[media] media-entity.h: document all the structs

Only a few structs are documented on kernel-doc-nano format
(the ones added by the MC next gen patches).

Add a documentation for all structs, and ensure that they'll
be producing the documentation at the Kernel's device driver
DocBook.
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

include/media/media-entity.h

@@ -55,11 +55,13 @@ enum media_gobj_type {
 /**
  * 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_LOCAL_ID	to store a per-type ID
  *		(called as "local 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
  */
@@ -73,6 +75,28 @@ struct media_gobj {
 struct media_pipeline {
 };
 
+/**
+ * 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.
+ * @source:	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_*)
+ */
 struct media_link {
 	struct media_gobj graph_obj;
 	struct list_head list;
@@ -86,15 +110,23 @@ struct media_link {
 		struct media_pad *sink;
 		struct media_entity *entity;
 	};
-	struct media_link *reverse;	/* Link in the reverse direction */
-	unsigned long flags;		/* Link flags (MEDIA_LNK_FL_*) */
+	struct media_link *reverse;
+	unsigned long flags;
 };
 
+/**
+ * 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
+ * @flags:	Pad flags, as defined in uapi/media.h (MEDIA_PAD_FL_*)
+ */
 struct media_pad {
 	struct media_gobj graph_obj;	/* must be first field in struct */
-	struct media_entity *entity;	/* Entity this pad belongs to */
-	u16 index;			/* Pad index in the entity pads array */
-	unsigned long flags;		/* Pad flags (MEDIA_PAD_FL_*) */
+	struct media_entity *entity;
+	u16 index;
+	unsigned long flags;
 };
 
 /**
@@ -113,56 +145,78 @@ struct media_entity_operations {
 	int (*link_validate)(struct media_link *link);
 };
 
+/**
+ * struct media_entity - A media entity graph object.
+ *
+ * @graph_obj:	Embedded structure containing the media object common data.
+ * @name:	Entity name.
+ * @type:	Entity type, as defined in uapi/media.h (MEDIA_ENT_T_*)
+ * @revision:	Entity revision - OBSOLETE - should be removed soon.
+ * @flags:	Entity flags, as defined in uapi/media.h (MEDIA_ENT_FL_*)
+ * @group_id:	Entity group ID - OBSOLETE - should be removed soon.
+ * @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
+ * @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.
+ * @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;		/* Entity name */
-	u32 type;			/* Entity type (MEDIA_ENT_T_*) */
-	u32 revision;			/* Entity revision, driver specific */
-	unsigned long flags;		/* Entity flags (MEDIA_ENT_FL_*) */
-	u32 group_id;			/* Entity group ID */
+	const char *name;
+	u32 type;
+	u32 revision;
+	unsigned long flags;
+	u32 group_id;
 
-	u16 num_pads;			/* Number of sink and source pads */
-	u16 num_links;			/* Number of existing links, both
-					 * enabled and disabled */
-	u16 num_backlinks;		/* Number of backlinks */
+	u16 num_pads;
+	u16 num_links;
+	u16 num_backlinks;
 
-	struct media_pad *pads;		/* Pads array (num_pads objects) */
-	struct list_head links;		/* Pad-to-pad links list */
+	struct media_pad *pads;
+	struct list_head links;
 
-	const struct media_entity_operations *ops;	/* Entity operations */
+	const struct media_entity_operations *ops;
 
 	/* 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.
 	 */
-	int stream_count;		/* Stream count for the entity. */
-	int use_count;			/* Use count for the entity. */
+	int stream_count;
+	int use_count;
 
-	struct media_pipeline *pipe;	/* Pipeline this entity belongs to. */
+	struct media_pipeline *pipe;
 
 	union {
-		/* Node specifications */
 		struct {
 			u32 major;
 			u32 minor;
 		} dev;
-
-		/* Sub-device specifications */
-		/* Nothing needed yet */
 	} info;
 };
 
 /**
- * struct media_intf_devnode - Define a Kernel API interface
+ * struct media_interface - A media interface graph object.
  *
  * @graph_obj:		embedded graph object
- * @list:		Linked list used to find other interfaces that belong
- *			to the same media controller
  * @links:		List of links pointing to graph entities
- * @type:		Type of the interface as defined at the
+ * @type:		Type of the interface as defined in the
  *			uapi/media/media.h header, e. g.
  *			MEDIA_INTF_T_*
- * @flags:		Interface flags as defined at uapi/media/media.h
+ * @flags:		Interface flags as defined in uapi/media/media.h
  */
 struct media_interface {
 	struct media_gobj		graph_obj;
@@ -172,7 +226,7 @@ struct media_interface {
 };
 
 /**
- * struct media_intf_devnode - Define a Kernel API interface via a device node
+ * struct media_intf_devnode - A media interface via a device node.
  *
  * @intf:	embedded interface object
  * @major:	Major number of a device node