PX4-Autopilot/src/modules/uORB/uORBMain.cpp

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 * modification, are permitted provided that the following conditions
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#include <string.h>

#include "uORBManager.hpp"
#include "uORB.h"
#include "uORBCommon.hpp"

#include <px4_platform_common/log.h>
#include <px4_platform_common/module.h>

extern "C" { __EXPORT int uorb_main(int argc, char *argv[]); }

static uORB::DeviceMaster *g_dev = nullptr;
static void usage()
{
	PRINT_MODULE_DESCRIPTION(
		R"DESCR_STR(
### Description
uORB is the internal pub-sub messaging system, used for communication between modules.

It is typically started as one of the very first modules and most other modules depend on it.

### Implementation
No thread or work queue is needed, the module start only makes sure to initialize the shared global state.
Communication is done via shared memory.
The implementation is asynchronous and lock-free, ie. a publisher does not wait for a subscriber and vice versa.
This is achieved by having a separate buffer between a publisher and a subscriber.

The code is optimized to minimize the memory footprint and the latency to exchange messages.

The interface is based on file descriptors: internally it uses `read`, `write` and `ioctl`. Except for the
publications, which use `orb_advert_t` handles, so that they can be used from interrupts as well (on NuttX).

Messages are defined in the `/msg` directory. They are converted into C/C++ code at build-time.

If compiled with ORB_USE_PUBLISHER_RULES, a file with uORB publication rules can be used to configure which
modules are allowed to publish which topics. This is used for system-wide replay.

### Examples
Monitor topic publication rates. Besides `top`, this is an important command for general system inspection:
$ uorb top
)DESCR_STR");

	PRINT_MODULE_USAGE_NAME("uorb", "communication");
	PRINT_MODULE_USAGE_COMMAND("start");
	PRINT_MODULE_USAGE_COMMAND_DESCR("status", "Print topic statistics");
	PRINT_MODULE_USAGE_COMMAND_DESCR("top", "Monitor topic publication rates");
	PRINT_MODULE_USAGE_PARAM_FLAG('a', "print all instead of only currently publishing topics with subscribers", true);
	PRINT_MODULE_USAGE_PARAM_FLAG('1', "run only once, then exit", true);
	PRINT_MODULE_USAGE_ARG("<filter1> [<filter2>]", "topic(s) to match (implies -a)", true);
}

int
uorb_main(int argc, char *argv[])
{
	if (argc < 2) {
		usage();
		return -EINVAL;
	}

	/*
	 * Start/load the driver.
	 */
	if (!strcmp(argv[1], "start")) {

		if (g_dev != nullptr) {
			PX4_WARN("already loaded");
			/* user wanted to start uorb, its already running, no error */
			return 0;
		}

		if (!uORB::Manager::initialize()) {
			PX4_ERR("uorb manager alloc failed");
			return -ENOMEM;
		}

		/* create the driver */
		g_dev = uORB::Manager::get_instance()->get_device_master();

		if (g_dev == nullptr) {
			return -errno;
		}

#if !defined(__PX4_QURT)
		/* 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.
	 */
	if (!strcmp(argv[1], "status")) {
		if (g_dev != nullptr) {
			g_dev->printStatistics();

		} else {
			PX4_INFO("uorb is not running");
		}

		return OK;
	}

	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;
}