[libcamera-devel] [PATCH 5/6] libcamera: ipu3: Create CIO2 V4L2 devices

[Laurent Pinchart]

Hi Jacopo,

On Tue, Jan 22, 2019 at 03:55:05PM +0100, Jacopo Mondi wrote:
> Hi Laurent,
>    this patch was sketeched out mainly to test creation of V4L2
> devices in the pipeline handler. When I wrote this I didn't think that
> each CIO2 device had to be associated with a Camera, but that's actually the
> case with the IPU3, so I welcome your suggestion to use this as an
> opportunity to start sketching out per camera specific data.
> 
> Remember though, that currently Cameras do not have a reference to
> their pipeline handlers, but that will be soon added I assume.

Yes, it is needed. Would you like to give it a try, solving all the
lifetime management issues it creates as you go ? :-)

> On Mon, Jan 21, 2019 at 10:53:52PM +0200, Laurent Pinchart wrote:
> > On Mon, Jan 21, 2019 at 06:27:04PM +0100, Jacopo Mondi wrote:
> >> Create V4L2 devices for the CIO2 capture video nodes.
> >>
> >> Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> >> ---
> >>  src/libcamera/pipeline/ipu3/ipu3.cpp | 36 +++++++++++++++++++++++++---
> >>  1 file changed, 33 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> >> index daf681c..0689ce8 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 {
> >>
> >> @@ -30,6 +32,9 @@ private:
> >>  	MediaDevice *cio2_;
> >>  	MediaDevice *imgu_;
> >>
> >> +	std::vector<std::unique_ptr<V4L2Device>> videoDevices_;
> >> +
> >
> > I think this is where you start needed per-camera data in the pipeline.
> > I would already model it as such.
> >
> >> +	void createVideoDevices();
> >>  	void registerCameras(CameraManager *manager);
> >>  };
> >>
> >> @@ -91,6 +96,12 @@ bool PipelineHandlerIPU3::match(CameraManager *manager, DeviceEnumerator *enumer
> >>  	cio2_->acquire();
> >>  	imgu_->acquire();
> >>
> >> +	/* Create video device nodes for CIO2 outputs */
> >> +	if (cio2_->open())
> >> +		goto error_release_mdev;
> >> +
> >
> > Do you need to open the cio2 media device to create the V4L2Device
> > instances ?
> 
> Possibly no, it has been enumerated already...
> 
> >> +	createVideoDevices();
> >> +
> >>  	/*
> >>  	 * Disable all links that are enabled by default on CIO2, as camera
> >>  	 * creation enables all valid links it finds.
> >> @@ -98,9 +109,6 @@ bool PipelineHandlerIPU3::match(CameraManager *manager, DeviceEnumerator *enumer
> >>  	 * Close the CIO2 media device after, as links are enabled and should
> >>  	 * not need to be changed after.
> >>  	 */
> >> -	if (cio2_->open())
> >> -		goto error_release_mdev;
> >> -
> >>  	if (cio2_->disableLinks())
> >>  		goto error_close_cio2;
> >>
> >> @@ -120,6 +128,28 @@ error_release_mdev:
> >>  	return false;
> >>  }
> >>
> >> +/*
> >> + * Create video devices for the CIO2 unit capture nodes and cache them
> >> + * for later reuse.
> >> + */
> >> +void PipelineHandlerIPU3::createVideoDevices()
> >> +{
> >> +	for (unsigned int id = 0; id < 3; ++id) {
> >
> > I assume you meant < 4 ?
> 
> Yes, I got confused by the 2 and the end of "cio2" :)
> 
> >> +		std::string cio2Name = "ipu3-cio2 " + std::to_string(id);
> >> +		MediaEntity *cio2 = cio2_->getEntityByName(cio2Name);
> >> +		if (!cio2)
> >> +			continue;
> >> +
> >> +		std::unique_ptr<V4L2Device> dev =
> >> +			utils::make_unique<V4L2Device>(*cio2);
> >
> > Do we really need to use std::unique_ptr<> for this ? Ownership of the
> > V4L2Device will never be transferred, so I assume ths reason is to get
> > the pointer deleted automatically. If you create a per-camera IPU3
> > pipeline object, you could embed V4L2Device in that object instead of
> > allocating it manually, which would achieve the same without using
> > std::unique_ptr<>.
> 
> Yes, automatic deletion was the reason.
> 
> I'll see how I should design this, but if I will need a sub-class of a
> generic base CameraData class, I should instantiate it with:
> 
>         camera.data = new IPU3CameraData()

Or possibly camera.setData(new IPU3CameraData()), with a camera.data()
accessor. This is especially important if you want to use
std::unique_ptr<> to store the camera data, as we'll need to borrow
references all the time, and having a data() accessor for that would be
simpler.

> and the problem of having to keep track of that instance (which might
> contain the V4L2 device) will represent itself, won't it?

You can either delete it in the destructor of the Camera class, or use a
std::unique_ptr<> to store it.

> >> +		if (dev->open())
> >> +			continue;
> >> +		dev->close();
> >> +
> >> +		videoDevices_.push_back(std::move(dev));
> >> +	}
> >
> > You should only create V4L2 devices for the CIO2 channels associated
> > with a camera, the other ones are not needed. I would advice splitting
> > the creation of cameras from registerCameras() to a registerCamera()
> > function, and moving creation of the V4L2 device there.
> 
> Agreed, let's use this to model Camera specific data.
> 
> >> +}
> >> +
> >>  /*
> >>   * Cameras are created associating an image sensor (represented by a
> >>   * media entity with function MEDIA_ENT_F_CAM_SENSOR) to one of the four

-- 
Regards,

Laurent Pinchart