[PATCH v7 2/7] libcamera: Remove PipelineHandler Fatal check of non-empty MediaDevices

[Jacopo Mondi]

Hi

On Sat, Aug 03, 2024 at 11:49:12PM GMT, Laurent Pinchart wrote:
> Hi Chenghao,
>
> Thank you for the patch.
>
> On Thu, Aug 01, 2024 at 07:30:58AM +0000, Harvey Yang wrote:
> > The Fatal check of having at least one MediaDevice was to prevent
> > pipeline handler implementations searching and owning media devices with
> > custom conventions, instead of using the base function
> > |acquireMediaDevice|. It also has the assumption that there's at least
> > one media device to make a camera work.
> >
> > Now that the assumption will be broken by the virtual pipeline handler
> > added in the following patches, and developers should be aware of the
> > available functions in the base class to handle media devices, the Fatal
> > check is no longer needed.
> >
> > Signed-off-by: Harvey Yang <chenghaoyang at chromium.org>
>
> That's a bit of a hack. It would be nicer to rework the device matching
> logic to support other types of devices than media devices. That would
> be quite a lot of yak shaving though, I suppose we can live with this
> patch for now.
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

More or less 1 year ago I worked on generalizing device matching
to support non-UVC compatible USB devices.

Is there anything that can be useful here ?
https://git.libcamera.org/libcamera/jmondi/libcamera.git/log/?h=jmondi/device-match-generalize

>
> > ---
> >  src/libcamera/pipeline_handler.cpp | 11 ++++++++---
> >  1 file changed, 8 insertions(+), 3 deletions(-)
> >
> > diff --git a/src/libcamera/pipeline_handler.cpp b/src/libcamera/pipeline_handler.cpp
> > index 5ea2ca78..125cf9d5 100644
> > --- a/src/libcamera/pipeline_handler.cpp
> > +++ b/src/libcamera/pipeline_handler.cpp
> > @@ -605,9 +605,14 @@ void PipelineHandler::registerCamera(std::shared_ptr<Camera> camera)
> >  {
> >  	cameras_.push_back(camera);
> >
> > -	if (mediaDevices_.empty())
> > -		LOG(Pipeline, Fatal)
> > -			<< "Registering camera with no media devices!";
> > +	if (mediaDevices_.empty()) {
> > +		/*
> > +		 * For virtual devices with no MediaDevice, there are no system
> > +		 * devices to register.
> > +		 */
> > +		manager_->_d()->addCamera(std::move(camera));
> > +		return;
> > +	}
> >
> >  	/*
> >  	 * Walk the entity list and map the devnums of all capture video nodes
>
> --
> Regards,
>
> Laurent Pinchart