[libcamera-devel] [PATCH v2 4/9] android: camera_device: Simplify FrameBuffer construction from a buffer_handle_t

[Laurent Pinchart]

Hi Kieran,

Thank you for the patch.

On Fri, Jul 03, 2020 at 01:25:59AM +0200, Niklas Söderlund wrote:
> On 2020-07-02 22:36:49 +0100, Kieran Bingham wrote:
> > Move the code which constructs a FrameBuffer from the Android buffer handle
> > to it's own function to simplify the code flow and readability.

s/it's/its/

> > 
> > Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> > ---
> >  src/android/camera_device.cpp | 35 +++++++++++++++++++----------------
> >  1 file changed, 19 insertions(+), 16 deletions(-)
> > 
> > diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
> > index 03dcdd520794..78ecfd7c2ee2 100644
> > --- a/src/android/camera_device.cpp
> > +++ b/src/android/camera_device.cpp
> > @@ -1011,6 +1011,24 @@ int CameraDevice::configureStreams(camera3_stream_configuration_t *stream_list)
> >  	return 0;
> >  }
> >  
> > +static FrameBuffer *newFrameBuffer(const buffer_handle_t camera3buffer)
> > +{
> > +	std::vector<FrameBuffer::Plane> planes;
> > +	for (unsigned int i = 0; i < 3; i++) {
> > +		FrameBuffer::Plane plane;
> > +		plane.fd = FileDescriptor(camera3buffer->data[i]);
> > +		/*
> > +		 * Setting length to zero here is OK as the length is only used
> > +		 * to map the memory of the plane. Libcamera do not need to poke
> > +		 * at the memory content queued by the HAL.
> > +		 */
> > +		plane.length = 0;
> > +		planes.push_back(std::move(plane));
> > +	}
> > +
> > +	return new FrameBuffer(std::move(planes));
> > +}
> > +
> >  int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Request)
> >  {
> >  	StreamConfiguration *streamConfiguration = &config_->at(0);
> > @@ -1064,22 +1082,7 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
> >  	 * Create a libcamera buffer using the dmabuf descriptors of the first
> >  	 * and (currently) only supported request buffer.
> >  	 */
> > -	const buffer_handle_t camera3Handle = *camera3Buffers[0].buffer;
> > -
> > -	std::vector<FrameBuffer::Plane> planes;
> > -	for (int i = 0; i < 3; i++) {
> > -		FrameBuffer::Plane plane;
> > -		plane.fd = FileDescriptor(camera3Handle->data[i]);
> > -		/*
> > -		 * Setting length to zero here is OK as the length is only used
> > -		 * to map the memory of the plane. Libcamera do not need to poke
> > -		 * at the memory content queued by the HAL.
> > -		 */
> > -		plane.length = 0;
> > -		planes.push_back(std::move(plane));
> > -	}
> > -
> > -	FrameBuffer *buffer = new FrameBuffer(std::move(planes));
> > +	FrameBuffer *buffer = newFrameBuffer(*camera3Buffers[0].buffer);
> 
> Would it make sens to change the argument to a pointer instead of 
> dereferencing it here?

buffer_handle_t is already a pointer, the function would then need to do

	plane.fd = FileDescriptor((*camera3buffer)->data[i]);

which isn't nice. I think it's best to dereference it once only here, in
the case function needs to access more than one field.

> Also I think I would callt the function 
> constructFrameBuffer() or createFrameBuffer().

I like createFrameBuffer() better, and I would make it a private member
of CameraDevice. With these changes,

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> >  	if (!buffer) {
> >  		LOG(HAL, Error) << "Failed to create buffer";
> >  		delete descriptor;

-- 
Regards,

Laurent Pinchart