM_SLEEP
  int virtio_device_freeze(struct virtio_device *dev)
  {
  	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);

  	virtio_config_disable(dev);

  	dev->failed = dev->config->get_status(dev) & VIRTIO_CONFIG_S_FAILED;
  
  	if (drv && drv->freeze)
  		return drv->freeze(dev);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(virtio_device_freeze);
  
  int virtio_device_restore(struct virtio_device *dev)
  {
  	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);

  	int ret;

  
  	/* We always start by resetting the device, in case a previous
  	 * driver messed it up. */
  	dev->config->reset(dev);
  
  	/* Acknowledge that we've seen the device. */
  	add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
  
  	/* Maybe driver failed before freeze.
  	 * Restore the failed status, for debugging. */
  	if (dev->failed)
  		add_status(dev, VIRTIO_CONFIG_S_FAILED);
  
  	if (!drv)
  		return 0;
  
  	/* We have a driver! */
  	add_status(dev, VIRTIO_CONFIG_S_DRIVER);

  	ret = virtio_finalize_features(dev);

  	if (ret)
  		goto err;

  
  	if (drv->restore) {

  		ret = drv->restore(dev);
  		if (ret)
  			goto err;

  	}
  
  	/* Finally, tell the device we're all set */
  	add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);

  	virtio_config_enable(dev);

  	return 0;

  
  err:
  	add_status(dev, VIRTIO_CONFIG_S_FAILED);
  	return ret;

  }
  EXPORT_SYMBOL_GPL(virtio_device_restore);
  #endif

  static int virtio_init(void)
  {
  	if (bus_register(&virtio_bus) != 0)
  		panic("virtio bus registration failed");
  	return 0;
  }

  
  static void __exit virtio_exit(void)
  {
  	bus_unregister(&virtio_bus);

  	ida_destroy(&virtio_index_ida);

  }

  core_initcall(virtio_init);

  module_exit(virtio_exit);
  
  MODULE_LICENSE("GPL");