[libcamera-devel] [PATCH 15/30] cam: Move event loop execution from CameraSession to CamApp

[Laurent Pinchart]

Hi Kieran,

On Mon, Jul 12, 2021 at 04:25:07PM +0100, Kieran Bingham wrote:
> On 07/07/2021 03:19, Laurent Pinchart wrote:
> > To prepare for multiple concurrent camera sessions, move the event loop
> > exec() call from the CameraSession class to the CamApp class.
> 
> There we go - now that global loop access is becoming clearer.
> 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > ---
> >  src/cam/camera_session.cpp | 43 +++++++++++++++++---------------------
> >  src/cam/camera_session.h   |  6 ++++--
> >  src/cam/main.cpp           | 12 ++++++++++-
> >  3 files changed, 34 insertions(+), 27 deletions(-)
> > 
> > diff --git a/src/cam/camera_session.cpp b/src/cam/camera_session.cpp
> > index 16c1c66a285a..b1200e60329c 100644
> > --- a/src/cam/camera_session.cpp
> > +++ b/src/cam/camera_session.cpp
> > @@ -22,11 +22,11 @@ CameraSession::CameraSession(std::shared_ptr<Camera> camera,
> >  			     CameraConfiguration *config)
> >  	: camera_(camera), config_(config), writer_(nullptr), last_(0),
> >  	  queueCount_(0), captureCount_(0), captureLimit_(0),
> > -	  printMetadata_(false)
> > +	  printMetadata_(false), allocator_(nullptr)
> >  {
> >  }
> >  
> > -int CameraSession::run(const OptionsParser::Options &options)
> > +int CameraSession::start(const OptionsParser::Options &options)
> >  {
> >  	int ret;
> >  
> > @@ -61,36 +61,39 @@ int CameraSession::run(const OptionsParser::Options &options)
> >  			writer_ = new BufferWriter();
> >  	}
> >  
> > -	FrameBufferAllocator *allocator = new FrameBufferAllocator(camera_);
> > +	allocator_ = new FrameBufferAllocator(camera_);
> >  
> > -	ret = capture(allocator);
> > +	return startCapture();
> > +}
> >  
> > -	if (options.isSet(OptFile)) {
> > -		delete writer_;
> > -		writer_ = nullptr;
> > -	}
> > +void CameraSession::stop()
> > +{
> > +	int ret = camera_->stop();
> > +	if (ret)
> > +		std::cout << "Failed to stop capture" << std::endl;
> > +
> > +	delete writer_;
> > +	writer_ = nullptr;
> >  
> >  	requests_.clear();
> >  
> > -	delete allocator;
> > -
> > -	return ret;
> > +	delete allocator_;
> >  }
> >  
> > -int CameraSession::capture(FrameBufferAllocator *allocator)
> > +int CameraSession::startCapture()
> >  {
> >  	int ret;
> >  
> >  	/* Identify the stream with the least number of buffers. */
> >  	unsigned int nbuffers = UINT_MAX;
> >  	for (StreamConfiguration &cfg : *config_) {
> > -		ret = allocator->allocate(cfg.stream());
> > +		ret = allocator_->allocate(cfg.stream());
> >  		if (ret < 0) {
> >  			std::cerr << "Can't allocate buffers" << std::endl;
> >  			return -ENOMEM;
> >  		}
> >  
> > -		unsigned int allocated = allocator->buffers(cfg.stream()).size();
> > +		unsigned int allocated = allocator_->buffers(cfg.stream()).size();
> >  		nbuffers = std::min(nbuffers, allocated);
> >  	}
> >  
> > @@ -109,7 +112,7 @@ int CameraSession::capture(FrameBufferAllocator *allocator)
> >  		for (StreamConfiguration &cfg : *config_) {
> >  			Stream *stream = cfg.stream();
> >  			const std::vector<std::unique_ptr<FrameBuffer>> &buffers =
> > -				allocator->buffers(stream);
> > +				allocator_->buffers(stream);
> >  			const std::unique_ptr<FrameBuffer> &buffer = buffers[i];
> >  
> >  			ret = request->addBuffer(stream, buffer.get());
> > @@ -146,15 +149,7 @@ int CameraSession::capture(FrameBufferAllocator *allocator)
> >  	else
> >  		std::cout << "Capture until user interrupts by SIGINT" << std::endl;
> >  
> > -	ret = EventLoop::instance()->exec();
> 
> Without the context of the rest of the file at this point, is this the
> last EventLoop access?
> 
> I guess we're still waiting on the removal of
> 
> > +	EventLoop::instance()->callLater([=]() { processRequest(request); });
> 
> from 13/30 before we can remove event_loop.h from the headers.

This one stays, at least for now. We could probably change that, but
it's a common pattern to access the global event loop through a
singleton accessor. As this is specific to the cam application (qcam
probably has similar patterns, based on the Qt API that allows the same)
in any case, I think it's acceptable.

> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> > -	if (ret)
> > -		std::cout << "Failed to run capture loop" << std::endl;
> > -
> > -	ret = camera_->stop();
> > -	if (ret)
> > -		std::cout << "Failed to stop capture" << std::endl;
> > -
> > -	return ret;
> > +	return 0;
> >  }
> >  
> >  int CameraSession::queueRequest(Request *request)
> > diff --git a/src/cam/camera_session.h b/src/cam/camera_session.h
> > index 2728d7607db2..5131cfd48b4e 100644
> > --- a/src/cam/camera_session.h
> > +++ b/src/cam/camera_session.h
> > @@ -28,12 +28,13 @@ public:
> >  	CameraSession(std::shared_ptr<libcamera::Camera> camera,
> >  		      libcamera::CameraConfiguration *config);
> >  
> > -	int run(const OptionsParser::Options &options);
> > +	int start(const OptionsParser::Options &options);
> > +	void stop();
> >  
> >  	libcamera::Signal<> captureDone;
> >  
> >  private:
> > -	int capture(libcamera::FrameBufferAllocator *allocator);
> > +	int startCapture();
> >  
> >  	int queueRequest(libcamera::Request *request);
> >  	void requestComplete(libcamera::Request *request);
> > @@ -51,6 +52,7 @@ private:
> >  	unsigned int captureLimit_;
> >  	bool printMetadata_;
> >  
> > +	libcamera::FrameBufferAllocator *allocator_;
> >  	std::vector<std::unique_ptr<libcamera::Request>> requests_;
> >  };
> >  
> > diff --git a/src/cam/main.cpp b/src/cam/main.cpp
> > index a567a7cc7653..b13230c374ad 100644
> > --- a/src/cam/main.cpp
> > +++ b/src/cam/main.cpp
> > @@ -371,7 +371,17 @@ int CamApp::run()
> >  	if (options_.isSet(OptCapture)) {
> >  		CameraSession session(camera_, config_.get());
> >  		session.captureDone.connect(this, &CamApp::captureDone);
> > -		return session.run(options_);
> > +
> > +		ret = session.start(options_);
> > +		if (ret) {
> > +			std::cout << "Failed to start camera session" << std::endl;
> > +			return ret;
> > +		}
> > +
> > +		loop_.exec();
> > +
> > +		session.stop();
> > +		return 0;
> >  	}
> >  
> >  	if (options_.isSet(OptMonitor)) {

-- 
Regards,

Laurent Pinchart