[libcamera-devel] [PATCH 1/5] libcamera: media_device: Provide the default entity

[Laurent Pinchart]

Hello,

On Thu, Feb 07, 2019 at 11:06:20PM +0100, Jacopo Mondi wrote:
> Hi Kieran,
>     ignorant question, is FL_DEFAULT an UVC specific thing?

It isn't, but it isn't widely used either. It would thus be fine using
the default entity in UVC-specific tests or in the UVC pipeline handler,
but not in the rest of the code, at least not without a fallback.

> A quick grep on kernel sources returns:
> 
> $ git grep FL_DEFAULT drivers/media/
> drivers/media/platform/omap3isp/ispresizer.c:   res->video_out.video.entity.flags |= MEDIA_ENT_FL_DEFAULT;
> drivers/media/usb/uvc/uvc_entity.c:             entity->vdev->entity.flags |= MEDIA_ENT_FL_DEFAULT;
> 
> So I guess not, as omap3 seems also omap3 uses that as well.
> 
> If that's not a UVC specificity, I welcome this change.
> 
> On Thu, Feb 07, 2019 at 09:21:15PM +0000, Kieran Bingham wrote:
> > Add a helper to identify the default entity from a media device.
> >
> > Utilise it in the two places which iterate the entities manually, to allocated
> > a V4L2Device from the default entity.
> >
> > Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> > ---
> >  src/libcamera/include/media_device.h  |  1 +
> >  src/libcamera/media_device.cpp        | 15 +++++++++++++++
> >  src/libcamera/pipeline/uvcvideo.cpp   | 10 ++++------
> >  test/v4l2_device/v4l2_device_test.cpp | 12 +++++-------
> >  4 files changed, 25 insertions(+), 13 deletions(-)
> >
> > diff --git a/src/libcamera/include/media_device.h b/src/libcamera/include/media_device.h
> > index 9f038093b2b2..361e8f4a4b86 100644
> > --- a/src/libcamera/include/media_device.h
> > +++ b/src/libcamera/include/media_device.h
> > @@ -42,6 +42,7 @@ public:
> >
> >  	const std::vector<MediaEntity *> &entities() const { return entities_; }
> >  	MediaEntity *getEntityByName(const std::string &name) const;
> > +	MediaEntity *defaultEntity() const;

This should take an entity type as a parameter as the default flag is
defined as "Default entity for its type". It could also be used, for
instance, to discover the default camera sensor.

> >
> >  	MediaLink *link(const std::string &sourceName, unsigned int sourceIdx,
> >  			const std::string &sinkName, unsigned int sinkIdx);
> > diff --git a/src/libcamera/media_device.cpp b/src/libcamera/media_device.cpp
> > index 800ed330fe6d..4af90e1590a1 100644
> > --- a/src/libcamera/media_device.cpp
> > +++ b/src/libcamera/media_device.cpp
> > @@ -319,6 +319,21 @@ MediaEntity *MediaDevice::getEntityByName(const std::string &name) const
> >  	return nullptr;
> >  }
> >
> > +/**
> > + * \brief Return the default MediaEntity within a MediaDevice
> > + * \return The default entity if specified, or a nullptr otherwise
> > + */
> > +MediaEntity *MediaDevice::defaultEntity() const
> > +{
> > +	for (MediaEntity *entity : entities_) {
> > +		if (entity->flags() & MEDIA_ENT_FL_DEFAULT) {
> > +			return entity;
> > +		}
> 
> You could drop the inner braces { } here
> > +	}
> > +
> > +	return nullptr;
> > +}
> > +
> >  /**
> >   * \brief Retrieve the MediaLink connecting two pads, identified by entity
> >   * names and pad indexes
> > diff --git a/src/libcamera/pipeline/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo.cpp
> > index fc31c52c0ecd..ed8228bb2fc6 100644
> > --- a/src/libcamera/pipeline/uvcvideo.cpp
> > +++ b/src/libcamera/pipeline/uvcvideo.cpp
> > @@ -146,13 +146,11 @@ bool PipelineHandlerUVC::match(DeviceEnumerator *enumerator)
> >
> >  	media_->acquire();
> >
> > -	for (MediaEntity *entity : media_->entities()) {
> > -		if (entity->flags() & MEDIA_ENT_FL_DEFAULT) {
> > -			video_ = new V4L2Device(entity);
> > -			break;
> > -		}
> > -	}
> > +	MediaEntity *entity = media_->defaultEntity();
> > +	if (!entity)
> 
> Looking at existing code if you don't find any DEFAULT entity, you
> return false as you do here, but also release the media device.
> 
> Should the same be done here?

I think it should, and a message should likely be logged too.

> > +		return false;
> >
> > +	video_ = new V4L2Device(entity);
> >  	if (!video_ || video_->open()) {
> >  		if (!video_)
> >  			LOG(UVC, Error) << "Could not find a default video device";
> > diff --git a/test/v4l2_device/v4l2_device_test.cpp b/test/v4l2_device/v4l2_device_test.cpp
> > index 18d014caf4c8..dd28cccada6b 100644
> > --- a/test/v4l2_device/v4l2_device_test.cpp
> > +++ b/test/v4l2_device/v4l2_device_test.cpp
> > @@ -46,15 +46,13 @@ int V4L2DeviceTest::init()
> >
> >  	media_->acquire();
> >
> > -	for (MediaEntity *entity : media_->entities()) {
> > -		if (entity->flags() & MEDIA_ENT_FL_DEFAULT) {
> > -			dev_ = new V4L2Device(entity);
> > -			break;
> > -		}
> > -	}
> > +	MediaEntity *entity = media_->defaultEntity();
> > +	if (!entity)
> > +		return TestFail;

Note that we're planning to use vivid instead of uvcvideo for V4L2Device
tests, so this may not be a good idea.

> > +	dev_ = new V4L2Device(entity);
> >  	if (!dev_)
> > -		return TestSkip;
> > +		return TestFail;
> >
> >  	return dev_->open();
> >  }

-- 
Regards,

Laurent Pinchart