[libcamera-devel] [PATCH 2/2] libcamera: ipu3: Create CIO2 V4L2 devices

[Jacopo Mondi]

Hi Laurent,

On Fri, Jan 25, 2019 at 05:36:12PM +0200, Laurent Pinchart wrote:
> Hi Jacopo,
>
> On Thu, Jan 24, 2019 at 08:33:00PM +0100, Jacopo Mondi wrote:
> > On Thu, Jan 24, 2019 at 08:06:30PM +0100, Niklas Söderlund wrote:
> > > On 2019-01-24 12:30:20 +0100, Jacopo Mondi wrote:
> > >> Create V4L2 devices for the CIO2 capture video nodes and associate them
> > >> with the camera they are part of.
> > >>
> > >> Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> > >> ---
> > >>  src/libcamera/pipeline/ipu3/ipu3.cpp | 50 ++++++++++++++++++++++++++++
> > >>  1 file changed, 50 insertions(+)
> > >>
> > >> diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > >> index 8cbc10a..9f5a40f 100644
> > >> --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> > >> +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > >> @@ -15,6 +15,8 @@
> > >>  #include "log.h"
> > >>  #include "media_device.h"
> > >>  #include "pipeline_handler.h"
> > >> +#include "utils.h"
> > >> +#include "v4l2_device.h"
> > >>
> > >>  namespace libcamera {
> > >>
> > >> @@ -29,9 +31,19 @@ public:
> > >>  	bool match(CameraManager *manager, DeviceEnumerator *enumerator);
> > >>
> > >>  private:
> > >> +	class IPU3CameraData : public CameraData
> > >> +	{
> > >> +	public:
> > >> +		IPU3CameraData()
> > >> +			: dev_(nullptr) { }
> > >> +		~IPU3CameraData() { delete dev_; }
> > >> +		V4L2Device *dev_;
> > >> +	};
> > >> +
> > >>  	MediaDevice *cio2_;
> > >>  	MediaDevice *imgu_;
> > >>
> > >> +	V4L2Device *createVideoDevice(unsigned int id);
> > >>  	void registerCameras(CameraManager *manager);
> > >>  };
> > >>
> > >> @@ -122,6 +134,24 @@ error_release_mdev:
> > >>  	return false;
> > >>  }
> > >>
> > >> +/* Create video devices for the CIO2 unit associated with a camera. */
> > >> +V4L2Device *PipelineHandlerIPU3::createVideoDevice(unsigned int id)
> > >> +{
> > >> +	std::string cio2Name = "ipu3-cio2 " + std::to_string(id);
> > >> +	MediaEntity *cio2 = cio2_->getEntityByName(cio2Name);
> > >> +	if (!cio2)
> > >> +		return nullptr;
> > >> +
> > >> +	V4L2Device *dev = new V4L2Device(*cio2);
> > >> +	if (dev->open()) {
> > >> +		delete dev;
> > >> +		return nullptr;
> > >> +	}
> > >> +	dev->close();
> > >> +
> > >> +	return dev;
> > >> +}
> > >> +
> > >>  /*
> > >>   * Cameras are created associating an image sensor (represented by a
> > >>   * media entity with function MEDIA_ENT_F_CAM_SENSOR) to one of the four
> > >> @@ -172,6 +202,26 @@ void PipelineHandlerIPU3::registerCameras(CameraManager *manager)
> > >>
> > >>  		std::string cameraName = sensor->name() + " " + std::to_string(id);
> > >>  		std::shared_ptr<Camera> camera = Camera::create(cameraName);
> > >> +
> > >> +		setCameraData(camera.get(),
> > >> +			      std::move(utils::make_unique<IPU3CameraData>()));
> > >> +		IPU3CameraData *data =
> > >> +			reinterpret_cast<IPU3CameraData *>(cameraData(camera.get()));
> > >
> > > I'm not saying this is not needed, only that it looks a bit complex to
> > > my feeble mind. Could you educate me why the following would not work?
> > >
> > >     IPU3CameraData *data = new IPU3CameraData();
> > >     data->dev_ = videoDev;
> > >
> > >     setCameraData(camera.get(), data);
> >
> > setCameraData wants a unique_ptr. On the reason why we're passing it
> > by value (hence the std::move() ) instead than by reference and move()
> > inside the function see the discussion on v1. Basically, it makes
> > clear that after setCameraData() the local reference it's not
> > valid anymore.
> >
> > That said, I could indeed have created a unique_ptr<> from an already
> > existing reference, instead of using std::make_unique.
> >
> > What I have now looks like the following:
> >
> > 		V4L2Device *videoDev = createVideoDevice(id);
> > 		if (!videoDev) {
> > 			LOG(IPU3, Error)
> > 				<< "Failed to register camera["
> > 				<< numCameras << "] \"" << cameraName << "\"";
> > 			continue;
> > 		}
> >
> > 		IPU3CameraData *data = new IPU3CameraData(*videoDev);
> > 		setCameraData(camera.get(),
> > 			      std::move(std::unique_ptr<IPU3CameraData>(data)));
> > 		manager->addCamera(std::move(camera));
> >
> > Which is in my opinion nicer and equally safe. Thanks a lot for pointing
> > this out. Is it any better?
>
> How about
>
> 		std::unique_ptr<IPU3CameraData> data = utils::make_unique<IPU3CameraData>();
>  		data->dev_ = createVideoDevice(id);
>  		if (!data->dev_) {
>  			LOG(IPU3, Error)
>  				<< "Failed to register camera["
>  				<< numCameras << "] \"" << cameraName << "\"";
>  			continue;
>  		}
>
>  		setCameraData(camera.get(), std::move(data));
>  		manager->addCamera(std::move(camera));
>

Ok, but why is it better? I see an allocation which in case of failure
in creating the video device could be skipped.

Thanks
  j


> > > Apart from this I think this commit looks good.
> > >
> > >> +
> > >> +		/*
> > >> +		 * If V4L2 device creation fails, the Camera instance won't be
> > >> +		 * registered. The 'camera' shared pointer goes out of scope
> > >> +		 * and deletes the Camera it manages.
> > >> +		 */
> > >> +		V4L2Device *videoDev = createVideoDevice(id);
> > >> +		if (!videoDev) {
> > >> +			LOG(IPU3, Error)
> > >> +				<< "Failed to register camera["
> > >> +				<< numCameras << "] \"" << cameraName << "\"";
> > >> +			continue;
> > >> +		}
> > >> +
> > >> +		data->dev_ = videoDev;
> > >>  		manager->addCamera(std::move(camera));
> > >>
> > >>  		LOG(IPU3, Info)
>
> --
> Regards,
>
> Laurent Pinchart
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