[linux-2.6-block.git] / drivers / virtio / virtio.c

#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\n", 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\n", 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\n", 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\n",
		       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, "\n");
	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\n",
			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;

	add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
	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,
};

bool virtio_device_is_legacy_only(struct virtio_device_id id)
{
	return id.device == VIRTIO_ID_BALLOON;
}
EXPORT_SYMBOL_GPL(virtio_device_is_legacy_only);

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);
}
core_initcall(virtio_init);
module_exit(virtio_exit);

MODULE_LICENSE("GPL");
Commit	Line	Data
	1	#include <linux/virtio.h>
	2	#include <linux/spinlock.h>
	3	#include <linux/virtio_config.h>
	4	#include <linux/module.h>
	5	#include <linux/idr.h>
	6	#include <uapi/linux/virtio_ids.h>
	7
	8	/* Unique numbering for virtio devices. */
	9	static DEFINE_IDA(virtio_index_ida);
	10
	11	static ssize_t device_show(struct device *_d,
	12	struct device_attribute attr, char buf)
	13	{
	14	struct virtio_device *dev = dev_to_virtio(_d);
	15	return sprintf(buf, "0x%04x\n", dev->id.device);
	16	}
	17	static DEVICE_ATTR_RO(device);
	18
	19	static ssize_t vendor_show(struct device *_d,
	20	struct device_attribute attr, char buf)
	21	{
	22	struct virtio_device *dev = dev_to_virtio(_d);
	23	return sprintf(buf, "0x%04x\n", dev->id.vendor);
	24	}
	25	static DEVICE_ATTR_RO(vendor);
	26
	27	static ssize_t status_show(struct device *_d,
	28	struct device_attribute attr, char buf)
	29	{
	30	struct virtio_device *dev = dev_to_virtio(_d);
	31	return sprintf(buf, "0x%08x\n", dev->config->get_status(dev));
	32	}
	33	static DEVICE_ATTR_RO(status);
	34
	35	static ssize_t modalias_show(struct device *_d,
	36	struct device_attribute attr, char buf)
	37	{
	38	struct virtio_device *dev = dev_to_virtio(_d);
	39	return sprintf(buf, "virtio:d%08Xv%08X\n",
	40	dev->id.device, dev->id.vendor);
	41	}
	42	static DEVICE_ATTR_RO(modalias);
	43
	44	static ssize_t features_show(struct device *_d,
	45	struct device_attribute attr, char buf)
	46	{
	47	struct virtio_device *dev = dev_to_virtio(_d);
	48	unsigned int i;
	49	ssize_t len = 0;
	50
	51	/* We actually represent this as a bitstring, as it could be
	52	* arbitrary length in future. */
	53	for (i = 0; i < sizeof(dev->features)*8; i++)
	54	len += sprintf(buf+len, "%c",
	55	__virtio_test_bit(dev, i) ? '1' : '0');
	56	len += sprintf(buf+len, "\n");
	57	return len;
	58	}
	59	static DEVICE_ATTR_RO(features);
	60
	61	static struct attribute *virtio_dev_attrs[] = {
	62	&dev_attr_device.attr,
	63	&dev_attr_vendor.attr,
	64	&dev_attr_status.attr,
	65	&dev_attr_modalias.attr,
	66	&dev_attr_features.attr,
	67	NULL,
	68	};
	69	ATTRIBUTE_GROUPS(virtio_dev);
	70
	71	static inline int virtio_id_match(const struct virtio_device *dev,
	72	const struct virtio_device_id *id)
	73	{
	74	if (id->device != dev->id.device && id->device != VIRTIO_DEV_ANY_ID)
	75	return 0;
	76
	77	return id->vendor == VIRTIO_DEV_ANY_ID \|\| id->vendor == dev->id.vendor;
	78	}
	79
	80	/* This looks through all the IDs a driver claims to support. If any of them
	81	* match, we return 1 and the kernel will call virtio_dev_probe(). */
	82	static int virtio_dev_match(struct device _dv, struct device_driver _dr)
	83	{
	84	unsigned int i;
	85	struct virtio_device *dev = dev_to_virtio(_dv);
	86	const struct virtio_device_id *ids;
	87
	88	ids = drv_to_virtio(_dr)->id_table;
	89	for (i = 0; ids[i].device; i++)
	90	if (virtio_id_match(dev, &ids[i]))
	91	return 1;
	92	return 0;
	93	}
	94
	95	static int virtio_uevent(struct device _dv, struct kobj_uevent_env env)
	96	{
	97	struct virtio_device *dev = dev_to_virtio(_dv);
	98
	99	return add_uevent_var(env, "MODALIAS=virtio:d%08Xv%08X",
	100	dev->id.device, dev->id.vendor);
	101	}
	102
	103	static void add_status(struct virtio_device *dev, unsigned status)
	104	{
	105	dev->config->set_status(dev, dev->config->get_status(dev) \| status);
	106	}
	107
	108	void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
	109	unsigned int fbit)
	110	{
	111	unsigned int i;
	112	struct virtio_driver *drv = drv_to_virtio(vdev->dev.driver);
	113
	114	for (i = 0; i < drv->feature_table_size; i++)
	115	if (drv->feature_table[i] == fbit)
	116	return;
	117
	118	if (drv->feature_table_legacy) {
	119	for (i = 0; i < drv->feature_table_size_legacy; i++)
	120	if (drv->feature_table_legacy[i] == fbit)
	121	return;
	122	}
	123
	124	BUG();
	125	}
	126	EXPORT_SYMBOL_GPL(virtio_check_driver_offered_feature);
	127
	128	static void __virtio_config_changed(struct virtio_device *dev)
	129	{
	130	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
	131
	132	if (!dev->config_enabled)
	133	dev->config_change_pending = true;
	134	else if (drv && drv->config_changed)
	135	drv->config_changed(dev);
	136	}
	137
	138	void virtio_config_changed(struct virtio_device *dev)
	139	{
	140	unsigned long flags;
	141
	142	spin_lock_irqsave(&dev->config_lock, flags);
	143	__virtio_config_changed(dev);
	144	spin_unlock_irqrestore(&dev->config_lock, flags);
	145	}
	146	EXPORT_SYMBOL_GPL(virtio_config_changed);
	147
	148	static void virtio_config_disable(struct virtio_device *dev)
	149	{
	150	spin_lock_irq(&dev->config_lock);
	151	dev->config_enabled = false;
	152	spin_unlock_irq(&dev->config_lock);
	153	}
	154
	155	static void virtio_config_enable(struct virtio_device *dev)
	156	{
	157	spin_lock_irq(&dev->config_lock);
	158	dev->config_enabled = true;
	159	if (dev->config_change_pending)
	160	__virtio_config_changed(dev);
	161	dev->config_change_pending = false;
	162	spin_unlock_irq(&dev->config_lock);
	163	}
	164
	165	static int virtio_finalize_features(struct virtio_device *dev)
	166	{
	167	int ret = dev->config->finalize_features(dev);
	168	unsigned status;
	169
	170	if (ret)
	171	return ret;
	172
	173	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
	174	return 0;
	175
	176	add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
	177	status = dev->config->get_status(dev);
	178	if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
	179	dev_err(&dev->dev, "virtio: device refuses features: %x\n",
	180	status);
	181	return -ENODEV;
	182	}
	183	return 0;
	184	}
	185
	186	static int virtio_dev_probe(struct device *_d)
	187	{
	188	int err, i;
	189	struct virtio_device *dev = dev_to_virtio(_d);
	190	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
	191	u64 device_features;
	192	u64 driver_features;
	193	u64 driver_features_legacy;
	194
	195	/* We have a driver! */
	196	add_status(dev, VIRTIO_CONFIG_S_DRIVER);
	197
	198	/* Figure out what features the device supports. */
	199	device_features = dev->config->get_features(dev);
	200
	201	/* Figure out what features the driver supports. */
	202	driver_features = 0;
	203	for (i = 0; i < drv->feature_table_size; i++) {
	204	unsigned int f = drv->feature_table[i];
	205	BUG_ON(f >= 64);
	206	driver_features \|= (1ULL << f);
	207	}
	208
	209	/* Some drivers have a separate feature table for virtio v1.0 */
	210	if (drv->feature_table_legacy) {
	211	driver_features_legacy = 0;
	212	for (i = 0; i < drv->feature_table_size_legacy; i++) {
	213	unsigned int f = drv->feature_table_legacy[i];
	214	BUG_ON(f >= 64);
	215	driver_features_legacy \|= (1ULL << f);
	216	}
	217	} else {
	218	driver_features_legacy = driver_features;
	219	}
	220
	221	if (device_features & (1ULL << VIRTIO_F_VERSION_1))
	222	dev->features = driver_features & device_features;
	223	else
	224	dev->features = driver_features_legacy & device_features;
	225
	226	/* Transport features always preserved to pass to finalize_features. */
	227	for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++)
	228	if (device_features & (1ULL << i))
	229	__virtio_set_bit(dev, i);
	230
	231	err = virtio_finalize_features(dev);
	232	if (err)
	233	goto err;
	234
	235	err = drv->probe(dev);
	236	if (err)
	237	goto err;
	238
	239	add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
	240	if (drv->scan)
	241	drv->scan(dev);
	242
	243	virtio_config_enable(dev);
	244
	245	return 0;
	246	err:
	247	add_status(dev, VIRTIO_CONFIG_S_FAILED);
	248	return err;
	249
	250	}
	251
	252	static int virtio_dev_remove(struct device *_d)
	253	{
	254	struct virtio_device *dev = dev_to_virtio(_d);
	255	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
	256
	257	virtio_config_disable(dev);
	258
	259	drv->remove(dev);
	260
	261	/* Driver should have reset device. */
	262	WARN_ON_ONCE(dev->config->get_status(dev));
	263
	264	/* Acknowledge the device's existence again. */
	265	add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
	266	return 0;
	267	}
	268
	269	static struct bus_type virtio_bus = {
	270	.name = "virtio",
	271	.match = virtio_dev_match,
	272	.dev_groups = virtio_dev_groups,
	273	.uevent = virtio_uevent,
	274	.probe = virtio_dev_probe,
	275	.remove = virtio_dev_remove,
	276	};
	277
	278	bool virtio_device_is_legacy_only(struct virtio_device_id id)
	279	{
	280	return id.device == VIRTIO_ID_BALLOON;
	281	}
	282	EXPORT_SYMBOL_GPL(virtio_device_is_legacy_only);
	283
	284	int register_virtio_driver(struct virtio_driver *driver)
	285	{
	286	/* Catch this early. */
	287	BUG_ON(driver->feature_table_size && !driver->feature_table);
	288	driver->driver.bus = &virtio_bus;
	289	return driver_register(&driver->driver);
	290	}
	291	EXPORT_SYMBOL_GPL(register_virtio_driver);
	292
	293	void unregister_virtio_driver(struct virtio_driver *driver)
	294	{
	295	driver_unregister(&driver->driver);
	296	}
	297	EXPORT_SYMBOL_GPL(unregister_virtio_driver);
	298
	299	int register_virtio_device(struct virtio_device *dev)
	300	{
	301	int err;
	302
	303	dev->dev.bus = &virtio_bus;
	304
	305	/* Assign a unique device index and hence name. */
	306	err = ida_simple_get(&virtio_index_ida, 0, 0, GFP_KERNEL);
	307	if (err < 0)
	308	goto out;
	309
	310	dev->index = err;
	311	dev_set_name(&dev->dev, "virtio%u", dev->index);
	312
	313	spin_lock_init(&dev->config_lock);
	314	dev->config_enabled = false;
	315	dev->config_change_pending = false;
	316
	317	/* We always start by resetting the device, in case a previous
	318	* driver messed it up. This also tests that code path a little. */
	319	dev->config->reset(dev);
	320
	321	/* Acknowledge that we've seen the device. */
	322	add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
	323
	324	INIT_LIST_HEAD(&dev->vqs);
	325
	326	/* device_register() causes the bus infrastructure to look for a
	327	* matching driver. */
	328	err = device_register(&dev->dev);
	329	out:
	330	if (err)
	331	add_status(dev, VIRTIO_CONFIG_S_FAILED);
	332	return err;
	333	}
	334	EXPORT_SYMBOL_GPL(register_virtio_device);
	335
	336	void unregister_virtio_device(struct virtio_device *dev)
	337	{
	338	int index = dev->index; /* save for after device release */
	339
	340	device_unregister(&dev->dev);
	341	ida_simple_remove(&virtio_index_ida, index);
	342	}
	343	EXPORT_SYMBOL_GPL(unregister_virtio_device);
	344
	345	#ifdef CONFIG_PM_SLEEP
	346	int virtio_device_freeze(struct virtio_device *dev)
	347	{
	348	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
	349
	350	virtio_config_disable(dev);
	351
	352	dev->failed = dev->config->get_status(dev) & VIRTIO_CONFIG_S_FAILED;
	353
	354	if (drv && drv->freeze)
	355	return drv->freeze(dev);
	356
	357	return 0;
	358	}
	359	EXPORT_SYMBOL_GPL(virtio_device_freeze);
	360
	361	int virtio_device_restore(struct virtio_device *dev)
	362	{
	363	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
	364	int ret;
	365
	366	/* We always start by resetting the device, in case a previous
	367	* driver messed it up. */
	368	dev->config->reset(dev);
	369
	370	/* Acknowledge that we've seen the device. */
	371	add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
	372
	373	/* Maybe driver failed before freeze.
	374	* Restore the failed status, for debugging. */
	375	if (dev->failed)
	376	add_status(dev, VIRTIO_CONFIG_S_FAILED);
	377
	378	if (!drv)
	379	return 0;
	380
	381	/* We have a driver! */
	382	add_status(dev, VIRTIO_CONFIG_S_DRIVER);
	383
	384	ret = virtio_finalize_features(dev);
	385	if (ret)
	386	goto err;
	387
	388	if (drv->restore) {
	389	ret = drv->restore(dev);
	390	if (ret)
	391	goto err;
	392	}
	393
	394	/* Finally, tell the device we're all set */
	395	add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
	396
	397	virtio_config_enable(dev);
	398
	399	return 0;
	400
	401	err:
	402	add_status(dev, VIRTIO_CONFIG_S_FAILED);
	403	return ret;
	404	}
	405	EXPORT_SYMBOL_GPL(virtio_device_restore);
	406	#endif
	407
	408	static int virtio_init(void)
	409	{
	410	if (bus_register(&virtio_bus) != 0)
	411	panic("virtio bus registration failed");
	412	return 0;
	413	}
	414
	415	static void __exit virtio_exit(void)
	416	{
	417	bus_unregister(&virtio_bus);
	418	}
	419	core_initcall(virtio_init);
	420	module_exit(virtio_exit);
	421
	422	MODULE_LICENSE("GPL");