text: /* SPDX-License-Identifier: GPL-2.0-only */
  /*
   * Media entity
   *
   * Copyright (C) 2010 Nokia Corporation
   *
   * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
   *	     Sakari Ailus <sakari.ailus@iki.fi>
   */
  
  #ifndef _MEDIA_ENTITY_H
  #define _MEDIA_ENTITY_H
  
  #include <linux/bitmap.h>
  #include <linux/bug.h>
  #include <linux/fwnode.h>
  #include <linux/kernel.h>
  #include <linux/list.h>
  #include <linux/media.h>
  
  /* Enums used internally at the media controller to represent graphs */
  
  /**
   * enum media_gobj_type - type of a graph object
   *
   * @MEDIA_GRAPH_ENTITY:		Identify a media entity
   * @MEDIA_GRAPH_PAD:		Identify a media pad
   * @MEDIA_GRAPH_LINK:		Identify a media link
   * @MEDIA_GRAPH_INTF_DEVNODE:	Identify a media Kernel API interface via
   *				a device node
   */
  enum media_gobj_type {
  	MEDIA_GRAPH_ENTITY,
  	MEDIA_GRAPH_PAD,
  	MEDIA_GRAPH_LINK,
  	MEDIA_GRAPH_INTF_DEVNODE,
  };
  
  #define MEDIA_BITS_PER_TYPE		8
  #define MEDIA_BITS_PER_ID		(32 - MEDIA_BITS_PER_TYPE)
  #define MEDIA_ID_MASK			 GENMASK_ULL(MEDIA_BITS_PER_ID - 1, 0)
  
  /* Structs to represent the objects that belong to a media graph */
  
  /**
   * struct media_gobj - Define a graph object.
   *
   * @mdev:	Pointer to the struct &media_device that owns the object
   * @id:		Non-zero object ID identifier. The ID should be unique
   *		inside a media_device, as it is composed by
   *		%MEDIA_BITS_PER_TYPE to store the type plus
   *		%MEDIA_BITS_PER_ID to store the ID
   * @list:	List entry stored in one of the per-type mdev object lists
   *
   * All objects on the media graph should have this struct embedded
   */
  struct media_gobj {
  	struct media_device	*mdev;
  	u32			id;
  	struct list_head	list;
  };
  
  #define MEDIA_ENTITY_ENUM_MAX_DEPTH	16
  
  /**
   * struct media_entity_enum - An enumeration of media entities.
   *
   * @bmap:	Bit map in which each bit represents one entity at struct
   *		media_entity->internal_idx.
   * @idx_max:	Number of bits in bmap
   */
  struct media_entity_enum {
  	unsigned long *bmap;
  	int idx_max;
  };
  
  /**
   * struct media_graph - Media graph traversal state
   *
   * @stack:		Graph traversal stack; the stack contains information
   *			on the path the media entities to be walked and the
   *			links through which they were reached.
   * @stack.entity:	pointer to &struct media_entity at the graph.
   * @stack.link:		pointer to &struct list_head.
   * @ent_enum:		Visited entities
   * @top:		The top of the stack
   */
  struct media_graph {
  	struct {
  		struct media_entity *entity;
  		struct list_head *link;
  	} stack[MEDIA_ENTITY_ENUM_MAX_DEPTH];
  
  	struct media_entity_enum ent_enum;
  	int top;
  };
  
  /**
   * struct media_pipeline - Media pipeline related information
   *
   * @streaming_count:	Streaming start count - streaming stop count
   * @graph:		Media graph walk during pipeline start / stop
   */
  struct media_pipeline {
  	int streaming_count;
  	struct media_graph graph;
  };
  
  /**
   * struct media_link - A link object part of a media graph.
   *
   * @graph_obj:	Embedded structure containing the media object common data
   * @list:	Linked list associated with an entity or an interface that
   *		owns the link.
   * @gobj0:	Part of a union. Used to get the pointer for the first
   *		graph_object of the link.
   * @source:	Part of a union. Used only if the first object (gobj0) is
   *		a pad. In that case, it represents the source pad.
   * @intf:	Part of a union. Used only if the first object (gobj0) is
   *		an interface.
   * @gobj1:	Part of a union. Used to get the pointer for the second
   *		graph_object of the link.
   * @sink:	Part of a union. Used only if the second object (gobj1) is
   *		a pad. In that case, it represents the sink pad.
   * @entity:	Part of a union. Used only if the second object (gobj1) is
   *		an entity.
   * @reverse:	Pointer to the link for the reverse direction of a pad to pad
   *		link.
   * @flags:	Link flags, as defined in uapi/media.h (MEDIA_LNK_FL_*)
   * @is_backlink: Indicate if the link is a backlink.
   */
  struct media_link {
  	struct media_gobj graph_obj;
  	struct list_head list;
  	union {
  		struct media_gobj *gobj0;
  		struct media_pad *source;
  		struct media_interface *intf;
  	};
  	union {
  		struct media_gobj *gobj1;
  		struct media_pad *sink;
  		struct media_entity *entity;
  	};
  	struct media_link *reverse;
  	unsigned long flags;
  	bool is_backlink;
  };
  
  /**
   * enum media_pad_signal_type - type of the signal inside a media pad
   *
   * @PAD_SIGNAL_DEFAULT:
   *	Default signal. Use this when all inputs or all outputs are
   *	uniquely identified by the pad number.
   * @PAD_SIGNAL_ANALOG:
   *	The pad contains an analog signal. It can be Radio Frequency,
   *	Intermediate Frequency, a baseband signal or sub-cariers.
   *	Tuner inputs, IF-PLL demodulators, composite and s-video signals
   *	should use it.
   * @PAD_SIGNAL_DV:
   *	Contains a digital video signal, with can be a bitstream of samples
   *	taken from an analog TV video source. On such case, it usually
   *	contains the VBI data on it.
   * @PAD_SIGNAL_AUDIO:
   *	Contains an Intermediate Frequency analog signal from an audio
   *	sub-carrier or an audio bitstream. IF signals are provided by tuners
   *	and consumed by	audio AM/FM decoders. Bitstream audio is provided by
   *	an audio decoder.
   */
  enum media_pad_signal_type {
  	PAD_SIGNAL_DEFAULT = 0,
  	PAD_SIGNAL_ANALOG,
  	PAD_SIGNAL_DV,
  	PAD_SIGNAL_AUDIO,
  };
  
  /**
   * struct media_pad - A media pad graph object.
   *
   * @graph_obj:	Embedded structure containing the media object common data
   * @entity:	Entity this pad belongs to
   * @index:	Pad index in the entity pads array, numbered from 0 to n
   * @sig_type:	Type of the signal inside a media pad
   * @flags:	Pad flags, as defined in
   *		:ref:`include/uapi/linux/media.h <media_header>`
   *		(seek for ``MEDIA_PAD_FL_*``)
   */
  struct media_pad {
  	struct media_gobj graph_obj;	/* must be first field in struct */
  	struct media_entity *entity;
  	u16 index;
  	enum media_pad_signal_type sig_type;
  	unsigned long flags;
  };
  
  /**
   * struct media_entity_operations - Media entity operations
   * @get_fwnode_pad:	Return the pad number based on a fwnode endpoint or
   *			a negative value on error. This operation can be used
   *			to map a fwnode to a media pad number. Optional.
   * @link_setup:		Notify the entity of link changes. The operation can
   *			return an error, in which case link setup will be
   *			cancelled. Optional.
   * @link_validate:	Return whether a link is valid from the entity point of
   *			view. The media_pipeline_start() function
   *			validates all links by calling this operation. Optional.
   *
   * .. note::
   *
   *    Those these callbacks are called with struct &media_device.graph_mutex
   *    mutex held.
   */
  struct media_entity_operations {
  	int (*get_fwnode_pad)(struct media_entity *entity,
  			      struct fwnode_endpoint *endpoint);
  	int (*link_setup)(struct media_entity *entity,
  			  const struct media_pad *local,
  			  const struct media_pad *remote, u32 flags);
  	int (*link_validate)(struct media_link *link);
  };
  
  /**
   * enum media_entity_type - Media entity type
   *
   * @MEDIA_ENTITY_TYPE_BASE:
   *	The entity isn't embedded in another subsystem structure.
   * @MEDIA_ENTITY_TYPE_VIDEO_DEVICE:
   *	The entity is embedded in a struct video_device instance.
   * @MEDIA_ENTITY_TYPE_V4L2_SUBDEV:
   *	The entity is embedded in a struct v4l2_subdev instance.
   *
   * Media entity objects are often not instantiated directly, but the media
   * entity structure is inherited by (through embedding) other subsystem-specific
   * structures. The media entity type identifies the type of the subclass
   * structure that implements a media entity instance.
   *
   * This allows runtime type identification of media entities and safe casting to
   * the correct object type. For instance, a media entity structure instance
   * embedded in a v4l2_subdev structure instance will have the type
   * %MEDIA_ENTITY_TYPE_V4L2_SUBDEV and can safely be cast to a &v4l2_subdev
   * structure using the container_of() macro.
   */
  enum media_entity_type {
  	MEDIA_ENTITY_TYPE_BASE,
  	MEDIA_ENTITY_TYPE_VIDEO_DEVICE,
  	MEDIA_ENTITY_TYPE_V4L2_SUBDEV,
  };
  
  /**
   * struct media_entity - A media entity graph object.
   *
   * @graph_obj:	Embedded structure containing the media object common data.
   * @name:	Entity name.
   * @obj_type:	Type of the object that implements the media_entity.
   * @function:	Entity main function, as defined in
   *		:ref:`include/uapi/linux/media.h <media_header>`
   *		(seek for ``MEDIA_ENT_F_*``)
   * @flags:	Entity flags, as defined in
   *		:ref:`include/uapi/linux/media.h <media_header>`
   *		(seek for ``MEDIA_ENT_FL_*``)
   * @num_pads:	Number of sink and source pads.
   * @num_links:	Total number of links, forward and back, enabled and disabled.
   * @num_backlinks: Number of backlinks
   * @internal_idx: An unique internal entity specific number. The numbers are
   *		re-used if entities are unregistered or registered again.
   * @pads:	Pads array with the size defined by @num_pads.
   * @links:	List of data links.
   * @ops:	Entity operations.
   * @stream_count: Stream count for the entity.
   * @use_count:	Use count for the entity.
   * @pipe:	Pipeline this entity belongs to.
   * @info:	Union with devnode information.  Kept just for backward
   *		compatibility.
   * @info.dev:	Contains device major and minor info.
   * @info.dev.major: device node major, if the device is a devnode.
   * @info.dev.minor: device node minor, if the device is a devnode.
   * @major:	Devnode major number (zero if not applicable). Kept just
   *		for backward compatibility.
   * @minor:	Devnode minor number (zero if not applicable). Kept just
   *		for backward compatibility.
   *
   * .. note::
   *
   *    @stream_count and @use_count reference counts must never be
   *    negative, but are signed integers on purpose: a simple ``WARN_ON(<0)``
   *    check can be used to detect reference count bugs that would make them
   *    negative.
   */
  struct media_entity {
  	struct media_gobj graph_obj;	/* must be first field in struct */
  	const char *name;
  	enum media_entity_type obj_type;
  	u32 function;
  	unsigned long flags;
  
  	u16 num_pads;
  	u16 num_links;
  	u16 num_backlinks;
  	int internal_idx;
  
  	struct media_pad *pads;
  	struct list_head links;
  
  	const struct media_entity_operations *ops;
  
  	int stream_count;
  	int use_count;
  
  	struct media_pipeline *pipe;
  
  	union {
  		struct {
  			u32 major;
  			u32 minor;
  		} dev;
  	} info;
  };
  
  /**
   * struct media_interface - A media interface graph object.
   *
   * @graph_obj:		embedded graph object
   * @links:		List of links pointing to graph entities
   * @type:		Type of the interface as defined in
   *			:ref:`include/uapi/linux/media.h <media_header>`
   *			(seek for ``MEDIA_INTF_T_*``)
   * @flags:		Interface flags as defined in
   *			:ref:`include/uapi/linux/media.h <media_header>`
   *			(seek for ``MEDIA_INTF_FL_*``)
   *
   * .. note::
   *
   *    Currently, no flags for &media_interface is defined.
   */
  struct media_interface {
  	struct media_gobj		graph_obj;
  	struct list_head		links;
  	u32				type;
  	u32				flags;
  };
  
  /**
   * struct media_intf_devnode - A media interface via a device node.
   *
   * @intf:	embedded interface object
   * @major:	Major number of a device node
   * @minor:	Minor number of a device node
   */
  struct media_intf_devnode {
  	struct media_interface		intf;
  
  	/* Should match the fields at media_v2_intf_devnode */
  	u32				major;
  	u32				minor;
  };
  
  /**
   * media_entity_id() - return the media entity graph object id
   *
   * @entity:	pointer to &media_entity
   */
  static inline u32 media_entity_id(struct media_entity *entity)
  {
  	return entity->graph_obj.id;
  }
  
  /**
   * media_type() - return the media object type
   *
   * @gobj:	Pointer to the struct &media_gobj graph object
   */
  static inline enum media_gobj_type media_type(struct media_gobj *gobj)
  {
  	return gobj->id >> MEDIA_BITS_PER_ID;
  }
  
  /**
   * media_id() - return the media object ID
   *
   * @gobj:	Pointer to the struct &media_gobj graph object
   */
  static inline u32 media_id(struct media_gobj *gobj)
  {
  	return gobj->id & MEDIA_ID_MASK;
  }
  
  /**
   * media_gobj_gen_id() - encapsulates type and ID on at the object ID
   *
   * @type:	object type as define at enum &media_gobj_type.
   * @local_id:	next ID, from struct &media_device.id.
   */
  static inline u32 media_gobj_gen_id(enum media_gobj_type type, u64 local_id)
  {
  	u32 id;
  
  	id = type << MEDIA_BITS_PER_ID;
  	id |= local_id & MEDIA_ID_MASK;
  
  	return id;
  }
  
  /**
   * is_media_entity_v4l2_video_device() - Check if the entity is a video_device
   * @entity:	pointer to entity
   *
   * Return: %true if the entity is an instance of a video_device object and can
   * safely be cast to a struct video_device using the container_of() macro, or
   * %false otherwise.
   */
  static inline bool is_media_entity_v4l2_video_device(struct media_entity *entity)
  {
  	return entity && entity->obj_type == MEDIA_ENTITY_TYPE_VIDEO_DEVICE;
  }
  
  /**
   * is_media_entity_v4l2_subdev() - Check if the entity is a v4l2_subdev
   * @entity:	pointer to entity
   *
   * Return: %true if the entity is an instance of a &v4l2_subdev object and can
   * safely be cast to a struct &v4l2_subdev using the container_of() macro, or
   * %false otherwise.
   */
  static inline bool is_media_entity_v4l2_subdev(struct media_entity *entity)
  {
  	return entity && entity->obj_type == MEDIA_ENTITY_TYPE_V4L2_SUBDEV;
  }
  
  /**
   * __media_entity_enum_init - Initialise an entity enumeration
   *
   * @ent_enum: Entity enumeration to be initialised
   * @idx_max: Maximum number of entities in the enumeration
   *
   * Return: Returns zero on success or a negative error code.
   */
  __must_check int __media_entity_enum_init(struct media_entity_enum *ent_enum,
  					  int idx_max);
  
  /**
   * media_entity_enum_cleanup - Release resources of an entity enumeration
   *
   * @ent_enum: Entity enumeration to be released
   */
  void media_entity_enum_cleanup(struct media_entity_enum *ent_enum);
  
  /**
   * media_entity_enum_zero - Clear the entire enum
   *
   * @ent_enum: Entity enumeration to be cleared
   */
  static inline void media_entity_enum_zero(struct media_entity_enum *ent_enum)
  {
  	bitmap_zero(ent_enum->bmap, ent_enum->idx_max);
  }
  
  /**
   * media_entity_enum_set - Mark a single entity in the enum
   *
   * @ent_enum: Entity enumeration
   * @entity: Entity to be marked
   */
  static inline void media_entity_enum_set(struct media_entity_enum *ent_enum,
  					 struct media_entity *entity)
  {
  	if (WARN_ON(entity->internal_idx >= ent_enum->idx_max))
  		return;
  
  	__set_bit(entity->internal_idx, ent_enum->bmap);
  }
  
  /**
   * media_entity_enum_clear - Unmark a single entity in the enum
   *
   * @ent_enum: Entity enumeration
   * @entity: Entity to be unmarked
   */
  static inline void media_entity_enum_clear(struct media_entity_enum *ent_enum,
  					   struct media_entity *entity)
  {
  	if (WARN_ON(entity->internal_idx >= ent_enum->idx_max))
  		return;
  
  	__clear_bit(entity->internal_idx, ent_enum->bmap);
  }
  
  /**
   * media_entity_enum_test - Test whether the entity is marked
   *
   * @ent_enum: Entity enumeration
   * @entity: Entity to be tested
   *
   * Returns %true if the entity was marked.
   */
  static inline bool media_entity_enum_test(struct media_entity_enum *ent_enum,
  					  struct media_entity *entity)
  {
  	if (WARN_ON(entity->internal_idx >= ent_enum->idx_max))
  		return true;
  
  	return test_bit(entity->internal_idx, ent_enum->bmap);
  }
  
  /**
   * media_entity_enum_test_and_set - Test whether the entity is marked,
   *	and mark it
   *
   * @ent_enum: Entity enumeration
   * @entity: Entity to be tested
   *
   * Returns %true if the entity was marked, and mark it before doing so.
   */
  static inline bool
  media_entity_enum_test_and_set(struct media_entity_enum *ent_enum,
  			       struct media_entity *entity)
  {
  	if (WARN_ON(entity->internal_idx >= ent_enum->idx_max))
  		return true;
  
  	return __test_and_set_bit(entity->internal_idx, ent_enum->bmap);
  }
  
  /**
   * media_entity_enum_empty - Test whether the entire enum is empty
   *
   * @ent_enum: Entity enumeration
   *
   * Return: %true if the entity was empty.
   */
  static inline bool media_entity_enum_empty(struct media_entity_enum *ent_enum)
  {
  	return bitmap_empty(ent_enum->bmap, ent_enum->idx_max);
  }
  
  /**
   * media_entity_enum_intersects - Test whether two enums intersect
   *
   * @ent_enum1: First entity enumeration
   * @ent_enum2: Second entity enumeration
   *
   * Return: %true if entity enumerations @ent_enum1 and @ent_enum2 intersect,
   * otherwise %false.
   */
  static inline bool media_entity_enum_intersects(
  	struct media_entity_enum *ent_enum1,
  	struct media_entity_enum *ent_enum2)
  {
  	WARN_ON(ent_enum1->idx_max != ent_enum2->idx_max);
  
  	return bitmap_intersects(ent_enum1->bmap, ent_enum2->bmap,
  				 min(ent_enum1->idx_max, ent_enum2->idx_max));
  }
  
  /**
   * gobj_to_entity - returns the struct &media_entity pointer from the
   *	@gobj contained on it.
   *
   * @gobj: Pointer to the struct &media_gobj graph object
   */
  #define gobj_to_entity(gobj) \
  		container_of(gobj, struct media_entity, graph_obj)
  
  /**
   * gobj_to_pad - returns the struct &media_pad pointer from the
   *	@gobj contained on it.
   *
   * @gobj: Pointer to the struct &media_gobj graph object
   */
  #define gobj_to_pad(gobj) \
  		container_of(gobj, struct media_pad, graph_obj)
  
  /**
   * gobj_to_link - returns the struct &media_link pointer from the
   *	@gobj contained on it.
   *
   * @gobj: Pointer to the struct &media_gobj graph object
   */
  #define gobj_to_link(gobj) \
  		container_of(gobj, struct media_link, graph_obj)
  
  /**
   * gobj_to_intf - returns the struct &media_interface pointer from the
   *	@gobj contained on it.
   *
   * @gobj: Pointer to the struct &media_gobj graph object
   */
  #define gobj_to_intf(gobj) \
  		container_of(gobj, struct media_interface, graph_obj)
  
  /**
   * intf_to_devnode - returns the struct media_intf_devnode pointer from the
   *	@intf contained on it.
   *
   * @intf: Pointer to struct &media_intf_devnode
   */
  #define intf_to_devnode(intf) \
  		container_of(intf, struct media_intf_devnode, intf)
  
  /**
   *  media_gobj_create - Initialize a graph object
   *
   * @mdev:	Pointer to the &media_device that contains the object
   * @type:	Type of the object
   * @gobj:	Pointer to the struct &media_gobj graph object
   *
   * This routine initializes the embedded struct &media_gobj inside a
   * media graph object. It is called automatically if ``media_*_create``
   * function calls are used. However, if the object (entity, link, pad,
   * interface) is embedded on some other object, this function should be
   * called before registering the object at the media controller.
   */
  void media_gobj_create(struct media_device *mdev,
  		    enum media_gobj_type type,
  		    struct media_gobj *gobj);
  
  /**
   *  media_gobj_destroy - Stop using a graph object on a media device
   *
   * @gobj:	Pointer to the struct &media_gobj graph object
   *
   * This should be called by all routines like media_device_unregister()
   * that remove/destroy media graph objects.
   */
  void media_gobj_destroy(struct media_gobj *gobj);
  
  /**
   * media_entity_pads_init() - Initialize the entity pads
   *
   * @entity:	entity where the pads belong
   * @num_pads:	total number of sink and source pads
   * @pads:	Array of @num_pads pads.
   *
   * The pads array is managed by the entity driver and passed to
   * media_entity_pads_init() where its pointer will be stored in the
   * &media_entity structure.
   *
   * If no pads are needed, drivers could either directly fill
   * &media_entity->num_pads with 0 and &media_entity->pads with %NULL or call
   * this function that will do the same.
   *
   * As the number of pads is known in advance, the pads array is not allocated
   * dynamically but is managed by the entity driver. Most drivers will embed the
   * pads array in a driver-specific structure, avoiding dynamic allocation.
   *
   * Drivers must set the direction of every pad in the pads array before calling
   * media_entity_pads_init(). The function will initialize the other pads fields.
   */
  int media_entity_pads_init(struct media_entity *entity, u16 num_pads,
  		      struct media_pad *pads);
  
  /**
   * media_entity_cleanup() - free resources associated with an entity
   *
   * @entity:	entity where the pads belong
   *
   * This function must be called during the cleanup phase after unregistering
   * the entity (currently, it does nothing).
   */
  #if IS_ENABLED(CONFIG_MEDIA_CONTROLLER)
  static inline void media_entity_cleanup(struct media_entity *entity) {}
  #else
  #define media_entity_cleanup(entity) do { } while (false)
  #endif
  
  /**
   * media_get_pad_index() - retrieves a pad index from an entity
   *
   * @entity:	entity where the pads belong
   * @is_sink:	true if the pad is a sink, false if it is a source
   * @sig_type:	type of signal of the pad to be search
   *
   * This helper function finds the first pad index inside an entity that
   * satisfies both @is_sink and @sig_type conditions.
   *
   * Return:
   *
   * On success, return the pad number. If the pad was not found or the media
   * entity is a NULL pointer, return -EINVAL.
   */
  int media_get_pad_index(struct media_entity *entity, bool is_sink,
  			enum media_pad_signal_type sig_type);
  
  /**
   * media_create_pad_link() - creates a link between two entities.
   *
   * @source:	pointer to &media_entity of the source pad.
   * @source_pad:	number of the source pad in the pads array
   * @sink:	pointer to &media_entity of the sink pad.
   * @sink_pad:	number of the sink pad in the pads array.
   * @flags:	Link flags, as defined in
   *		:ref:`include/uapi/linux/media.h <media_header>`
   *		( seek for ``MEDIA_LNK_FL_*``)
   *
   * Valid values for flags:
   *
   * %MEDIA_LNK_FL_ENABLED
   *   Indicates that the link is enabled and can be used to transfer media data.
   *   When two or more links target a sink pad, only one of them can be
   *   enabled at a time.
   *
   * %MEDIA_LNK_FL_IMMUTABLE
   *   Indicates that the link enabled state can't be modified at runtime. If
   *   %MEDIA_LNK_FL_IMMUTABLE is set, then %MEDIA_LNK_FL_ENABLED must also be
   *   set, since an immutable link is always enabled.
   *
   * .. note::
   *
   *    Before calling this function, media_entity_pads_init() and
   *    media_device_register_entity() should be called previously for both ends.
   */
  __must_check int media_create_pad_link(struct media_entity *source,
  			u16 source_pad, struct media_entity *sink,
  			u16 sink_pad, u32 flags);
  
  /**
   * media_create_pad_links() - creates a link between two entities.
   *
   * @mdev: Pointer to the media_device that contains the object
   * @source_function: Function of the source entities. Used only if @source is
   *	NULL.
   * @source: pointer to &media_entity of the source pad. If NULL, it will use
   *	all entities that matches the @sink_function.
   * @source_pad: number of the source pad in the pads array
   * @sink_function: Function of the sink entities. Used only if @sink is NULL.
   * @sink: pointer to &media_entity of the sink pad. If NULL, it will use
   *	all entities that matches the @sink_function.
   * @sink_pad: number of the sink pad in the pads array.
   * @flags: Link flags, as defined in include/uapi/linux/media.h.
   * @allow_both_undefined: if %true, then both @source and @sink can be NULL.
   *	In such case, it will create a crossbar between all entities that
   *	matches @source_function to all entities that matches @sink_function.
   *	If %false, it will return 0 and won't create any link if both @source
   *	and @sink are NULL.
   *
   * Valid values for flags:
   *
   * A %MEDIA_LNK_FL_ENABLED flag indicates that the link is enabled and can be
   *	used to transfer media data. If multiple links are created and this
   *	flag is passed as an argument, only the first created link will have
   *	this flag.
   *
   * A %MEDIA_LNK_FL_IMMUTABLE flag indicates that the link enabled state can't
   *	be modified at runtime. If %MEDIA_LNK_FL_IMMUTABLE is set, then
   *	%MEDIA_LNK_FL_ENABLED must also be set since an immutable link is
   *	always enabled.
   *
   * It is common for some devices to have multiple source and/or sink entities
   * of the same type that should be linked. While media_create_pad_link()
   * creates link by link, this function is meant to allow 1:n, n:1 and even
   * cross-bar (n:n) links.
   *
   * .. note::
   *
   *    Before calling this function, media_entity_pads_init() and
   *    media_device_register_entity() should be called previously for the
   *    entities to be linked.
   */
  int media_create_pad_links(const struct media_device *mdev,
  			   const u32 source_function,
  			   struct media_entity *source,
  			   const u16 source_pad,
  			   const u32 sink_function,
  			   struct media_entity *sink,
  			   const u16 sink_pad,
  			   u32 flags,
  			   const bool allow_both_undefined);
  
  void __media_entity_remove_links(struct media_entity *entity);
  
  /**
   * media_entity_remove_links() - remove all links associated with an entity
   *
   * @entity:	pointer to &media_entity
   *
   * .. note::
   *
   *    This is called automatically when an entity is unregistered via
   *    media_device_register_entity().
   */
  void media_entity_remove_links(struct media_entity *entity);
  
  /**
   * __media_entity_setup_link - Configure a media link without locking
   * @link: The link being configured
   * @flags: Link configuration flags
   *
   * The bulk of link setup is handled by the two entities connected through the
   * link. This function notifies both entities of the link configuration change.
   *
   * If the link is immutable or if the current and new configuration are
   * identical, return immediately.
   *
   * The user is expected to hold link->source->parent->mutex. If not,
   * media_entity_setup_link() should be used instead.
   */
  int __media_entity_setup_link(struct media_link *link, u32 flags);
  
  /**
   * media_entity_setup_link() - changes the link flags properties in runtime
   *
   * @link:	pointer to &media_link
   * @flags:	the requested new link flags
   *
   * The only configurable property is the %MEDIA_LNK_FL_ENABLED link flag
   * flag to enable/disable a link. Links marked with the
   * %MEDIA_LNK_FL_IMMUTABLE link flag can not be enabled or disabled.
   *
   * When a link is enabled or disabled, the media framework calls the
   * link_setup operation for the two entities at the source and sink of the
   * link, in that order. If the second link_setup call fails, another
   * link_setup call is made on the first entity to restore the original link
   * flags.
   *
   * Media device drivers can be notified of link setup operations by setting the
   * &media_device.link_notify pointer to a callback function. If provided, the
   * notification callback will be called before enabling and after disabling
   * links.
   *
   * Entity drivers must implement the link_setup operation if any of their links
   * is non-immutable. The operation must either configure the hardware or store
   * the configuration information to be applied later.
   *
   * Link configuration must not have any side effect on other links. If an
   * enabled link at a sink pad prevents another link at the same pad from
   * being enabled, the link_setup operation must return %-EBUSY and can't
   * implicitly disable the first enabled link.
   *
   * .. note::
   *
   *    The valid values of the flags for the link is the same as described
   *    on media_create_pad_link(), for pad to pad links or the same as described
   *    on media_create_intf_link(), for interface to entity links.
   */
  int media_entity_setup_link(struct media_link *link, u32 flags);
  
  /**
   * media_entity_find_link - Find a link between two pads
   * @source: Source pad
   * @sink: Sink pad
   *
   * Return: returns a pointer to the link between the two entities. If no
   * such link exists, return %NULL.
   */
  struct media_link *media_entity_find_link(struct media_pad *source,
  		struct media_pad *sink);
  
  /**
   * media_entity_remote_pad - Find the pad at the remote end of a link
   * @pad: Pad at the local end of the link
   *
   * Search for a remote pad connected to the given pad by iterating over all
   * links originating or terminating at that pad until an enabled link is found.
   *
   * Return: returns a pointer to the pad at the remote end of the first found
   * enabled link, or %NULL if no enabled link has been found.
   */
  struct media_pad *media_entity_remote_pad(const struct media_pad *pad);
  
  /**
   * media_entity_get_fwnode_pad - Get pad number from fwnode
   *
   * @entity: The entity
   * @fwnode: Pointer to the fwnode_handle which should be used to find the pad
   * @direction_flags: Expected direction of the pad, as defined in
   *		     :ref:`include/uapi/linux/media.h <media_header>`
   *		     (seek for ``MEDIA_PAD_FL_*``)
   *
   * This function can be used to resolve the media pad number from
   * a fwnode. This is useful for devices which use more complex
   * mappings of media pads.
   *
   * If the entity does not implement the get_fwnode_pad() operation
   * then this function searches the entity for the first pad that
   * matches the @direction_flags.
   *
   * Return: returns the pad number on success or a negative error code.
   */
  int media_entity_get_fwnode_pad(struct media_entity *entity,
  				struct fwnode_handle *fwnode,
  				unsigned long direction_flags);
  
  /**
   * media_graph_walk_init - Allocate resources used by graph walk.
   *
   * @graph: Media graph structure that will be used to walk the graph
   * @mdev: Pointer to the &media_device that contains the object
   */
  __must_check int media_graph_walk_init(
  	struct media_graph *graph, struct media_device *mdev);
  
  /**
   * media_graph_walk_cleanup - Release resources used by graph walk.
   *
   * @graph: Media graph structure that will be used to walk the graph
   */
  void media_graph_walk_cleanup(struct media_graph *graph);
  
  /**
   * media_graph_walk_start - Start walking the media graph at a
   *	given entity
   *
   * @graph: Media graph structure that will be used to walk the graph
   * @entity: Starting entity
   *
   * Before using this function, media_graph_walk_init() must be
   * used to allocate resources used for walking the graph. This
   * function initializes the graph traversal structure to walk the
   * entities graph starting at the given entity. The traversal
   * structure must not be modified by the caller during graph
   * traversal. After the graph walk, the resources must be released
   * using media_graph_walk_cleanup().
   */
  void media_graph_walk_start(struct media_graph *graph,
  			    struct media_entity *entity);
  
  /**
   * media_graph_walk_next - Get the next entity in the graph
   * @graph: Media graph structure
   *
   * Perform a depth-first traversal of the given media entities graph.
   *
   * The graph structure must have been previously initialized with a call to
   * media_graph_walk_start().
   *
   * Return: returns the next entity in the graph or %NULL if the whole graph
   * have been traversed.
   */
  struct media_entity *media_graph_walk_next(struct media_graph *graph);
  
  /**
   * media_pipeline_start - Mark a pipeline as streaming
   * @entity: Starting entity
   * @pipe: Media pipeline to be assigned to all entities in the pipeline.
   *
   * Mark all entities connected to a given entity through enabled links, either
   * directly or indirectly, as streaming. The given pipeline object is assigned
   * to every entity in the pipeline and stored in the media_entity pipe field.
   *
   * Calls to this function can be nested, in which case the same number of
   * media_pipeline_stop() calls will be required to stop streaming. The
   * pipeline pointer must be identical for all nested calls to
   * media_pipeline_start().
   */
  __must_check int media_pipeline_start(struct media_entity *entity,
  				      struct media_pipeline *pipe);
  /**
   * __media_pipeline_start - Mark a pipeline as streaming
   *
   * @entity: Starting entity
   * @pipe: Media pipeline to be assigned to all entities in the pipeline.
   *
   * ..note:: This is the non-locking version of media_pipeline_start()
   */
  __must_check int __media_pipeline_start(struct media_entity *entity,
  					struct media_pipeline *pipe);
  
  /**
   * media_pipeline_stop - Mark a pipeline as not streaming
   * @entity: Starting entity
   *
   * Mark all entities connected to a given entity through enabled links, either
   * directly or indirectly, as not streaming. The media_entity pipe field is
   * reset to %NULL.
   *
   * If multiple calls to media_pipeline_start() have been made, the same
   * number of calls to this function are required to mark the pipeline as not
   * streaming.
   */
  void media_pipeline_stop(struct media_entity *entity);
  
  /**
   * __media_pipeline_stop - Mark a pipeline as not streaming
   *
   * @entity: Starting entity
   *
   * .. note:: This is the non-locking version of media_pipeline_stop()
   */
  void __media_pipeline_stop(struct media_entity *entity);
  
  /**
   * media_devnode_create() - creates and initializes a device node interface
   *
   * @mdev:	pointer to struct &media_device
   * @type:	type of the interface, as given by
   *		:ref:`include/uapi/linux/media.h <media_header>`
   *		( seek for ``MEDIA_INTF_T_*``) macros.
   * @flags:	Interface flags, as defined in
   *		:ref:`include/uapi/linux/media.h <media_header>`
   *		( seek for ``MEDIA_INTF_FL_*``)
   * @major:	Device node major number.
   * @minor:	Device node minor number.
   *
   * Return: if succeeded, returns a pointer to the newly allocated
   *	&media_intf_devnode pointer.
   *
   * .. note::
   *
   *    Currently, no flags for &media_interface is defined.
   */
  struct media_intf_devnode *
  __must_check media_devnode_create(struct media_device *mdev,
  				  u32 type, u32 flags,
  				  u32 major, u32 minor);
  /**
   * media_devnode_remove() - removes a device node interface
   *
   * @devnode:	pointer to &media_intf_devnode to be freed.
   *
   * When a device node interface is removed, all links to it are automatically
   * removed.
   */
  void media_devnode_remove(struct media_intf_devnode *devnode);
  struct media_link *
  
  /**
   * media_create_intf_link() - creates a link between an entity and an interface
   *
   * @entity:	pointer to %media_entity
   * @intf:	pointer to %media_interface
   * @flags:	Link flags, as defined in
   *		:ref:`include/uapi/linux/media.h <media_header>`
   *		( seek for ``MEDIA_LNK_FL_*``)
   *
   *
   * Valid values for flags:
   *
   * %MEDIA_LNK_FL_ENABLED
   *   Indicates that the interface is connected to the entity hardware.
   *   That's the default value for interfaces. An interface may be disabled if
   *   the hardware is busy due to the usage of some other interface that it is
   *   currently controlling the hardware.
   *
   *   A typical example is an hybrid TV device that handle only one type of
   *   stream on a given time. So, when the digital TV is streaming,
   *   the V4L2 interfaces won't be enabled, as such device is not able to
   *   also stream analog TV or radio.
   *
   * .. note::
   *
   *    Before calling this function, media_devnode_create() should be called for
   *    the interface and media_device_register_entity() should be called for the
   *    interface that will be part of the link.
   */
  __must_check media_create_intf_link(struct media_entity *entity,
  				    struct media_interface *intf,
  				    u32 flags);
  /**
   * __media_remove_intf_link() - remove a single interface link
   *
   * @link:	pointer to &media_link.
   *
   * .. note:: This is an unlocked version of media_remove_intf_link()
   */
  void __media_remove_intf_link(struct media_link *link);
  
  /**
   * media_remove_intf_link() - remove a single interface link
   *
   * @link:	pointer to &media_link.
   *
   * .. note:: Prefer to use this one, instead of __media_remove_intf_link()
   */
  void media_remove_intf_link(struct media_link *link);
  
  /**
   * __media_remove_intf_links() - remove all links associated with an interface
   *
   * @intf:	pointer to &media_interface
   *
   * .. note:: This is an unlocked version of media_remove_intf_links().
   */
  void __media_remove_intf_links(struct media_interface *intf);
  
  /**
   * media_remove_intf_links() - remove all links associated with an interface
   *
   * @intf:	pointer to &media_interface
   *
   * .. note::
   *
   *   #) This is called automatically when an entity is unregistered via
   *      media_device_register_entity() and by media_devnode_remove().
   *
   *   #) Prefer to use this one, instead of __media_remove_intf_links().
   */
  void media_remove_intf_links(struct media_interface *intf);
  
  /**
   * media_entity_call - Calls a struct media_entity_operations operation on
   *	an entity
   *
   * @entity: entity where the @operation will be called
   * @operation: type of the operation. Should be the name of a member of
   *	struct &media_entity_operations.
   *
   * This helper function will check if @operation is not %NULL. On such case,
   * it will issue a call to @operation\(@entity, @args\).
   */
  
  #define media_entity_call(entity, operation, args...)			\
  	(((entity)->ops && (entity)->ops->operation) ?			\
  	 (entity)->ops->operation((entity) , ##args) : -ENOIOCTLCMD)
  
  #endif
  