[libcamera-devel] [PATCH] libcamera: pipeline: Fail match() when no camera is registered

[Laurent Pinchart]

Hi Jacopo,

On Wed, Oct 21, 2020 at 12:29:25PM +0200, Jacopo Mondi wrote:
> On Wed, Oct 21, 2020 at 03:24:16AM +0300, Laurent Pinchart wrote:
> > The rkisp1 and simple pipeline handlers can fail to register any camera,
> > if initialization of all the detected cameras fail. In that case, they
> > still return success from their match function. As no camera gets
> > registered, the pipeline handler is immediately destroyed, releasing the
> > acquired media devices, and the camera manager immediately tries to
> > match the same pipeline handler with the same media device, causing an
> > endless loop.
> >
> > Fix it by returning false from the match function if no camera gets
> > registered.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > ---
> >  src/libcamera/pipeline/rkisp1/rkisp1.cpp | 9 ++++++---
> >  src/libcamera/pipeline/simple/simple.cpp | 5 ++++-
> >  2 files changed, 10 insertions(+), 4 deletions(-)
> >
> > diff --git a/src/libcamera/pipeline/rkisp1/rkisp1.cpp b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> > index 2352ab3b234a..c74a2e9bd548 100644
> > --- a/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> > +++ b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> > @@ -1107,10 +1107,13 @@ bool PipelineHandlerRkISP1::match(DeviceEnumerator *enumerator)
> >  	if (!pad)
> >  		return false;
> >
> > -	for (MediaLink *link : pad->links())
> > -		createCamera(link->source()->entity());
> > +	bool registered = false;
> > +	for (MediaLink *link : pad->links()) {
> > +		if (!createCamera(link->source()->entity()))
> > +			registered = true;
> > +	}
> >
> > -	return true;
> > +	return registered;
> >  }
> >
> >  /* -----------------------------------------------------------------------------
> > diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> > index 8c00c0ffc121..8868a43beeb4 100644
> > --- a/src/libcamera/pipeline/simple/simple.cpp
> > +++ b/src/libcamera/pipeline/simple/simple.cpp
> > @@ -821,6 +821,8 @@ bool SimplePipelineHandler::match(DeviceEnumerator *enumerator)
> >  	}
> >
> >  	/* Initialize each pipeline and register a corresponding camera. */
> > +	bool registered = false;
> > +
> 
> Intentional empty line ?

Yes, I like a bit of space sometimes :-) I think I tend to not add a
blank line when the for statement itself operates on the variable that
was just declared.

> >  	for (std::unique_ptr<SimpleCameraData> &data : pipelines) {
> >  		int ret = data->init();
> >  		if (ret < 0)
> > @@ -830,9 +832,10 @@ bool SimplePipelineHandler::match(DeviceEnumerator *enumerator)
> >  			Camera::create(this, data->sensor_->id(),
> >  				       data->streams());
> >  		registerCamera(std::move(camera), std::move(data));
> > +		registered = true;
> 
> So the actual camera matching happens in data->init() here ?

Not so much the matching, but init() indeed analyzes the pipeline in
details to make sure everything is right, so it can fail. It shouldn't,
as we have an explicit match with the driver name table, but if
something wrong happens, it's best to avoid infinite loops.

> Anyway, looks good
> Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
> 
> >  	}
> >
> > -	return true;
> > +	return registered;
> >  }
> >
> >  V4L2VideoDevice *SimplePipelineHandler::video(const MediaEntity *entity)

-- 
Regards,

Laurent Pinchart