uORBMain.cpp学习
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uorb_main
int
uorb_main(int argc, char *argv[])
{
if (argc < 2) {
usage(); //使用说明
return -EINVAL;
}
/*
* Start/load the driver. //开始或加载驱动
*/
if (!strcmp(argv[1], "start")) {
if (g_dev != nullptr) { //判断是否已经启动
PX4_WARN("already loaded");
/* user wanted to start uorb, its already running, no error */
return 0;
}
if (!uORB::Manager::initialize()) { //初始化uORB::Manager
PX4_ERR("uorb manager alloc failed");
return -ENOMEM;
}
/* create the driver */ //创建一个驱动设备
g_dev = uORB::Manager::get_instance()->get_device_master(uORB::PUBSUB);
if (g_dev == nullptr) {
return -errno;
}
#if !defined(__PX4_QURT) && !defined(__PX4_POSIX_EAGLE) && !defined(__PX4_POSIX_EXCELSIOR)
/* FIXME: this fails on Snapdragon (see https://github.com/PX4/Firmware/issues/5406),
* so we disable logging messages to the ulog for now. This needs further investigations.
*/
px4_log_initialize();
#endif
return OK;
}
/*
* Print driver information. //打印设备信息status
*/
if (!strcmp(argv[1], "status")) {
if (g_dev != nullptr) {
g_dev->printStatistics(true);
} else {
PX4_INFO("uorb is not running");
}
return OK;
}
//topming'li
if (!strcmp(argv[1], "top")) {
if (g_dev != nullptr) {
g_dev->showTop(argv + 2, argc - 2);
} else {
PX4_INFO("uorb is not running");
}
return OK;
}
usage();
return -EINVAL;
}
uORB::Manager::initialize():
bool uORB::Manager::initialize()
{
if (_Instance == nullptr) {
_Instance = new uORB::Manager(); //创建了一个新的uORB实例
}
return _Instance != nullptr;
}
uORB::Manager:
/**
* This is implemented as a singleton. This class manages creating the //这是一个实施的单例，这个class管理创建uORB节点给每个uORB topics
* uORB nodes for each uORB topics and also implements the behavor of the //并且也实施uORB的API行为
* uORB Api's.
*/
class uORB::Manager : public uORBCommunicator::IChannelRxHandler
{
public:
// public interfaces for this class. //公共的类接口
/** //初始化单例，调用这个在所有事情之前
* Initialize the singleton. Call this before everything else.
* @return true on success //返回true是成功
*/
static bool initialize();
/** //获取instance的方法
* Method to get the singleton instance for the uORB::Manager.
* Make sure initialize() is called first. //确保initialize()先被调用
* @return uORB::Manager* //返回创建的uORB：：Manager*
*/
static uORB::Manager *get_instance()
{
return _Instance;
}
/**
* Get the DeviceMaster for a given Flavor. If it does not exist, //给定一个flavoe，会返回DeciveMaster* 如果不存在会创建并且初始化
* it will be created and initialized.
* Note: the first call to this is not thread-safe. //第一次调用thread-safe不是这个？
* @return nullptr if initialization failed (and errno will be set) //初始化失败返回一个nullptr
*/
uORB::DeviceMaster *get_device_master(Flavor flavor);
// ==== uORB interface methods ====
/**
* Advertise as the publisher of a topic. //广告作为发布话题
*
* This performs the initial advertisement of a topic; it creates the topic //执行初始化的广告topic；它创造topic
* node in /obj if required and publishes the initial data.
*
* Any number of advertisers may publish to a topic; publications are atomic
* but co-ordination between publishers is not provided by the ORB.
*
* Internally this will call orb_advertise_multi with an instance of 0 and //函数内部调用了orb_advertis_multi
* default priority.
*
* @param meta The uORB metadata (usually from the ORB_ID() macro) //uORB metadata(通常来自ORB_ID()宏）作为topic
* for the topic.
* @param data A pointer to the initial data to be published. //数据指针
* For topics updated by interrupt handlers, the advertisement //中断处理函数
* must be performed from non-interrupt context. //必须执行无中断的内容
* @param queue_size Maximum number of buffered elements. If this is 1, no queuing is //最大的buffer元素个数，如果是1，没有队列被使用
* used.
* @return nullptr on error, otherwise returns an object pointer //返回空指针如果错误，否则返回一个类指针
* that can be used to publish to the topic. //那个可以用来公布topic
* If the topic in question is not known (due to an //如果topic在问题中不被知道（由于ORB_DEFINE不和ORB_DECLARE一致）
* ORB_DEFINE with no corresponding ORB_DECLARE)
* this function will return nullptr and set errno to ENOENT. //这个函数将会返回nullptr并且设置errno到ENOENT
*/
orb_advert_t orb_advertise(const struct orb_metadata *meta, const void *data, unsigned int queue_size = 1)
{
return orb_advertise_multi(meta, data, nullptr, ORB_PRIO_DEFAULT, queue_size);
}
/**
* Advertise as the publisher of a topic.
*
* This performs the initial advertisement of a topic; it creates the topic
* node in /obj if required and publishes the initial data.
*
* Any number of advertisers may publish to a topic; publications are atomic
* but co-ordination between publishers is not provided by the ORB.
*
* The multi can be used to create multiple independent instances of the same topic //用来创建多个独立接口用于相同的topic
* (each instance has its own buffer). //每个接口都有自己的buff
* This is useful for multiple publishers who publish the same topic. The subscriber
* then subscribes to all instances and chooses which source he wants to use.
*
* @param meta The uORB metadata (usually from the ORB_ID() macro) //meta通常来自于ORB_ID()宏，是uORB的metadata
* for the topic.
* @param data A pointer to the initial data to be published. //data是一个初始化要发布数据的指针
* For topics updated by interrupt handlers, the advertisement //通过中断处理函数更新，
* must be performed from non-interrupt context.
* @param instance Pointer to an integer which will yield the instance ID (0-based) //一个整形指针，用于接口ID（0-based)
* of the publication. This is an output parameter and will be set to the newly //创建接口等等，0是第一个广告，1是下一个，如此往下
* created instance, ie. 0 for the first advertiser, 1 for the next and so on.
* @param priority The priority of the instance. If a subscriber subscribes multiple //接口的优先级
* instances, the priority allows the subscriber to prioritize the best
* data source as long as its available. The subscriber is responsible to check
* and handle different priorities (@see orb_priority()).
* @param queue_size Maximum number of buffered elements. If this is 1, no queuing is //最大的buffer元素个数，如果是1，没有queuing被使用
* used.
* @return ERROR on error, otherwise returns a handle //返回ERROR在错误时，否则返回一个句柄。用于创建一个topic和publish
* that can be used to publish to the topic.
* If the topic in question is not known (due to an
* ORB_DEFINE with no corresponding ORB_DECLARE)
* this function will return -1 and set errno to ENOENT.
*/
orb_advert_t orb_advertise_multi(const struct orb_metadata *meta, const void *data, int *instance,
int priority, unsigned int queue_size = 1) ;
/**
* Unadvertise a topic.
*
* @param handle handle returned by orb_advertise or orb_advertise_multi. //用于取消一个topic， handle是orb_advertise_multi返回的handle
* @return 0 on success
*/
int orb_unadvertise(orb_advert_t handle);
/**
* Publish new data to a topic. //发布一个新的
*
* The data is atomically published to the topic and any waiting subscribers
* will be notified. Subscribers that are not waiting can check the topic
* for updates using orb_check and/or orb_stat.
*
* @param meta The uORB metadata (usually from the ORB_ID() macro) //从ORB_ID宏的metadata
* for the topic.
* @handle The handle returned from orb_advertise. //orb_advertise返回的handle
* @param data A pointer to the data to be published. //publish的数据的指针
* @return OK on success, ERROR otherwise with errno set accordingly. //返回OK如果成功
*/
int orb_publish(const struct orb_metadata *meta, orb_advert_t handle, const void *data) ;
/**
* Subscribe to a topic. //订阅一个topic
*
* The returned value is a file descriptor that can be passed to poll()
* in order to wait for updates to a topic, as well as topic_read,
* orb_check and orb_stat.
*
* Subscription will succeed even if the topic has not been advertised;
* in this case the topic will have a timestamp of zero, it will never
* signal a poll() event, checking will always return false and it cannot
* be copied. When the topic is subsequently advertised, poll, check,
* stat and copy calls will react to the initial publication that is
* performed as part of the advertisement.
*
* Subscription will fail if the topic is not known to the system, i.e.
* there is nothing in the system that has declared the topic and thus it
* can never be published.
*
* Internally this will call orb_subscribe_multi with instance 0.
*
* @param meta The uORB metadata (usually from the ORB_ID() macro) //订阅主题的metadata
* for the topic.
* @return ERROR on error, otherwise returns a handle
* that can be used to read and update the topic.
*/
int orb_subscribe(const struct orb_metadata *meta) ;
/**
* Subscribe to a multi-instance of a topic. //订阅多个主题
*
* The returned value is a file descriptor that can be passed to poll()
* in order to wait for updates to a topic, as well as topic_read,
* orb_check and orb_stat.
*
* Subscription will succeed even if the topic has not been advertised;
* in this case the topic will have a timestamp of zero, it will never
* signal a poll() event, checking will always return false and it cannot
* be copied. When the topic is subsequently advertised, poll, check,
* stat and copy calls will react to the initial publication that is
* performed as part of the advertisement.
*
* Subscription will fail if the topic is not known to the system, i.e.
* there is nothing in the system that has declared the topic and thus it
* can never be published.
*
* If a publisher publishes multiple instances the subscriber should
* subscribe to each instance with orb_subscribe_multi
* (@see orb_advertise_multi()).
*
* @param meta The uORB metadata (usually from the ORB_ID() macro)
* for the topic.
* @param instance The instance of the topic. Instance 0 matches the
* topic of the orb_subscribe() call, higher indices
* are for topics created with orb_advertise_multi().
* @return ERROR on error, otherwise returns a handle
* that can be used to read and update the topic.
* If the topic in question is not known (due to an
* ORB_DEFINE_OPTIONAL with no corresponding ORB_DECLARE)
* this function will return -1 and set errno to ENOENT.
*/
int orb_subscribe_multi(const struct orb_metadata *meta, unsigned instance) ;
/**
* Unsubscribe from a topic.
*
* @param handle A handle returned from orb_subscribe.
* @return OK on success, ERROR otherwise with errno set accordingly.
*/
int orb_unsubscribe(int handle) ; //取消订阅一个主题,handle是orb_subscribe返回的句柄
/**
* Fetch data from a topic.
*
* This is the only operation that will reset the internal marker that
* indicates that a topic has been updated for a subscriber. Once poll
* or check return indicating that an updaet is available, this call
* must be used to update the subscription.
*
* @param meta The uORB metadata (usually from the ORB_ID() macro)
* for the topic.
* @param handle A handle returned from orb_subscribe.
* @param buffer Pointer to the buffer receiving the data, or NULL
* if the caller wants to clear the updated flag without
* using the data.
* @return OK on success, ERROR otherwise with errno set accordingly.
*/
int orb_copy(const struct orb_metadata *meta, int handle, void *buffer) ; //从主题中获取数据，buffer就是接收数据存放的位置
/**
* Check whether a topic has been published to since the last orb_copy.
*
* This check can be used to determine whether to copy the topic when
* not using poll(), or to avoid the overhead of calling poll() when the
* topic is likely to have updated.
*
* Updates are tracked on a per-handle basis; this call will continue to
* return true until orb_copy is called using the same handle. This interface
* should be preferred over calling orb_stat due to the race window between
* stat and copy that can lead t
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