/*dev->driver_data points to this struct*/

struct media_device { //媒体设备结构体

    struct device *dev; //Parent device

    struct media_devnode devnode; //媒体设备节点

    char model[];//设备型号名称

    char driver_name[]; //驱动的名称,如果没有设置，就返回dev->driver->name

    char serial[];//设备序列号

    char bus_info[];//设备位置标识符

    u32 hw_revision;

    u32 driver_version; //驱动版本

    u32 topology_version; //拓扑版本

    u32 id;//注册的图形对象上使用的唯一ID

    struct ida entity_internal_idx;

    int entity_internal_idx_max;

    struct list_head entities; //List of registered entities

    struct list_head interfaces; //List of registered interfaces

    struct list_head pads; //List of registered pads

    struct list_head links; //List of registered links
　　 /*entity注册成功的回调通知链表*/

    struct list_head entity_notify; //notify callback list invoked when a new entity is registered

    spinlock_t lock; //Protects the graph objects creation/removal

    struct mutex graph_mutex; //Serializes graph operations.

    struct media_entity_graph pm_count_walk; //Graph walk for power state walk.

    void *source_priv;//Driver Private data for enable/disable source handlers

    int (*enable_source)(struct media_entity *entity, struct media_pipeline *pipe);

    void (*disable_source)(struct media_entity *entity);
　　/**
　　* Supported link_notify @notification values.
　　　　#define MEDIA_DEV_NOTIFY_PRE_LINK_CH	0
　　　　#define MEDIA_DEV_NOTIFY_POST_LINK_CH	1
　　*/
　　int (*link_notify)(struct media_link *link, u32 flags, unsigned int notification);//Link state change notification callback

};

/*此结构体对应于struct media_device结构体中的 struct list_head entity_notify链表*/

struct media_entity_notify {

    struct list_head list;

    void *notify_data; // Input data to invoke the callback

    void (*notify)(struct media_entity *entity, void *notify_data); //Callback function pointer

};