Em 20-08-2010 12:29, Laurent Pinchart escreveu:
> As video hardware pipelines become increasingly complex and
> configurable, the current hardware description through v4l2 subdevices
> reaches its limits. In addition to enumerating and configuring
> subdevices, video camera drivers need a way to discover and modify at
> runtime how those subdevices are connected. This is done through new
> elements called entities, pads and links.
>
> 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.
>
> Links are stored in the source entity. To make backwards graph walk
> faster, a copy of all links is also stored in the sink entity. The copy
> is known as a backlink and is only used to help graph traversal.
>
> The entity API is made of three functions:
>
> - media_entity_init() initializes an entity. The caller must provide an
> array of pads as well as an estimated number of links. The links array
> is allocated dynamically and will be reallocated if it grows beyond the
> initial estimate.
>
> - media_entity_cleanup() frees resources allocated for an entity. It
> must be called during the cleanup phase after unregistering the entity
> and before freeing it.
>
> - media_entity_create_link() creates a link between two entities. An
> entry in the link array of each entity is allocated and stores pointers
> to source and sink pads.
>
> When a media device is unregistered, all its entities are unregistered
> automatically.
>
> The code is based on Hans Verkuil <hverk...@xs4all.nl> initial work.
>
> Signed-off-by: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
> Signed-off-by: Sakari Ailus <sakari.ai...@maxwell.research.nokia.com>
> ---
> Documentation/media-framework.txt | 149
> +++++++++++++++++++++++++++++++++++++
> drivers/media/Makefile | 2 +-
> drivers/media/media-device.c | 53 +++++++++++++
> drivers/media/media-entity.c | 145 ++++++++++++++++++++++++++++++++++++
> include/media/media-device.h | 19 +++++
> include/media/media-entity.h | 96 ++++++++++++++++++++++++
> 6 files changed, 463 insertions(+), 1 deletions(-)
> create mode 100644 drivers/media/media-entity.c
> create mode 100644 include/media/media-entity.h
>
> diff --git a/Documentation/media-framework.txt
> b/Documentation/media-framework.txt
> index 89dc7ad..35d74e4 100644
> --- a/Documentation/media-framework.txt
> +++ b/Documentation/media-framework.txt
> @@ -35,6 +35,30 @@ belong to userspace.
> The media kernel API aims at solving those problems.
>
>
> +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
> +modeled 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
> ------------
>
> @@ -89,3 +113,128 @@ Drivers unregister media device instances by calling
>
> Unregistering a media device that hasn't been registered is *NOT* safe.
>
> +
> +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 entities by calling
> +
> + media_entity_init(struct media_entity *entity, u16 num_pads,
> + struct media_pad *pads, u16 extra_links);
> +
> +The media_entity name, type, flags, revision and group_id fields can be
> +initialized before or after calling media_entity_init. Entities embedded in
> +higher-level standard structures can have some of those fields set by the
> +higher-level framework.
> +
> +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_init. The function will initialize the other pads fields.
> +
> +Unlike the number of pads, the total number of links isn't always known in
> +advance by the entity driver. As an initial estimate, media_entity_init
> +pre-allocates a number of links equal to the number of pads plus an optional
> +number of extra links. The links array will be reallocated if it grows beyond
> +the initial estimate.
> +
> +Drivers register entities with a media device by calling
> +
> + media_device_register_entity(struct media_device *mdev,
> + struct media_entity *entity);
> +
> +When registered the entity is assigned an ID. Entity IDs are positive
> integers
> +and are guaranteed to be unique in the context of the media device. The
> +framework doesn't guarantee that IDs will always be continuous.
> +
> +Drivers unregister entities by calling
> +
> + media_device_unregister_entity(struct media_entity *entity);
> +
> +Unregistering an entity will not change the IDs of the other entities, and
> the
> +ID will never be reused for a newly registered entity.
> +
> +When a media device is unregistered, all its entities are unregistered
> +automatically. No manual entities unregistration is then required.
> +
> +Drivers free resources associated with an entity by calling
> +
> + media_entity_cleanup(struct media_entity *entity);
> +
> +This function must be called during the cleanup phase after unregistering the
> +entity. Note that the media_entity instance itself must be freed explicitly
> by
> +the driver if required.
> +
> +Entities have flags that describe the entity capabilities and state.
> +
> + MEDIA_ENTITY_FLAG_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.
> +
> +Logical entity groups can be defined by setting the group ID of all member
> +entities to the same non-zero value. An entity group serves no purpose in the
> +kernel, but is reported to userspace during entities enumeration. The
> group_id
> +field belongs to the media device driver and must not by touched by entity
> +drivers.
> +
> +Media device drivers should define groups if several entities are logically
> +bound together. Example usages include reporting
> +
> + - ALSA, VBI and video nodes that carry the same media stream
> + - lens and flash controllers associated with a sensor
> +
> +- 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_FLAG_INPUT indicates that the pad supports sinking data.
> + MEDIA_PAD_FLAG_OUTPUT indicates that the pad supports sourcing data.
> +
> +One and only one of MEDIA_PAD_FLAG_INPUT and MEDIA_PAD_FLAG_OUTPUT must be
> set
> +for each pad.
> +
> +- Links
> +
> +Links are represented by a struct media_link instance, defined in
> +include/media/media-entity.h. Each entity stores all links originating at or
> +targetting any of its pads in a links array. A given link is thus stored
> +twice, once in the source entity and once in the target entity. The array is
> +pre-allocated and grows dynamically as needed.
> +
> +Drivers create links by calling
> +
> + media_entity_create_link(struct media_entity *source, u16 source_pad,
> + struct media_entity *sink, u16 sink_pad,
> + u32 flags);
> +
> +An entry in the link array of each entity is allocated and stores pointers
> +to source and sink pads.
> +
> +Links have flags that describe the link capabilities and state.
> +
> + MEDIA_LINK_FLAG_ACTIVE indicates that the link is active and can be
> + used to transfer media data. When two or more links target a sink pad,
> + only one of them can be active at a time.
> + MEDIA_LINK_FLAG_IMMUTABLE indicates that the link active state can't
> + be modified at runtime. If MEDIA_LINK_FLAG_IMMUTABLE is set, then
> + MEDIA_LINK_FLAG_ACTIVE must also be set since an immutable link is
> + always active.
> +
> diff --git a/drivers/media/Makefile b/drivers/media/Makefile
> index f8d8dcb..a425581 100644
> --- a/drivers/media/Makefile
> +++ b/drivers/media/Makefile
> @@ -2,7 +2,7 @@
> # Makefile for the kernel multimedia device drivers.
> #
>
> -media-objs := media-device.o media-devnode.o
> +media-objs := media-device.o media-devnode.o media-entity.o
>
> obj-$(CONFIG_MEDIA_SUPPORT) += media.o
>
> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> index 781c641..eeb002e 100644
> --- a/drivers/media/media-device.c
> +++ b/drivers/media/media-device.c
> @@ -23,6 +23,7 @@
>
> #include <media/media-device.h>
> #include <media/media-devnode.h>
> +#include <media/media-entity.h>
>
> static const struct media_file_operations media_device_fops = {
> .owner = THIS_MODULE,
> @@ -67,6 +68,10 @@ int __must_check media_device_register(struct media_device
> *mdev)
> if (WARN_ON(mdev->dev == NULL || mdev->model[0] == 0))
> return 0;
>
> + mdev->entity_id = 1;
> + INIT_LIST_HEAD(&mdev->entities);
> + spin_lock_init(&mdev->lock);
> +
> /* Register the device node. */
> mdev->devnode.fops = &media_device_fops;
> mdev->devnode.parent = mdev->dev;
> @@ -92,7 +97,55 @@ EXPORT_SYMBOL_GPL(media_device_register);
> */
> void media_device_unregister(struct media_device *mdev)
> {
> + struct media_entity *entity;
> + struct media_entity *next;
> +
> + list_for_each_entry_safe(entity, next, &mdev->entities, list)
> + media_device_unregister_entity(entity);
> +
> device_remove_file(&mdev->devnode.dev, &dev_attr_model);
> media_devnode_unregister(&mdev->devnode);
> }
> EXPORT_SYMBOL_GPL(media_device_unregister);
> +
> +/**
> + * media_device_register_entity - Register an entity with a media device
> + * @mdev: The media device
> + * @entity: The entity
> + */
> +int __must_check media_device_register_entity(struct media_device *mdev,
> + struct media_entity *entity)
> +{
> + /* Warn if we apparently re-register an entity */
> + WARN_ON(entity->parent != NULL);
Instead, it should just return -EINVAL and use __must_check.
What's the sense of allowing registering it twice?
> + entity->parent = mdev;
> +
> + spin_lock(&mdev->lock);
> + entity->id = mdev->entity_id++;
> + list_add_tail(&entity->list, &mdev->entities);
> + spin_unlock(&mdev->lock);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(media_device_register_entity);
> +
> +/**
> + * media_device_unregister_entity - Unregister an entity
> + * @entity: The entity
> + *
> + * If the entity has never been registered this function will return
> + * immediately.
> + */
> +void media_device_unregister_entity(struct media_entity *entity)
> +{
> + struct media_device *mdev = entity->parent;
> +
> + if (mdev == NULL)
> + return;
> +
> + spin_lock(&mdev->lock);
> + list_del(&entity->list);
> + spin_unlock(&mdev->lock);
> + entity->parent = NULL;
> +}
> +EXPORT_SYMBOL_GPL(media_device_unregister_entity);
> diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
> new file mode 100644
> index 0000000..541063b
> --- /dev/null
> +++ b/drivers/media/media-entity.c
> @@ -0,0 +1,145 @@
> +/*
> + * Media Entity support
> + *
> + * Copyright (C) 2010 Laurent Pinchart <laurent.pinch...@ideasonboard.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * 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
> + */
> +
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <media/media-entity.h>
> +
> +/**
> + * media_entity_init - Initialize a media entity
> + *
> + * @num_pads: Total number of input and output pads.
> + * @extra_links: Initial estimate of the number of extra links.
> + * @pads: Array of 'num_pads' pads.
> + *
> + * The total number of pads is an intrinsic property of entities known by the
> + * entity driver, while the total number of links depends on hardware design
> + * and is an extrinsic property unknown to the entity driver. However, in
> most
> + * use cases the entity driver can guess the number of links which can safely
> + * be assumed to be equal to or larger than the number of pads.
> + *
> + * For those reasons the links array can be preallocated based on the entity
> + * driver guess and will be reallocated later if extra links need to be
> + * created.
> + *
> + * This function allocates a links array with enough space to hold at least
> + * 'num_pads' + 'extra_links' elements. The media_entity::max_links field
> will
> + * be set to the number of allocated elements.
> + *
> + * The pads array is managed by the entity driver and passed to
> + * media_entity_init() where its pointer will be stored in the entity
> structure.
> + */
> +int
> +media_entity_init(struct media_entity *entity, u16 num_pads,
> + struct media_pad *pads, u16 extra_links)
> +{
> + struct media_link *links;
> + unsigned int max_links = num_pads + extra_links;
> + unsigned int i;
> +
> + links = kzalloc(max_links * sizeof(links[0]), GFP_KERNEL);
> + if (links == NULL)
> + return -ENOMEM;
> +
> + entity->group_id = 0;
> + entity->max_links = max_links;
> + entity->num_links = 0;
> + entity->num_backlinks = 0;
> + entity->num_pads = num_pads;
> + entity->pads = pads;
> + entity->links = links;
> +
> + for (i = 0; i < num_pads; i++) {
> + pads[i].entity = entity;
> + pads[i].index = i;
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(media_entity_init);
Just use EXPORT_SYMBOL_GPL() for all symbols that needs to be exported.
> +
> +void
> +media_entity_cleanup(struct media_entity *entity)
> +{
> + kfree(entity->links);
> +}
> +EXPORT_SYMBOL(media_entity_cleanup);
> +
> +static struct media_link *media_entity_add_link(struct media_entity *entity)
> +{
> + if (entity->num_links >= entity->max_links) {
> + struct media_link *links = entity->links;
> + unsigned int max_links = entity->max_links + 2;
> + unsigned int i;
> +
> + links = krealloc(links, max_links * sizeof(*links), GFP_KERNEL);
> + if (links == NULL)
> + return NULL;
> +
> + for (i = 0; i < entity->num_links; i++)
> + links[i].reverse->reverse = &links[i];
> +
> + entity->max_links = max_links;
> + entity->links = links;
> + }
> +
> + return &entity->links[entity->num_links++];
> +}
> +
> +int
> +media_entity_create_link(struct media_entity *source, u16 source_pad,
> + struct media_entity *sink, u16 sink_pad, u32 flags)
> +{
> + struct media_link *link;
> + struct media_link *backlink;
> +
> + BUG_ON(source == NULL || sink == NULL);
> + BUG_ON(source_pad >= source->num_pads);
> + BUG_ON(sink_pad >= sink->num_pads);
> +
> + link = media_entity_add_link(source);
> + if (link == NULL)
> + return -ENOMEM;
> +
> + link->source = &source->pads[source_pad];
> + link->sink = &sink->pads[sink_pad];
> + link->flags = flags;
> +
> + /* Create the backlink. Backlinks are used to help graph traversal and
> + * are not reported to userspace.
> + */
> + backlink = media_entity_add_link(sink);
> + if (backlink == NULL) {
> + source->num_links--;
> + return -ENOMEM;
> + }
> +
> + backlink->source = &source->pads[source_pad];
> + backlink->sink = &sink->pads[sink_pad];
> + backlink->flags = flags;
> +
> + link->reverse = backlink;
> + backlink->reverse = link;
> +
> + sink->num_backlinks++;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(media_entity_create_link);
> diff --git a/include/media/media-device.h b/include/media/media-device.h
> index 4fe949e..7e2dac2 100644
> --- a/include/media/media-device.h
> +++ b/include/media/media-device.h
> @@ -23,8 +23,10 @@
>
> #include <linux/device.h>
> #include <linux/list.h>
> +#include <linux/spinlock.h>
>
> #include <media/media-devnode.h>
> +#include <media/media-entity.h>
>
> /**
> * struct media_device - Media device
> @@ -35,6 +37,9 @@
> * @bus_info: Unique and stable device location identifier
> * @device_version: Hardware device version
> * @driver_version: Device driver version
> + * @entity_id: ID of the next entity to be registered
> + * @entities: List of registered entities
> + * @lock: Entities list lock
> *
> * This structure represents an abstract high-level media device. It allows
> easy
> * access to entities and provides basic media device-level support. The
> @@ -56,9 +61,23 @@ struct media_device {
> u8 bus_info[32];
> u32 device_version;
> u32 driver_version;
> +
> + u32 entity_id;
> + struct list_head entities;
> +
> + /* Protects the entities list */
> + spinlock_t lock;
> };
>
> int __must_check media_device_register(struct media_device *mdev);
> void media_device_unregister(struct media_device *mdev);
>
> +int __must_check media_device_register_entity(struct media_device *mdev,
> + struct media_entity *entity);
> +void media_device_unregister_entity(struct media_entity *entity);
> +
> +/* Iterate over all entities. */
> +#define media_device_for_each_entity(entity, mdev) \
> + list_for_each_entry(entity, &(mdev)->entities, list)
> +
> #endif
> diff --git a/include/media/media-entity.h b/include/media/media-entity.h
> new file mode 100644
> index 0000000..32bb20a
> --- /dev/null
> +++ b/include/media/media-entity.h
> @@ -0,0 +1,96 @@
> +#ifndef _MEDIA_ENTITY_H
> +#define _MEDIA_ENTITY_H
> +
> +#include <linux/list.h>
> +
> +#define MEDIA_ENTITY_TYPE_SHIFT 16
> +#define MEDIA_ENTITY_TYPE_MASK 0x00ff0000
> +#define MEDIA_ENTITY_SUBTYPE_MASK 0x0000ffff
> +
> +#define MEDIA_ENTITY_TYPE_NODE (1 <<
> MEDIA_ENTITY_TYPE_SHIFT)
> +#define MEDIA_ENTITY_TYPE_NODE_V4L (MEDIA_ENTITY_TYPE_NODE + 1)
> +#define MEDIA_ENTITY_TYPE_NODE_FB (MEDIA_ENTITY_TYPE_NODE + 2)
> +#define MEDIA_ENTITY_TYPE_NODE_ALSA (MEDIA_ENTITY_TYPE_NODE + 3)
> +#define MEDIA_ENTITY_TYPE_NODE_DVB (MEDIA_ENTITY_TYPE_NODE + 4)
> +
> +#define MEDIA_ENTITY_TYPE_SUBDEV (2 << MEDIA_ENTITY_TYPE_SHIFT)
> +#define MEDIA_ENTITY_TYPE_SUBDEV_SENSOR
> (MEDIA_ENTITY_TYPE_SUBDEV + 1)
> +#define MEDIA_ENTITY_TYPE_SUBDEV_FLASH
> (MEDIA_ENTITY_TYPE_SUBDEV + 2)
> +#define MEDIA_ENTITY_TYPE_SUBDEV_LENS
> (MEDIA_ENTITY_TYPE_SUBDEV + 3)
> +
> +#define MEDIA_ENTITY_FLAG_DEFAULT (1 << 0)
> +
> +#define MEDIA_LINK_FLAG_ACTIVE (1 << 0)
> +#define MEDIA_LINK_FLAG_IMMUTABLE (1 << 1)
> +
> +#define MEDIA_PAD_FLAG_INPUT (1 << 0)
> +#define MEDIA_PAD_FLAG_OUTPUT (1 << 1)
> +
> +struct media_link {
> + struct media_pad *source; /* Source pad */
> + struct media_pad *sink; /* Sink pad */
> + struct media_link *reverse; /* Link in the reverse direction */
> + unsigned long flags; /* Link flags (MEDIA_LINK_FLAG_*) */
> +};
> +
> +struct media_pad {
> + 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_FLAG_*) */
> +};
> +
> +struct media_entity {
> + struct list_head list;
> + struct media_device *parent; /* Media device this entity belongs to*/
> + u32 id; /* Entity ID, unique in the parent media
> + * device context */
> + const char *name; /* Entity name */
> + u32 type; /* Entity type (MEDIA_ENTITY_TYPE_*) */
> + u32 revision; /* Entity revision, driver specific */
> + unsigned long flags; /* Entity flags (MEDIA_ENTITY_FLAG_*) */
> + u32 group_id; /* Entity group ID */
> +
> + u16 num_pads; /* Number of input and output pads */
> + u16 num_links; /* Number of existing links, both active
> + * and inactive */
> + u16 num_backlinks; /* Number of backlinks */
> + u16 max_links; /* Maximum number of links */
> +
> + struct media_pad *pads; /* Pads array (num_pads elements) */
> + struct media_link *links; /* Links array (max_links elements)*/
> +
> + union {
> + /* Node specifications */
> + struct {
> + u32 major;
> + u32 minor;
> + } v4l;
> + struct {
> + u32 major;
> + u32 minor;
> + } fb;
> + int alsa;
> + int dvb;
> +
> + /* Sub-device specifications */
> + /* Nothing needed yet */
> + };
> +};
> +
> +static inline u32 media_entity_type(struct media_entity *entity)
> +{
> + return entity->type & MEDIA_ENTITY_TYPE_MASK;
> +}
> +
> +static inline u32 media_entity_subtype(struct media_entity *entity)
> +{
> + return entity->type & MEDIA_ENTITY_SUBTYPE_MASK;
> +}
> +
> +int media_entity_init(struct media_entity *entity, u16 num_pads,
> + struct media_pad *pads, u16 extra_links);
> +void media_entity_cleanup(struct media_entity *entity);
> +int media_entity_create_link(struct media_entity *source, u16 source_pad,
> + struct media_entity *sink, u16 sink_pad, u32 flags);
> +
> +#endif
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