gst/gstdeviceprovider.c - imx-gstreamer - Git at Google

 /* GStreamer
  * Copyright (C) 2012 Olivier Crete <olivier.crete@collabora.com>
  *
  * gstdeviceprovider.c: Device probing and monitoring
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library 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
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public
  * License along with this library; if not, write to the
  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  * Boston, MA 02111-1307, USA.
  */

 /**
  * SECTION:gstdeviceprovider
  * @short_description: A device provider
  * @see_also: #GstDevice, #GstDeviceMonitor
  *
  * A #GstDeviceProvider subclass is provided by a plugin that handles devices
  * if there is a way to programatically list connected devices. It can also
  * optionally provide updates to the list of connected devices.
  *
  * Each #GstDeviceProvider subclass is a singleton, a plugin should
  * normally provide a single subclass for all devices.
  *
  * Applications would normally use a #GstDeviceMonitor to monitor devices
  * from all relevant providers.
  *
  * Since: 1.4
  */

 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif

 #include "gst_private.h"

 #include "gstdeviceprovider.h"

 #include "gstelementmetadata.h"
 #include "gstquark.h"

 struct _GstDeviceProviderPrivate
 {
   GstBus *bus;

   GMutex start_lock;

   gboolean started_count;
 };

 /* this is used in gstelementfactory.c:gst_element_register() */
 GQuark __gst_deviceproviderclass_factory = 0;

 static void gst_device_provider_class_init (GstDeviceProviderClass * klass);
 static void gst_device_provider_init (GstDeviceProvider * element);
 static void gst_device_provider_base_class_init (gpointer g_class);
 static void gst_device_provider_base_class_finalize (gpointer g_class);
 static void gst_device_provider_dispose (GObject * object);
 static void gst_device_provider_finalize (GObject * object);

 static gpointer gst_device_provider_parent_class = NULL;

 GType
 gst_device_provider_get_type (void)
 {
   static volatile gsize gst_device_provider_type = 0;

   if (g_once_init_enter (&gst_device_provider_type)) {
     GType _type;
     static const GTypeInfo element_info = {
       sizeof (GstDeviceProviderClass),
       gst_device_provider_base_class_init,
       gst_device_provider_base_class_finalize,
       (GClassInitFunc) gst_device_provider_class_init,
       NULL,
       NULL,
       sizeof (GstDeviceProvider),
       0,
       (GInstanceInitFunc) gst_device_provider_init,
       NULL
     };

     _type = g_type_register_static (GST_TYPE_OBJECT, "GstDeviceProvider",
         &element_info, G_TYPE_FLAG_ABSTRACT);

     __gst_deviceproviderclass_factory =
         g_quark_from_static_string ("GST_DEVICEPROVIDERCLASS_FACTORY");
     g_once_init_leave (&gst_device_provider_type, _type);
   }
   return gst_device_provider_type;
 }

 static void
 gst_device_provider_base_class_init (gpointer g_class)
 {
   GstDeviceProviderClass *klass = GST_DEVICE_PROVIDER_CLASS (g_class);

   /* Copy the element details here so elements can inherit the
    * details from their base class and classes only need to set
    * the details in class_init instead of base_init */
   klass->metadata =
       klass->metadata ? gst_structure_copy (klass->metadata) :
       gst_structure_new_empty ("metadata");

   klass->factory = g_type_get_qdata (G_TYPE_FROM_CLASS (klass),
       __gst_deviceproviderclass_factory);
 }

 static void
 gst_device_provider_base_class_finalize (gpointer g_class)
 {
   GstDeviceProviderClass *klass = GST_DEVICE_PROVIDER_CLASS (g_class);

   gst_structure_free (klass->metadata);
 }

 static void
 gst_device_provider_class_init (GstDeviceProviderClass * klass)
 {
   GObjectClass *gobject_class = (GObjectClass *) klass;

   gst_device_provider_parent_class = g_type_class_peek_parent (klass);

   g_type_class_add_private (klass, sizeof (GstDeviceProviderPrivate));

   gobject_class->dispose = gst_device_provider_dispose;
   gobject_class->finalize = gst_device_provider_finalize;
 }

 static void
 gst_device_provider_init (GstDeviceProvider * provider)
 {
   provider->priv = G_TYPE_INSTANCE_GET_PRIVATE (provider,
       GST_TYPE_DEVICE_PROVIDER, GstDeviceProviderPrivate);

   g_mutex_init (&provider->priv->start_lock);

   provider->priv->bus = gst_bus_new ();
   gst_bus_set_flushing (provider->priv->bus, TRUE);
 }


 static void
 gst_device_provider_dispose (GObject * object)
 {
   GstDeviceProvider *provider = GST_DEVICE_PROVIDER (object);

   gst_object_replace ((GstObject **) & provider->priv->bus, NULL);

   GST_OBJECT_LOCK (provider);
   g_list_free_full (provider->devices, (GDestroyNotify) gst_object_unparent);
   provider->devices = NULL;
   GST_OBJECT_UNLOCK (provider);

   G_OBJECT_CLASS (gst_device_provider_parent_class)->dispose (object);
 }

 static void
 gst_device_provider_finalize (GObject * object)
 {
   GstDeviceProvider *provider = GST_DEVICE_PROVIDER (object);

   g_mutex_clear (&provider->priv->start_lock);

   G_OBJECT_CLASS (gst_device_provider_parent_class)->finalize (object);
 }

 /**
  * gst_device_provider_class_add_metadata:
  * @klass: class to set metadata for
  * @key: the key to set
  * @value: the value to set
  *
  * Set @key with @value as metadata in @klass.
  */
 void
 gst_device_provider_class_add_metadata (GstDeviceProviderClass * klass,
     const gchar * key, const gchar * value)
 {
   g_return_if_fail (GST_IS_DEVICE_PROVIDER_CLASS (klass));
   g_return_if_fail (key != NULL);
   g_return_if_fail (value != NULL);

   gst_structure_set ((GstStructure *) klass->metadata,
       key, G_TYPE_STRING, value, NULL);
 }

 /**
  * gst_device_provider_class_add_static_metadata:
  * @klass: class to set metadata for
  * @key: the key to set
  * @value: the value to set
  *
  * Set @key with @value as metadata in @klass.
  *
  * Same as gst_device_provider_class_add_metadata(), but @value must be a static string
  * or an inlined string, as it will not be copied. (GStreamer plugins will
  * be made resident once loaded, so this function can be used even from
  * dynamically loaded plugins.)
  *
  * Since: 1.4
  */
 void
 gst_device_provider_class_add_static_metadata (GstDeviceProviderClass * klass,
     const gchar * key, const gchar * value)
 {
   GValue val = G_VALUE_INIT;

   g_return_if_fail (GST_IS_DEVICE_PROVIDER_CLASS (klass));
   g_return_if_fail (key != NULL);
   g_return_if_fail (value != NULL);

   g_value_init (&val, G_TYPE_STRING);
   g_value_set_static_string (&val, value);
   gst_structure_take_value ((GstStructure *) klass->metadata, key, &val);
 }

 /**
  * gst_device_provider_class_set_metadata:
  * @klass: class to set metadata for
  * @longname: The long English name of the device provider. E.g. "File Sink"
  * @classification: String describing the type of device provider, as an
  *  unordered list separated with slashes ('/'). See draft-klass.txt of the
  *  design docs
  * for more details and common types. E.g: "Sink/File"
  * @description: Sentence describing the purpose of the device provider.
  * E.g: "Write stream to a file"
  * @author: Name and contact details of the author(s). Use \n to separate
  * multiple author metadata. E.g: "Joe Bloggs &lt;joe.blogs at foo.com&gt;"
  *
  * Sets the detailed information for a #GstDeviceProviderClass.
  * <note>This function is for use in _class_init functions only.</note>
  *
  * Since: 1.4
  */
 void
 gst_device_provider_class_set_metadata (GstDeviceProviderClass * klass,
     const gchar * longname, const gchar * classification,
     const gchar * description, const gchar * author)
 {
   g_return_if_fail (GST_IS_DEVICE_PROVIDER_CLASS (klass));
   g_return_if_fail (longname != NULL && *longname != '\0');
   g_return_if_fail (classification != NULL && *classification != '\0');
   g_return_if_fail (description != NULL && *description != '\0');
   g_return_if_fail (author != NULL && *author != '\0');

   gst_structure_id_set ((GstStructure *) klass->metadata,
       GST_QUARK (ELEMENT_METADATA_LONGNAME), G_TYPE_STRING, longname,
       GST_QUARK (ELEMENT_METADATA_KLASS), G_TYPE_STRING, classification,
       GST_QUARK (ELEMENT_METADATA_DESCRIPTION), G_TYPE_STRING, description,
       GST_QUARK (ELEMENT_METADATA_AUTHOR), G_TYPE_STRING, author, NULL);
 }

 /**
  * gst_device_provider_class_set_static_metadata:
  * @klass: class to set metadata for
  * @longname: The long English name of the element. E.g. "File Sink"
  * @classification: String describing the type of element, as an unordered list
  * separated with slashes ('/'). See draft-klass.txt of the design docs
  * for more details and common types. E.g: "Sink/File"
  * @description: Sentence describing the purpose of the element.
  * E.g: "Write stream to a file"
  * @author: Name and contact details of the author(s). Use \n to separate
  * multiple author metadata. E.g: "Joe Bloggs &lt;joe.blogs at foo.com&gt;"
  *
  * Sets the detailed information for a #GstDeviceProviderClass.
  * <note>This function is for use in _class_init functions only.</note>
  *
  * Same as gst_device_provider_class_set_metadata(), but @longname, @classification,
  * @description, and @author must be static strings or inlined strings, as
  * they will not be copied. (GStreamer plugins will be made resident once
  * loaded, so this function can be used even from dynamically loaded plugins.)
  *
  * Since: 1.4
  */
 void
 gst_device_provider_class_set_static_metadata (GstDeviceProviderClass * klass,
     const gchar * longname, const gchar * classification,
     const gchar * description, const gchar * author)
 {
   GstStructure *s = (GstStructure *) klass->metadata;
   GValue val = G_VALUE_INIT;

   g_return_if_fail (GST_IS_DEVICE_PROVIDER_CLASS (klass));
   g_return_if_fail (longname != NULL && *longname != '\0');
   g_return_if_fail (classification != NULL && *classification != '\0');
   g_return_if_fail (description != NULL && *description != '\0');
   g_return_if_fail (author != NULL && *author != '\0');

   g_value_init (&val, G_TYPE_STRING);

   g_value_set_static_string (&val, longname);
   gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_LONGNAME), &val);

   g_value_set_static_string (&val, classification);
   gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_KLASS), &val);

   g_value_set_static_string (&val, description);
   gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_DESCRIPTION),
       &val);

   g_value_set_static_string (&val, author);
   gst_structure_id_take_value (s, GST_QUARK (ELEMENT_METADATA_AUTHOR), &val);
 }

 /**
  * gst_device_provider_class_get_metadata:
  * @klass: class to get metadata for
  * @key: the key to get
  *
  * Get metadata with @key in @klass.
  *
  * Returns: the metadata for @key.
  *
  * Since: 1.4
  */
 const gchar *
 gst_device_provider_class_get_metadata (GstDeviceProviderClass * klass,
     const gchar * key)
 {
   g_return_val_if_fail (GST_IS_DEVICE_PROVIDER_CLASS (klass), NULL);
   g_return_val_if_fail (key != NULL, NULL);

   return gst_structure_get_string ((GstStructure *) klass->metadata, key);
 }

 /**
  * gst_device_provider_get_devices:
  * @provider: A #GstDeviceProvider
  *
  * Gets a list of devices that this provider understands. This may actually
  * probe the hardware if the provider is not currently started.
  *
  * Returns: (transfer full) (element-type GstDevice): a #GList of
  *   #GstDevice
  *
  * Since: 1.4
  */

 GList *
 gst_device_provider_get_devices (GstDeviceProvider * provider)
 {
   GstDeviceProviderClass *klass;
   GList *devices = NULL;
   gboolean started;
   GList *item;

   g_return_val_if_fail (GST_IS_DEVICE_PROVIDER (provider), NULL);
   klass = GST_DEVICE_PROVIDER_GET_CLASS (provider);

   g_mutex_lock (&provider->priv->start_lock);
   started = (provider->priv->started_count > 0);

   if (started) {
     GST_OBJECT_LOCK (provider);
     for (item = provider->devices; item; item = item->next)
       devices = g_list_prepend (devices, gst_object_ref (item->data));
     GST_OBJECT_UNLOCK (provider);
   } else if (klass->probe)
     devices = klass->probe (provider);

   g_mutex_unlock (&provider->priv->start_lock);

   return devices;
 }

 /**
  * gst_device_provider_start:
  * @provider: A #GstDeviceProvider
  *
  * Starts providering the devices. This will cause #GST_MESSAGE_DEVICE messages
  * to be posted on the provider's bus when devices are added or removed from
  * the system.
  *
  * Since the #GstDeviceProvider is a singleton,
  * gst_device_provider_start() may already have been called by another
  * user of the object, gst_device_provider_stop() needs to be called the same
  * number of times.
  *
  * Returns: %TRUE if the device providering could be started
  *
  * Since: 1.4
  */

 gboolean
 gst_device_provider_start (GstDeviceProvider * provider)
 {
   GstDeviceProviderClass *klass;
   gboolean ret = FALSE;

   g_return_val_if_fail (GST_IS_DEVICE_PROVIDER (provider), FALSE);
   klass = GST_DEVICE_PROVIDER_GET_CLASS (provider);

   g_mutex_lock (&provider->priv->start_lock);

   if (provider->priv->started_count > 0) {
     ret = TRUE;
     goto started;
   }

   if (klass->start)
     ret = klass->start (provider);

   if (ret) {
     provider->priv->started_count++;
     gst_bus_set_flushing (provider->priv->bus, FALSE);
   }

 started:

   g_mutex_unlock (&provider->priv->start_lock);

   return ret;
 }

 /**
  * gst_device_provider_stop:
  * @provider: A #GstDeviceProvider
  *
  * Decreases the use-count by one. If the use count reaches zero, this
  * #GstDeviceProvider will stop providering the devices. This needs to be
  * called the same number of times that gst_device_provider_start() was called.
  *
  * Since: 1.4
  */

 void
 gst_device_provider_stop (GstDeviceProvider * provider)
 {
   GstDeviceProviderClass *klass;

   g_return_if_fail (GST_IS_DEVICE_PROVIDER (provider));
   klass = GST_DEVICE_PROVIDER_GET_CLASS (provider);

   g_mutex_lock (&provider->priv->start_lock);

   if (provider->priv->started_count == 1) {
     gst_bus_set_flushing (provider->priv->bus, TRUE);
     if (klass->stop)
       klass->stop (provider);
     GST_OBJECT_LOCK (provider);
     g_list_free_full (provider->devices, (GDestroyNotify) gst_object_unparent);
     provider->devices = NULL;
     GST_OBJECT_UNLOCK (provider);
   } else if (provider->priv->started_count < 1) {
     g_critical
         ("Trying to stop a GstDeviceProvider %s which is already stopped",
         GST_OBJECT_NAME (provider));
   }

   provider->priv->started_count--;
   g_mutex_unlock (&provider->priv->start_lock);
 }


 /**
  * gst_device_provider_get_factory:
  * @provider: a #GstDeviceProvider to request the device provider factory of.
  *
  * Retrieves the factory that was used to create this device provider.
  *
  * Returns: (transfer none): the #GstDeviceProviderFactory used for
  *     creating this device provider. no refcounting is needed.
  *
  * Since: 1.4
  */
 GstDeviceProviderFactory *
 gst_device_provider_get_factory (GstDeviceProvider * provider)
 {
   g_return_val_if_fail (GST_IS_DEVICE_PROVIDER (provider), NULL);

   return GST_DEVICE_PROVIDER_GET_CLASS (provider)->factory;
 }

 /**
  * gst_device_provider_can_provider:
  * @provider: a #GstDeviceProvider
  *
  * If this function returns %TRUE, then the device provider can provider if
  * devices are added or removed. Otherwise, it can only do static probing.
  *
  * Returns: %TRUE if the #GstDeviceProvider support providering, %FALSE otherwise
  */
 gboolean
 gst_device_provider_can_monitor (GstDeviceProvider * provider)
 {
   GstDeviceProviderClass *klass;

   g_return_val_if_fail (GST_IS_DEVICE_PROVIDER (provider), FALSE);
   klass = GST_DEVICE_PROVIDER_GET_CLASS (provider);

   if (klass->start)
     return TRUE;
   else
     return FALSE;
 }

 /**
  * gst_device_provider_get_bus:
  * @provider: a #GstDeviceProvider
  *
  * Gets the #GstBus of this #GstDeviceProvider
  *
  * Returns: (transfer full): a #GstBus
  *
  * Since: 1.4
  */
 GstBus *
 gst_device_provider_get_bus (GstDeviceProvider * provider)
 {
   g_return_val_if_fail (GST_IS_DEVICE_PROVIDER (provider), NULL);

   return gst_object_ref (provider->priv->bus);
 }

 /**
  * gst_device_provider_device_add:
  * @provider: a #GstDeviceProvider
  * @device: (transfer full): a #GstDevice that has been added
  *
  * Posts a message on the provider's #GstBus to inform applications that
  * a new device has been added.
  *
  * This is for use by subclasses.
  *
  * Since: 1.4
  */
 void
 gst_device_provider_device_add (GstDeviceProvider * provider,
     GstDevice * device)
 {
   GstMessage *message;

   if (!gst_object_set_parent (GST_OBJECT (device), GST_OBJECT (provider))) {
     GST_WARNING_OBJECT (provider, "Could not parent device %p to provider,"
         " it already has a parent", device);
     return;
   }

   GST_OBJECT_LOCK (provider);
   provider->devices = g_list_prepend (provider->devices,
       gst_object_ref (device));
   GST_OBJECT_UNLOCK (provider);

   message = gst_message_new_device_added (GST_OBJECT (provider), device);
   gst_bus_post (provider->priv->bus, message);
   gst_object_unref (device);
 }


 /**
  * gst_device_provider_device_remove:
  * @provider: a #GstDeviceProvider
  * @device: a #GstDevice that has been removed
  *
  * Posts a message on the provider's #GstBus to inform applications that
  * a device has been removed.
  *
  * This is for use by subclasses.
  *
  * Since: 1.4
  */
 void
 gst_device_provider_device_remove (GstDeviceProvider * provider,
     GstDevice * device)
 {
   GstMessage *message;
   GList *item;

   GST_OBJECT_LOCK (provider);
   item = g_list_find (provider->devices, device);
   if (item) {
     provider->devices = g_list_delete_link (provider->devices, item);
   }
   GST_OBJECT_UNLOCK (provider);

   message = gst_message_new_device_removed (GST_OBJECT (provider), device);
   g_signal_emit_by_name (device, "removed");
   gst_bus_post (provider->priv->bus, message);
   if (item)
     gst_object_unparent (GST_OBJECT (device));
 }
	/* GStreamer
	* Copyright (C) 2012 Olivier Crete <olivier.crete@collabora.com>
	*
	* gstdeviceprovider.c: Device probing and monitoring
	*
	* This library is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Library General Public
	* License as published by the Free Software Foundation; either
	* version 2 of the License, or (at your option) any later version.
	*
	* This library 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
	* Library General Public License for more details.
	*
	* You should have received a copy of the GNU Library General Public
	* License along with this library; if not, write to the
	* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	* Boston, MA 02111-1307, USA.
	*/

	/**
	* SECTION:gstdeviceprovider
	* @short_description: A device provider
	* @see_also: #GstDevice, #GstDeviceMonitor
	*
	* A #GstDeviceProvider subclass is provided by a plugin that handles devices
	* if there is a way to programatically list connected devices. It can also
	* optionally provide updates to the list of connected devices.
	*
	* Each #GstDeviceProvider subclass is a singleton, a plugin should
	* normally provide a single subclass for all devices.
	*
	* Applications would normally use a #GstDeviceMonitor to monitor devices
	* from all relevant providers.
	*
	* Since: 1.4
	*/

	#ifdef HAVE_CONFIG_H
	#include "config.h"
	#endif

	#include "gst_private.h"

	#include "gstdeviceprovider.h"

	#include "gstelementmetadata.h"
	#include "gstquark.h"

	struct _GstDeviceProviderPrivate
	{
	GstBus *bus;

	GMutex start_lock;

	gboolean started_count;
	};

	/* this is used in gstelementfactory.c:gst_element_register() */
	GQuark __gst_deviceproviderclass_factory = 0;

	static void gst_device_provider_class_init (GstDeviceProviderClass * klass);
	static void gst_device_provider_init (GstDeviceProvider * element);
	static void gst_device_provider_base_class_init (gpointer g_class);
	static void gst_device_provider_base_class_finalize (gpointer g_class);
	static void gst_device_provider_dispose (GObject * object);
	static void gst_device_provider_finalize (GObject * object);

	static gpointer gst_device_provider_parent_class = NULL;

	GType
	gst_device_provider_get_type (void)
	{
	static volatile gsize gst_device_provider_type = 0;

	if (g_once_init_enter (&gst_device_provider_type)) {
	GType _type;
	static const GTypeInfo element_info = {
	sizeof (GstDeviceProviderClass),
	gst_device_provider_base_class_init,
	gst_device_provider_base_class_finalize,
	(GClassInitFunc) gst_device_provider_class_init,
	NULL,
	NULL,
	sizeof (GstDeviceProvider),
	0,
	(GInstanceInitFunc) gst_device_provider_init,
	NULL
	};

	_type = g_type_register_static (GST_TYPE_OBJECT, "GstDeviceProvider",
	&element_info, G_TYPE_FLAG_ABSTRACT);

	__gst_deviceproviderclass_factory =
	g_quark_from_static_string ("GST_DEVICEPROVIDERCLASS_FACTORY");
	g_once_init_leave (&gst_device_provider_type, _type);
	}
	return gst_device_provider_type;
	}

	static void
	gst_device_provider_base_class_init (gpointer g_class)
	{
	GstDeviceProviderClass *klass = GST_DEVICE_PROVIDER_CLASS (g_class);

	/* Copy the element details here so elements can inherit the
	* details from their base class and classes only need to set
	* the details in class_init instead of base_init */
	klass->metadata =
	klass->metadata ? gst_structure_copy (klass->metadata) :
	gst_structure_new_empty ("metadata");

	klass->factory = g_type_get_qdata (G_TYPE_FROM_CLASS (klass),
	__gst_deviceproviderclass_factory);
	}

	static void
	gst_device_provider_base_class_finalize (gpointer g_class)
	{
	GstDeviceProviderClass *klass = GST_DEVICE_PROVIDER_CLASS (g_class);

	gst_structure_free (klass->metadata);
	}

	static void
	gst_device_provider_class_init (GstDeviceProviderClass * klass)
	{
	GObjectClass gobject_class = (GObjectClass ) klass;

	gst_device_provider_parent_class = g_type_class_peek_parent (klass);

	g_type_class_add_private (klass, sizeof (GstDeviceProviderPrivate));

	gobject_class->dispose = gst_device_provider_dispose;
	gobject_class->finalize = gst_device_provider_finalize;
	}

	static void
	gst_device_provider_init (GstDeviceProvider * provider)
	{
	provider->priv = G_TYPE_INSTANCE_GET_PRIVATE (provider,
	GST_TYPE_DEVICE_PROVIDER, GstDeviceProviderPrivate);

	g_mutex_init (&provider->priv->start_lock);

	provider->priv->bus = gst_bus_new ();
	gst_bus_set_flushing (provider->priv->bus, TRUE);
	}


	static void
	gst_device_provider_dispose (GObject * object)
	{
	GstDeviceProvider *provider = GST_DEVICE_PROVIDER (object);

	gst_object_replace ((GstObject **) & provider->priv->bus, NULL);

	GST_OBJECT_LOCK (provider);
	g_list_free_full (provider->devices, (GDestroyNotify) gst_object_unparent);
	provider->devices = NULL;
	GST_OBJECT_UNLOCK (provider);

	G_OBJECT_CLASS (gst_device_provider_parent_class)->dispose (object);
	}

	static void
	gst_device_provider_finalize (GObject * object)
	{
	GstDeviceProvider *provider = GST_DEVICE_PROVIDER (object);

	g_mutex_clear (&provider->priv->start_lock);

	G_OBJECT_CLASS (gst_device_provider_parent_class)->finalize (object);
	}

	/**
	* gst_device_provider_class_add_metadata:
	* @klass: class to set metadata for
	* @key: the key to set
	* @value: the value to set
	*
	* Set @key with @value as metadata in @klass.
	*/
	void
	gst_device_provider_class_add_metadata (GstDeviceProviderClass * klass,
	const gchar * key, const gchar * value)
	{
	g_return_if_fail (GST_IS_DEVICE_PROVIDER_CLASS (klass));
	g_return_if_fail (key != NULL);
	g_return_if_fail (value != NULL);

	gst_structure_set ((GstStructure *) klass->metadata,
	key, G_TYPE_STRING, value, NULL);
	}

	/**
	* gst_device_provider_class_add_static_metadata:
	* @klass: class to set metadata for
	* @key: the key to set
	* @value: the value to set
	*
	* Set @key with @value as metadata in @klass.
	*
	* Same as gst_device_provider_class_add_metadata(), but @value must be a static string
	* or an inlined string, as it will not be copied. (GStreamer plugins will
	* be made resident once loaded, so this function can be used even from
	* dynamically loaded plugins.)
	*
	* Since: 1.4
	*/
	void
	gst_device_provider_class_add_static_metadata (GstDeviceProviderClass * klass,
	const gchar * key, const gchar * value)
	{
	GValue val = G_VALUE_INIT;

	g_return_if_fail (GST_IS_DEVICE_PROVIDER_CLASS (klass));
	g_return_if_fail (key != NULL);
	g_return_if_fail (value != NULL);

	g_value_init (&val, G_TYPE_STRING);
	g_value_set_static_string (&val, value);
	gst_structure_take_value ((GstStructure *) klass->metadata, key, &val);
	}

	/**
	* gst_device_provider_class_set_metadata:
	* @klass: class to set metadata for
	* @longname: The long English name of the device provider. E.g. "File Sink"
	* @classification: String describing the type of device provider, as an
	* unordered list separated with slashes ('/'). See draft-klass.txt of the
	* design docs
	* for more details and common types. E.g: "Sink/File"
	* @description: Sentence describing the purpose of the device provider.
	* E.g: "Write stream to a file"
	* @author: Name and contact details of the author(s). Use \n to separate
	* multiple author metadata. E.g: "Joe Bloggs <joe.blogs at foo.com>"
	*
	* Sets the detailed information for a #GstDeviceProviderClass.
	* <note>This function is for use in _class_init functions only.</note>
	*
	* Since: 1.4
	*/
	void
	gst_device_provider_class_set_metadata (GstDeviceProviderClass * klass,
	const gchar * longname, const gchar * classification,
	const gchar * description, const gchar * author)
	{
	g_return_if_fail (GST_IS_DEVICE_PROVIDER_CLASS (klass));
	g_return_if_fail (longname != NULL && *longname != '\0');
	g_return_if_fail (classification != NULL && *classification != '\0');
	g_return_if_fail (description != NULL && *description != '\0');
	g_return_if_fail (author != NULL && *author != '\0');

	gst_structure_id_set ((GstStructure *) klass->metadata,
	GST_QUARK (ELEMENT_METADATA_LONGNAME), G_TYPE_STRING, longname,
	GST_QUARK (ELEMENT_METADATA_KLASS), G_TYPE_STRING, classification,
	GST_QUARK (ELEMENT_METADATA_DESCRIPTION), G_TYPE_STRING, description,
	GST_QUARK (ELEMENT_METADATA_AUTHOR), G_TYPE_STRING, author, NULL);
	}

	/**
	* gst_device_provider_class_set_static_metadata:
	* @klass: class to set metadata for
	* @longname: The long English name of the element. E.g. "File Sink"
	* @classification: String describing the type of element, as an unordered list
	* separated with slashes ('/'). See draft-klass.txt of the design docs
	* for more details and common types. E.g: "Sink/File"
	* @description: Sentence describing the purpose of the element.
	* E.g: "Write stream to a file"
	* @author: Name and contact details of the author(s). Use \n to separate
	* multiple author metadata. E.g: "Joe Bloggs <joe.blogs at foo.com>"
	*
	* Sets the detailed information for a #GstDeviceProviderClass.
	* <note>This function is for use in _class_init functions only.</note>
	*
	* Same as gst_device_provider_class_set_metadata(), but @longname, @classification,
	* @description, and @author must be static strings or inlined strings, as
	* they will not be copied. (GStreamer plugins will be made resident once
	* loaded, so this function can be used even from dynamically loaded plugins.)
	*
	* Since: 1.4
	*/
	void
	gst_device_provider_class_set_static_metadata (GstDeviceProviderClass * klass,
	const gchar * longname, const gchar * classification,
	const gchar * description, const gchar * author)
	{
	GstStructure s = (GstStructure ) klass->metadata;
	GValue val = G_VALUE_INIT;

	g_return_if_fail (GST_IS_DEVICE_PROVIDER_CLASS (klass));
	g_return_if_fail (longname != NULL && *longname != '\0');
	g_return_if_fail (classification != NULL && *classification != '\0');
	g_return_if_fail (description != NULL && *description != '\0');
	g_return_if_fail (author != NULL && *author != '\0');

	g_value_init (&val, G_TYPE_STRING);

	g_value_set_static_string (&val, longname);
	gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_LONGNAME), &val);

	g_value_set_static_string (&val, classification);
	gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_KLASS), &val);

	g_value_set_static_string (&val, description);
	gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_DESCRIPTION),
	&val);

	g_value_set_static_string (&val, author);
	gst_structure_id_take_value (s, GST_QUARK (ELEMENT_METADATA_AUTHOR), &val);
	}

	/**
	* gst_device_provider_class_get_metadata:
	* @klass: class to get metadata for
	* @key: the key to get
	*
	* Get metadata with @key in @klass.
	*
	* Returns: the metadata for @key.
	*
	* Since: 1.4
	*/
	const gchar *
	gst_device_provider_class_get_metadata (GstDeviceProviderClass * klass,
	const gchar * key)
	{
	g_return_val_if_fail (GST_IS_DEVICE_PROVIDER_CLASS (klass), NULL);
	g_return_val_if_fail (key != NULL, NULL);

	return gst_structure_get_string ((GstStructure *) klass->metadata, key);
	}

	/**
	* gst_device_provider_get_devices:
	* @provider: A #GstDeviceProvider
	*
	* Gets a list of devices that this provider understands. This may actually
	* probe the hardware if the provider is not currently started.
	*
	* Returns: (transfer full) (element-type GstDevice): a #GList of
	* #GstDevice
	*
	* Since: 1.4
	*/

	GList *
	gst_device_provider_get_devices (GstDeviceProvider * provider)
	{
	GstDeviceProviderClass *klass;
	GList *devices = NULL;
	gboolean started;
	GList *item;

	g_return_val_if_fail (GST_IS_DEVICE_PROVIDER (provider), NULL);
	klass = GST_DEVICE_PROVIDER_GET_CLASS (provider);

	g_mutex_lock (&provider->priv->start_lock);
	started = (provider->priv->started_count > 0);

	if (started) {
	GST_OBJECT_LOCK (provider);
	for (item = provider->devices; item; item = item->next)
	devices = g_list_prepend (devices, gst_object_ref (item->data));
	GST_OBJECT_UNLOCK (provider);
	} else if (klass->probe)
	devices = klass->probe (provider);

	g_mutex_unlock (&provider->priv->start_lock);

	return devices;
	}

	/**
	* gst_device_provider_start:
	* @provider: A #GstDeviceProvider
	*
	* Starts providering the devices. This will cause #GST_MESSAGE_DEVICE messages
	* to be posted on the provider's bus when devices are added or removed from
	* the system.
	*
	* Since the #GstDeviceProvider is a singleton,
	* gst_device_provider_start() may already have been called by another
	* user of the object, gst_device_provider_stop() needs to be called the same
	* number of times.
	*
	* Returns: %TRUE if the device providering could be started
	*
	* Since: 1.4
	*/

	gboolean
	gst_device_provider_start (GstDeviceProvider * provider)
	{
	GstDeviceProviderClass *klass;
	gboolean ret = FALSE;

	g_return_val_if_fail (GST_IS_DEVICE_PROVIDER (provider), FALSE);
	klass = GST_DEVICE_PROVIDER_GET_CLASS (provider);

	g_mutex_lock (&provider->priv->start_lock);

	if (provider->priv->started_count > 0) {
	ret = TRUE;
	goto started;
	}

	if (klass->start)
	ret = klass->start (provider);

	if (ret) {
	provider->priv->started_count++;
	gst_bus_set_flushing (provider->priv->bus, FALSE);
	}

	started:

	g_mutex_unlock (&provider->priv->start_lock);

	return ret;
	}

	/**
	* gst_device_provider_stop:
	* @provider: A #GstDeviceProvider
	*
	* Decreases the use-count by one. If the use count reaches zero, this
	* #GstDeviceProvider will stop providering the devices. This needs to be
	* called the same number of times that gst_device_provider_start() was called.
	*
	* Since: 1.4
	*/

	void
	gst_device_provider_stop (GstDeviceProvider * provider)
	{
	GstDeviceProviderClass *klass;

	g_return_if_fail (GST_IS_DEVICE_PROVIDER (provider));
	klass = GST_DEVICE_PROVIDER_GET_CLASS (provider);

	g_mutex_lock (&provider->priv->start_lock);

	if (provider->priv->started_count == 1) {
	gst_bus_set_flushing (provider->priv->bus, TRUE);
	if (klass->stop)
	klass->stop (provider);
	GST_OBJECT_LOCK (provider);
	g_list_free_full (provider->devices, (GDestroyNotify) gst_object_unparent);
	provider->devices = NULL;
	GST_OBJECT_UNLOCK (provider);
	} else if (provider->priv->started_count < 1) {
	g_critical
	("Trying to stop a GstDeviceProvider %s which is already stopped",
	GST_OBJECT_NAME (provider));
	}

	provider->priv->started_count--;
	g_mutex_unlock (&provider->priv->start_lock);
	}


	/**
	* gst_device_provider_get_factory:
	* @provider: a #GstDeviceProvider to request the device provider factory of.
	*
	* Retrieves the factory that was used to create this device provider.
	*
	* Returns: (transfer none): the #GstDeviceProviderFactory used for
	* creating this device provider. no refcounting is needed.
	*
	* Since: 1.4
	*/
	GstDeviceProviderFactory *
	gst_device_provider_get_factory (GstDeviceProvider * provider)
	{
	g_return_val_if_fail (GST_IS_DEVICE_PROVIDER (provider), NULL);

	return GST_DEVICE_PROVIDER_GET_CLASS (provider)->factory;
	}

	/**
	* gst_device_provider_can_provider:
	* @provider: a #GstDeviceProvider
	*
	* If this function returns %TRUE, then the device provider can provider if
	* devices are added or removed. Otherwise, it can only do static probing.
	*
	* Returns: %TRUE if the #GstDeviceProvider support providering, %FALSE otherwise
	*/
	gboolean
	gst_device_provider_can_monitor (GstDeviceProvider * provider)
	{
	GstDeviceProviderClass *klass;

	g_return_val_if_fail (GST_IS_DEVICE_PROVIDER (provider), FALSE);
	klass = GST_DEVICE_PROVIDER_GET_CLASS (provider);

	if (klass->start)
	return TRUE;
	else
	return FALSE;
	}

	/**
	* gst_device_provider_get_bus:
	* @provider: a #GstDeviceProvider
	*
	* Gets the #GstBus of this #GstDeviceProvider
	*
	* Returns: (transfer full): a #GstBus
	*
	* Since: 1.4
	*/
	GstBus *
	gst_device_provider_get_bus (GstDeviceProvider * provider)
	{
	g_return_val_if_fail (GST_IS_DEVICE_PROVIDER (provider), NULL);

	return gst_object_ref (provider->priv->bus);
	}

	/**
	* gst_device_provider_device_add:
	* @provider: a #GstDeviceProvider
	* @device: (transfer full): a #GstDevice that has been added
	*
	* Posts a message on the provider's #GstBus to inform applications that
	* a new device has been added.
	*
	* This is for use by subclasses.
	*
	* Since: 1.4
	*/
	void
	gst_device_provider_device_add (GstDeviceProvider * provider,
	GstDevice * device)
	{
	GstMessage *message;

	if (!gst_object_set_parent (GST_OBJECT (device), GST_OBJECT (provider))) {
	GST_WARNING_OBJECT (provider, "Could not parent device %p to provider,"
	" it already has a parent", device);
	return;
	}

	GST_OBJECT_LOCK (provider);
	provider->devices = g_list_prepend (provider->devices,
	gst_object_ref (device));
	GST_OBJECT_UNLOCK (provider);

	message = gst_message_new_device_added (GST_OBJECT (provider), device);
	gst_bus_post (provider->priv->bus, message);
	gst_object_unref (device);
	}


	/**
	* gst_device_provider_device_remove:
	* @provider: a #GstDeviceProvider
	* @device: a #GstDevice that has been removed
	*
	* Posts a message on the provider's #GstBus to inform applications that
	* a device has been removed.
	*
	* This is for use by subclasses.
	*
	* Since: 1.4
	*/
	void
	gst_device_provider_device_remove (GstDeviceProvider * provider,
	GstDevice * device)
	{
	GstMessage *message;
	GList *item;

	GST_OBJECT_LOCK (provider);
	item = g_list_find (provider->devices, device);
	if (item) {
	provider->devices = g_list_delete_link (provider->devices, item);
	}
	GST_OBJECT_UNLOCK (provider);

	message = gst_message_new_device_removed (GST_OBJECT (provider), device);
	g_signal_emit_by_name (device, "removed");
	gst_bus_post (provider->priv->bus, message);
	if (item)
	gst_object_unparent (GST_OBJECT (device));
	}