Linux V4l2 框架一

v4l2的框架图

1.Linux Media Framework（媒体框架）

1.基本概念

media framework 是嵌入到lv4l2 框架中，主要分成entity pad link三大部分，entity设备的实例

pad 用来作为entity的连接点 link 用来连接entity 下图可以直观的看到

2.media的源码

1.注册media总线

首先看media-devnode.c文件，在/sys/bus/下注册了media总线，后续相关的media设备都会注册到下面

Z:\RV1109\kernel\drivers\media\media-devnode.c
subsys_initcall(media_devnode_init);static int __init media_devnode_init(void)
{int ret;pr_info("Linux media interface: v0.10\n");ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,MEDIA_NAME);if (ret < 0) {pr_warn("unable to allocate major\n");return ret;}ret = bus_register(&media_bus_type);if (ret < 0) {unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);pr_warn("bus_register failed\n");return -EIO;}return 0;
}

2.注册media实例

注册完总线后需要把媒体设备实例化，调用注册媒体设备接口在media总线下注册

Z:\RV1109\kernel\drivers\media\media-device.c
//初始化media device下的 entity pad link  链表
void media_device_init(struct media_device *mdev)
{INIT_LIST_HEAD(&mdev->entities);INIT_LIST_HEAD(&mdev->interfaces);INIT_LIST_HEAD(&mdev->pads);INIT_LIST_HEAD(&mdev->links);INIT_LIST_HEAD(&mdev->entity_notify);mutex_init(&mdev->graph_mutex);ida_init(&mdev->entity_internal_idx);dev_dbg(mdev->dev, "Media device initialized\n");
}
//将媒体实例化注册到media总线下 实际调用media_devnode_register 注册media节点
int __must_check __media_device_register(struct media_device *mdev,struct module *owner)
{struct media_devnode *devnode;int ret;devnode = kzalloc(sizeof(*devnode), GFP_KERNEL);if (!devnode)return -ENOMEM;/* Register the device node. */mdev->devnode = devnode;devnode->fops = &media_device_fops;devnode->parent = mdev->dev;devnode->release = media_device_release;/* Set version 0 to indicate user-space that the graph is static */mdev->topology_version = 0;ret = media_devnode_register(mdev, devnode, owner);if (ret < 0) {/* devnode free is handled in media_devnode_*() */mdev->devnode = NULL;return ret;}ret = device_create_file(&devnode->dev, &dev_attr_model);if (ret < 0) {/* devnode free is handled in media_devnode_*() */mdev->devnode = NULL;media_devnode_unregister_prepare(devnode);media_devnode_unregister(devnode);return ret;}dev_dbg(mdev->dev, "Media device registered\n");return 0;
}
//注册media node节点
int __must_check media_devnode_register(struct media_device *mdev,struct media_devnode *devnode,struct module *owner)
{int minor;int ret;/* Part 1: Find a free minor number */mutex_lock(&media_devnode_lock);minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);if (minor == MEDIA_NUM_DEVICES) {mutex_unlock(&media_devnode_lock);pr_err("could not get a free minor\n");kfree(devnode);return -ENFILE;}set_bit(minor, media_devnode_nums);mutex_unlock(&media_devnode_lock);devnode->minor = minor;devnode->media_dev = mdev;/* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */devnode->dev.bus = &media_bus_type;devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor);devnode->dev.release = media_devnode_release;if (devnode->parent)devnode->dev.parent = devnode->parent;dev_set_name(&devnode->dev, "media%d", devnode->minor);device_initialize(&devnode->dev);/* Part 2: Initialize the character device */cdev_init(&devnode->cdev, &media_devnode_fops);devnode->cdev.owner = owner;/* Part 3: Add the media and char device */ret = cdev_device_add(&devnode->cdev, &devnode->dev);if (ret < 0) {pr_err("%s: cdev_device_add failed\n", __func__);goto cdev_add_error;}/* Part 4: Activate this minor. The char device can now be used. */set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);return 0;cdev_add_error:mutex_lock(&media_devnode_lock);clear_bit(devnode->minor, media_devnode_nums);devnode->media_dev = NULL;mutex_unlock(&media_devnode_lock);put_device(&devnode->dev);return ret;
}

3.初始化entity 实例相关

//pads entity links 头文件
media/media-entity.h
//entity init
int media_entity_init(struct media_entity *entity, u16 num_pads,struct media_pad *pads, u16 extra_links)
//entity pad init
int media_entity_pads_init(struct media_entity *entity, u16 num_pads,struct media_pad *pads)
{struct media_device *mdev = entity->graph_obj.mdev;unsigned int i;if (num_pads >= MEDIA_ENTITY_MAX_PADS)return -E2BIG;entity->num_pads = num_pads;entity->pads = pads;if (mdev)mutex_lock(&mdev->graph_mutex);for (i = 0; i < num_pads; i++) {pads[i].entity = entity;pads[i].index = i;if (mdev)media_gobj_create(mdev, MEDIA_GRAPH_PAD,&entity->pads[i].graph_obj);}if (mdev)mutex_unlock(&mdev->graph_mutex);return 0;
}
//控制pipeline开启
__must_check int media_pipeline_start(struct media_entity *entity,struct media_pipeline *pipe)
{struct media_device *mdev = entity->graph_obj.mdev;int ret;mutex_lock(&mdev->graph_mutex);ret = __media_pipeline_start(entity, pipe);mutex_unlock(&mdev->graph_mutex);return ret;
}
//控制pipeline 关闭
void media_pipeline_stop(struct media_entity *entity)
{struct media_device *mdev = entity->graph_obj.mdev;mutex_lock(&mdev->graph_mutex);__media_pipeline_stop(entity);mutex_unlock(&mdev->graph_mutex);
}

4.links的连接

//entity的相关连接是通过pad之间的连接
//创建pad -> pad 的连接
media_create_pad_link()
//remove link
media_entity_remove_links()
//interface to entity的连接
media_create_intf_link()
//remove
media_remove_intf_links()

2.linux V4l2 Framework

1.v4l2 device

1.V4L2 device 实例基本概念

每个设备实体都代表着一个struct v4l2_device,在linux中我们往往把这个结构嵌入到大框架中，旗下包含着设备实体

2.v4l2 设备的注册以及相关操作

//注册v4l2 device
int v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev)
{if (v4l2_dev == NULL)return -EINVAL;INIT_LIST_HEAD(&v4l2_dev->subdevs);spin_lock_init(&v4l2_dev->lock);v4l2_prio_init(&v4l2_dev->prio);kref_init(&v4l2_dev->ref);get_device(dev);v4l2_dev->dev = dev;if (dev == NULL) {/* If dev == NULL, then name must be filled in by the caller */if (WARN_ON(!v4l2_dev->name[0]))return -EINVAL;return 0;}/* Set name to driver name + device name if it is empty. */if (!v4l2_dev->name[0])snprintf(v4l2_dev->name, sizeof(v4l2_dev->name), "%s %s",dev->driver->name, dev_name(dev));if (!dev_get_drvdata(dev))dev_set_drvdata(dev, v4l2_dev);return 0;
}
//初始化v4l2 device name
int v4l2_device_set_name(struct v4l2_device *v4l2_dev, const char *basename,atomic_t *instance)
{int num = atomic_inc_return(instance) - 1;int len = strlen(basename);if (basename[len - 1] >= '0' && basename[len - 1] <= '9')snprintf(v4l2_dev->name, sizeof(v4l2_dev->name),"%s-%d", basename, num);elsesnprintf(v4l2_dev->name, sizeof(v4l2_dev->name),"%s%d", basename, num);return num;
}

2.v4l2 subdevice

相对于一个监控系统来说，v4l2 subdevice 通常是作为一个sensor来做相应的操作

1.v4l2 sudevice相关操作

//v4l2 subdevice init
void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)
{INIT_LIST_HEAD(&sd->list);BUG_ON(!ops);sd->ops = ops;sd->v4l2_dev = NULL;sd->flags = 0;sd->name[0] = '\0';sd->grp_id = 0;sd->dev_priv = NULL;sd->host_priv = NULL;
#if defined(CONFIG_MEDIA_CONTROLLER)sd->entity.name = sd->name;sd->entity.obj_type = MEDIA_ENTITY_TYPE_V4L2_SUBDEV;sd->entity.function = MEDIA_ENT_F_V4L2_SUBDEV_UNKNOWN;
#endif
}
//v4l2 subdevice通常引入media framework
//注册subdevice到v4l2 框架中
v4l2_device_register_subdev();

2.I2c subdevice 相关操作

//初始化device
v4l2_i2c_subdev_init()
//v4l2_subdev struct to the i2c_client struct
struct i2c_client *client = v4l2_get_subdevdata(sd);
//i2c_client to a v4l2_subdev struct
struct v4l2_subdev *sd = i2c_get_clientdata(client);

work
//注册subdevice到v4l2 框架中
v4l2_device_register_subdev();


#### 2.I2c subdevice 相关操作```c
//初始化device
v4l2_i2c_subdev_init()
//v4l2_subdev struct to the i2c_client struct
struct i2c_client *client = v4l2_get_subdevdata(sd);
//i2c_client to a v4l2_subdev struct
struct v4l2_subdev *sd = i2c_get_clientdata(client);

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Linux 媒体框架（Media Framework）一

Linux V4l2 框架一

v4l2的框架图

1.Linux Media Framework（媒体框架）

1.基本概念

2.media的源码

1.注册media总线

2.注册media实例

3.初始化entity 实例相关

4.links的连接

2.linux V4l2 Framework

1.v4l2 device

1.V4L2 device 实例基本概念

2.v4l2 设备的注册以及相关操作

2.v4l2 subdevice

1.v4l2 sudevice相关操作

2.I2c subdevice 相关操作

Linux 媒体框架（Media Framework）一相关推荐

最新文章

热门文章

Linux 媒体框架（Media Framework）一

Linux V4l2 框架 一

v4l2的框架图

1.Linux Media Framework（ 媒体框架）

1.基本概念

2.media的源码

1.注册media总线

2.注册media实例

3.初始化entity 实例相关

4.links的连接

2.linux V4l2 Framework

1.v4l2 device

1.V4L2 device 实例基本概念

2.v4l2 设备的注册以及相关操作

2.v4l2 subdevice

1.v4l2 sudevice相关操作

2.I2c subdevice 相关操作

Linux 媒体框架（Media Framework）一相关推荐

最新文章

热门文章

Linux V4l2 框架一

1.Linux Media Framework（媒体框架）