linux-next/include/media/media-device.h

/*
 * Media device
 *
 * Copyright (C) 2010 Nokia Corporation
 *
 * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 *	     Sakari Ailus <sakari.ailus@iki.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifndef _MEDIA_DEVICE_H
#define _MEDIA_DEVICE_H

#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>

#include <media/media-devnode.h>
#include <media/media-entity.h>

/**
 * DOC: Media Controller
 *
 * The media controller userspace API is documented in DocBook format in
 * Documentation/DocBook/media/v4l/media-controller.xml. This document focus
 * on the kernel-side implementation of the media framework.
 *
 * * Abstract media device model:
 *
 * Discovering a device internal topology, and configuring it at runtime, is one
 * of the goals of the media framework. To achieve this, hardware devices are
 * modelled as an oriented graph of building blocks called entities connected
 * through pads.
 *
 * An entity is a basic media hardware building block. It can correspond to
 * a large variety of logical blocks such as physical hardware devices
 * (CMOS sensor for instance), logical hardware devices (a building block
 * in a System-on-Chip image processing pipeline), DMA channels or physical
 * connectors.
 *
 * A pad is a connection endpoint through which an entity can interact with
 * other entities. Data (not restricted to video) produced by an entity
 * flows from the entity's output to one or more entity inputs. Pads should
 * not be confused with physical pins at chip boundaries.
 *
 * A link is a point-to-point oriented connection between two pads, either
 * on the same entity or on different entities. Data flows from a source
 * pad to a sink pad.
 *
 *
 * * Media device:
 *
 * A media device is represented by a struct &media_device instance, defined in
 * include/media/media-device.h. Allocation of the structure is handled by the
 * media device driver, usually by embedding the &media_device instance in a
 * larger driver-specific structure.
 *
 * Drivers register media device instances by calling
 *	__media_device_register() via the macro media_device_register()
 * and unregistered by calling
 *	media_device_unregister().
 *
 * * Entities, pads and links:
 *
 * - Entities
 *
 * Entities are represented by a struct &media_entity instance, defined in
 * include/media/media-entity.h. The structure is usually embedded into a
 * higher-level structure, such as a v4l2_subdev or video_device instance,
 * although drivers can allocate entities directly.
 *
 * Drivers initialize entity pads by calling
 *	media_entity_pads_init().
 *
 * Drivers register entities with a media device by calling
 *	media_device_register_entity()
 * and unregistred by calling
 *	media_device_unregister_entity().
 *
 * - Interfaces
 *
 * Interfaces are represented by a struct &media_interface instance, defined in
 * include/media/media-entity.h. Currently, only one type of interface is
 * defined: a device node. Such interfaces are represented by a struct
 * &media_intf_devnode.
 *
 * Drivers initialize and create device node interfaces by calling
 *	media_devnode_create()
 * and remove them by calling:
 *	media_devnode_remove().
 *
 * - Pads
 *
 * Pads are represented by a struct &media_pad instance, defined in
 * include/media/media-entity.h. Each entity stores its pads in a pads array
 * managed by the entity driver. Drivers usually embed the array in a
 * driver-specific structure.
 *
 * Pads are identified by their entity and their 0-based index in the pads
 * array.
 * Both information are stored in the &media_pad structure, making the
 * &media_pad pointer the canonical way to store and pass link references.
 *
 * Pads have flags that describe the pad capabilities and state.
 *
 *	%MEDIA_PAD_FL_SINK indicates that the pad supports sinking data.
 *	%MEDIA_PAD_FL_SOURCE indicates that the pad supports sourcing data.
 *
 * NOTE: One and only one of %MEDIA_PAD_FL_SINK and %MEDIA_PAD_FL_SOURCE must
 * be set for each pad.
 *
 * - Links
 *
 * Links are represented by a struct &media_link instance, defined in
 * include/media/media-entity.h. There are two types of links:
 *
 * 1. pad to pad links:
 *
 * Associate two entities via their PADs. Each entity has a list that points
 * to all links originating at or targeting any of its pads.
 * A given link is thus stored twice, once in the source entity and once in
 * the target entity.
 *
 * Drivers create pad to pad links by calling:
 *	media_create_pad_link() and remove with media_entity_remove_links().
 *
 * 2. interface to entity links:
 *
 * Associate one interface to a Link.
 *
 * Drivers create interface to entity links by calling:
 *	media_create_intf_link() and remove with media_remove_intf_links().
 *
 * NOTE:
 *
 * Links can only be created after having both ends already created.
 *
 * Links have flags that describe the link capabilities and state. The
 * valid values are described at media_create_pad_link() and
 * media_create_intf_link().
 *
 * Graph traversal:
 *
 * The media framework provides APIs to iterate over entities in a graph.
 *
 * To iterate over all entities belonging to a media device, drivers can use
 * the media_device_for_each_entity macro, defined in
 * include/media/media-device.h.
 *
 * 	struct media_entity *entity;
 *
 * 	media_device_for_each_entity(entity, mdev) {
 * 		// entity will point to each entity in turn
 * 		...
 * 	}
 *
 * Drivers might also need to iterate over all entities in a graph that can be
 * reached only through enabled links starting at a given entity. The media
 * framework provides a depth-first graph traversal API for that purpose.
 *
 * Note that graphs with cycles (whether directed or undirected) are *NOT*
 * supported by the graph traversal API. To prevent infinite loops, the graph
 * traversal code limits the maximum depth to MEDIA_ENTITY_ENUM_MAX_DEPTH,
 * currently defined as 16.
 *
 * Drivers initiate a graph traversal by calling
 *	media_entity_graph_walk_start()
 *
 * The graph structure, provided by the caller, is initialized to start graph
 * traversal at the given entity.
 *
 * Drivers can then retrieve the next entity by calling
 *	media_entity_graph_walk_next()
 *
 * When the graph traversal is complete the function will return NULL.
 *
 * Graph traversal can be interrupted at any moment. No cleanup function call
 * is required and the graph structure can be freed normally.
 *
 * Helper functions can be used to find a link between two given pads, or a pad
 * connected to another pad through an enabled link
 *	media_entity_find_link() and media_entity_remote_pad()
 *
 * Use count and power handling:
 *
 * Due to the wide differences between drivers regarding power management
 * needs, the media controller does not implement power management. However,
 * the &media_entity structure includes a use_count field that media drivers
 * can use to track the number of users of every entity for power management
 * needs.
 *
 * The &media_entity.@use_count field is owned by media drivers and must not be
 * touched by entity drivers. Access to the field must be protected by the
 * &media_device.@graph_mutex lock.
 *
 * Links setup:
 *
 * Link properties can be modified at runtime by calling
 *	media_entity_setup_link()
 *
 * Pipelines and media streams:
 *
 * When starting streaming, drivers must notify all entities in the pipeline to
 * prevent link states from being modified during streaming by calling
 *	media_entity_pipeline_start().
 *
 * The function will mark all entities connected to the given entity through
 * enabled links, either directly or indirectly, as streaming.
 *
 * The &media_pipeline instance pointed to by the pipe argument will be stored
 * in every entity in the pipeline. Drivers should embed the &media_pipeline
 * structure in higher-level pipeline structures and can then access the
 * pipeline through the &media_entity pipe field.
 *
 * Calls to media_entity_pipeline_start() can be nested. The pipeline pointer
 * must be identical for all nested calls to the function.
 *
 * media_entity_pipeline_start() may return an error. In that case, it will
 * clean up any of the changes it did by itself.
 *
 * When stopping the stream, drivers must notify the entities with
 *	media_entity_pipeline_stop().
 *
 * If multiple calls to media_entity_pipeline_start() have been made the same
 * number of media_entity_pipeline_stop() calls are required to stop streaming.
 * The &media_entity pipe field is reset to NULL on the last nested stop call.
 *
 * Link configuration will fail with -%EBUSY by default if either end of the
 * link is a streaming entity. Links that can be modified while streaming must
 * be marked with the %MEDIA_LNK_FL_DYNAMIC flag.
 *
 * If other operations need to be disallowed on streaming entities (such as
 * changing entities configuration parameters) drivers can explicitly check the
 * media_entity stream_count field to find out if an entity is streaming. This
 * operation must be done with the media_device graph_mutex held.
 *
 * Link validation:
 *
 * Link validation is performed by media_entity_pipeline_start() for any
 * entity which has sink pads in the pipeline. The
 * &media_entity.@link_validate() callback is used for that purpose. In
 * @link_validate() callback, entity driver should check that the properties of
 * the source pad of the connected entity and its own sink pad match. It is up
 * to the type of the entity (and in the end, the properties of the hardware)
 * what matching actually means.
 *
 * Subsystems should facilitate link validation by providing subsystem specific
 * helper functions to provide easy access for commonly needed information, and
 * in the end provide a way to use driver-specific callbacks.
 */

struct ida;
struct device;

/**
 * struct media_device - Media device
 * @dev:	Parent device
 * @devnode:	Media device node
 * @model:	Device model name
 * @serial:	Device serial number (optional)
 * @bus_info:	Unique and stable device location identifier
 * @hw_revision: Hardware device revision
 * @driver_version: Device driver version
 * @topology_version: Monotonic counter for storing the version of the graph
 *		topology. Should be incremented each time the topology changes.
 * @id:		Unique ID used on the last registered graph object
 * @entity_internal_idx: Unique internal entity ID used by the graph traversal
 *		algorithms
 * @entity_internal_idx_max: Allocated internal entity indices
 * @entities:	List of registered entities
 * @interfaces:	List of registered interfaces
 * @pads:	List of registered pads
 * @links:	List of registered links
 * @lock:	Entities list lock
 * @graph_mutex: Entities graph operation lock
 * @link_notify: Link state change notification callback
 *
 * This structure represents an abstract high-level media device. It allows easy
 * access to entities and provides basic media device-level support. The
 * structure can be allocated directly or embedded in a larger structure.
 *
 * The parent @dev is a physical device. It must be set before registering the
 * media device.
 *
 * @model is a descriptive model name exported through sysfs. It doesn't have to
 * be unique.
 */
struct media_device {
	/* dev->driver_data points to this struct. */
	struct device *dev;
	struct media_devnode devnode;

	char model[32];
	char serial[40];
	char bus_info[32];
	u32 hw_revision;
	u32 driver_version;

	u32 topology_version;

	u32 id;
	struct ida entity_internal_idx;
	int entity_internal_idx_max;

	struct list_head entities;
	struct list_head interfaces;
	struct list_head pads;
	struct list_head links;

	/* Protects the graph objects creation/removal */
	spinlock_t lock;
	/* Serializes graph operations. */
	struct mutex graph_mutex;

	int (*link_notify)(struct media_link *link, u32 flags,
			   unsigned int notification);
};

#ifdef CONFIG_MEDIA_CONTROLLER

/* Supported link_notify @notification values. */
#define MEDIA_DEV_NOTIFY_PRE_LINK_CH	0
#define MEDIA_DEV_NOTIFY_POST_LINK_CH	1

/* media_devnode to media_device */
#define to_media_device(node) container_of(node, struct media_device, devnode)

/**
 * media_entity_enum_init - Initialise an entity enumeration
 *
 * @ent_enum: Entity enumeration to be initialised
 * @mdev: The related media device
 *
 * Returns zero on success or a negative error code.
 */
static inline __must_check int media_entity_enum_init(
	struct media_entity_enum *ent_enum, struct media_device *mdev)
{
	return __media_entity_enum_init(ent_enum,
					mdev->entity_internal_idx_max + 1);
}

/**
 * media_device_init() - Initializes a media device element
 *
 * @mdev:	pointer to struct &media_device
 *
 * This function initializes the media device prior to its registration.
 * The media device initialization and registration is split in two functions
 * to avoid race conditions and make the media device available to user-space
 * before the media graph has been completed.
 *
 * So drivers need to first initialize the media device, register any entity
 * within the media device, create pad to pad links and then finally register
 * the media device by calling media_device_register() as a final step.
 */
void media_device_init(struct media_device *mdev);

/**
 * media_device_cleanup() - Cleanups a media device element
 *
 * @mdev:	pointer to struct &media_device
 *
 * This function that will destroy the graph_mutex that is
 * initialized in media_device_init().
 */
void media_device_cleanup(struct media_device *mdev);

/**
 * __media_device_register() - Registers a media device element
 *
 * @mdev:	pointer to struct &media_device
 * @owner:	should be filled with %THIS_MODULE
 *
 * Users, should, instead, call the media_device_register() macro.
 *
 * The caller is responsible for initializing the media_device structure before
 * registration. The following fields must be set:
 *
 *  - dev must point to the parent device (usually a &pci_dev, &usb_interface or
 *    &platform_device instance).
 *
 *  - model must be filled with the device model name as a NUL-terminated UTF-8
 *    string. The device/model revision must not be stored in this field.
 *
 * The following fields are optional:
 *
 *  - serial is a unique serial number stored as a NUL-terminated ASCII string.
 *    The field is big enough to store a GUID in text form. If the hardware
 *    doesn't provide a unique serial number this field must be left empty.
 *
 *  - bus_info represents the location of the device in the system as a
 *    NUL-terminated ASCII string. For PCI/PCIe devices bus_info must be set to
 *    "PCI:" (or "PCIe:") followed by the value of pci_name(). For USB devices,
 *    the usb_make_path() function must be used. This field is used by
 *    applications to distinguish between otherwise identical devices that don't
 *    provide a serial number.
 *
 *  - hw_revision is the hardware device revision in a driver-specific format.
 *    When possible the revision should be formatted with the KERNEL_VERSION
 *    macro.
 *
 *  - driver_version is formatted with the KERNEL_VERSION macro. The version
 *    minor must be incremented when new features are added to the userspace API
 *    without breaking binary compatibility. The version major must be
 *    incremented when binary compatibility is broken.
 *
 * Notes:
 *
 * Upon successful registration a character device named media[0-9]+ is created.
 * The device major and minor numbers are dynamic. The model name is exported as
 * a sysfs attribute.
 *
 * Unregistering a media device that hasn't been registered is *NOT* safe.
 *
 * Return: returns zero on success or a negative error code.
 */
int __must_check __media_device_register(struct media_device *mdev,
					 struct module *owner);
#define media_device_register(mdev) __media_device_register(mdev, THIS_MODULE)

/**
 * __media_device_unregister() - Unegisters a media device element
 *
 * @mdev:	pointer to struct &media_device
 *
 *
 * It is safe to call this function on an unregistered (but initialised)
 * media device.
 */
void media_device_unregister(struct media_device *mdev);

/**
 * media_device_register_entity() - registers a media entity inside a
 *	previously registered media device.
 *
 * @mdev:	pointer to struct &media_device
 * @entity:	pointer to struct &media_entity to be registered
 *
 * Entities are identified by a unique positive integer ID. The media
 * controller framework will such ID automatically. IDs are not guaranteed
 * to be contiguous, and the ID number can change on newer Kernel versions.
 * So, neither the driver nor userspace should hardcode ID numbers to refer
 * to the entities, but, instead, use the framework to find the ID, when
 * needed.
 *
 * The media_entity name, type and flags fields should be initialized before
 * calling media_device_register_entity(). Entities embedded in higher-level
 * standard structures can have some of those fields set by the higher-level
 * framework.
 *
 * If the device has pads, media_entity_pads_init() should be called before
 * this function. Otherwise, the &media_entity.@pad and &media_entity.@num_pads
 * should be zeroed before calling this function.
 *
 * Entities have flags that describe the entity capabilities and state:
 *
 * %MEDIA_ENT_FL_DEFAULT indicates the default entity for a given type.
 *	This can be used to report the default audio and video devices or the
 *	default camera sensor.
 *
 * NOTE: Drivers should set the entity function before calling this function.
 * Please notice that the values %MEDIA_ENT_F_V4L2_SUBDEV_UNKNOWN and
 * %MEDIA_ENT_F_UNKNOWN should not be used by the drivers.
 */
int __must_check media_device_register_entity(struct media_device *mdev,
					      struct media_entity *entity);

/*
 * media_device_unregister_entity() - unregisters a media entity.
 *
 * @entity:	pointer to struct &media_entity to be unregistered
 *
 * All links associated with the entity and all PADs are automatically
 * unregistered from the media_device when this function is called.
 *
 * Unregistering an entity will not change the IDs of the other entities and
 * the previoully used ID will never be reused for a newly registered entities.
 *
 * When a media device is unregistered, all its entities are unregistered
 * automatically. No manual entities unregistration is then required.
 *
 * Note: the media_entity instance itself must be freed explicitly by
 * the driver if required.
 */
void media_device_unregister_entity(struct media_entity *entity);

/**
 * media_device_get_devres() -	get media device as device resource
 *				creates if one doesn't exist
 *
 * @dev: pointer to struct &device.
 *
 * Sometimes, the media controller &media_device needs to be shared by more
 * than one driver. This function adds support for that, by dynamically
 * allocating the &media_device and allowing it to be obtained from the
 * struct &device associated with the common device where all sub-device
 * components belong. So, for example, on an USB device with multiple
 * interfaces, each interface may be handled by a separate per-interface
 * drivers. While each interface have its own &device, they all share a
 * common &device associated with the hole USB device.
 */
struct media_device *media_device_get_devres(struct device *dev);

/**
 * media_device_find_devres() - find media device as device resource
 *
 * @dev: pointer to struct &device.
 */
struct media_device *media_device_find_devres(struct device *dev);

/* Iterate over all entities. */
#define media_device_for_each_entity(entity, mdev)			\
	list_for_each_entry(entity, &(mdev)->entities, graph_obj.list)

/* Iterate over all interfaces. */
#define media_device_for_each_intf(intf, mdev)			\
	list_for_each_entry(intf, &(mdev)->interfaces, graph_obj.list)

/* Iterate over all pads. */
#define media_device_for_each_pad(pad, mdev)			\
	list_for_each_entry(pad, &(mdev)->pads, graph_obj.list)

/* Iterate over all links. */
#define media_device_for_each_link(link, mdev)			\
	list_for_each_entry(link, &(mdev)->links, graph_obj.list)
#else
static inline int media_device_register(struct media_device *mdev)
{
	return 0;
}
static inline void media_device_unregister(struct media_device *mdev)
{
}
static inline int media_device_register_entity(struct media_device *mdev,
						struct media_entity *entity)
{
	return 0;
}
static inline void media_device_unregister_entity(struct media_entity *entity)
{
}
static inline struct media_device *media_device_get_devres(struct device *dev)
{
	return NULL;
}
static inline struct media_device *media_device_find_devres(struct device *dev)
{
	return NULL;
}
#endif /* CONFIG_MEDIA_CONTROLLER */
#endif