[libcamera-devel] [RFC 03/12] libcamera: pipeline: Add helper to find request from buffer

[Laurent Pinchart]

Hi Niklas,

On Wed, Nov 20, 2019 at 05:33:56PM +0100, Niklas Söderlund wrote:
> On 2019-11-18 21:14:42 +0200, Laurent Pinchart wrote:
> > On Mon, Oct 28, 2019 at 03:25:16AM +0100, Niklas Söderlund wrote:
> > > The pipeline knows which buffer coming from the application belongs to
> > > which request. Add a helper to allow pipeline implementations to access
> > > this knowledge.
> > > 
> > > Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> > 
> > Why is this needed, given that Buffer stores a pointer to Request ? I
> > assume I'll find out later in the series, but it seems more efficient to
> > rely on the pointer.
> 
> This is needed as the Buffer will no longer keep a reference to a 
> Request.

But why can't it keep a reference to a request ? I understand the Buffer
object won't be transient anymore, but can't we still have a request
pointer, that will only be valid from the time the buffer is added to
the request to the time the request completes ? As long as we document
the lifetime of that pointer, I think it should be fine.

> > > ---
> > >  src/libcamera/include/pipeline_handler.h |  2 ++
> > >  src/libcamera/pipeline_handler.cpp       | 10 ++++++++++
> > >  2 files changed, 12 insertions(+)
> > > 
> > > diff --git a/src/libcamera/include/pipeline_handler.h b/src/libcamera/include/pipeline_handler.h
> > > index 320740746bc6e998..6024357e266c2e2b 100644
> > > --- a/src/libcamera/include/pipeline_handler.h
> > > +++ b/src/libcamera/include/pipeline_handler.h
> > > @@ -39,6 +39,8 @@ public:
> > >  	}
> > >  	virtual ~CameraData() {}
> > >  
> > > +	Request *requestFromBuffer(Buffer *buffer);
> > > +
> > >  	Camera *camera_;
> > >  	PipelineHandler *pipe_;
> > >  	std::list<Request *> queuedRequests_;
> > > diff --git a/src/libcamera/pipeline_handler.cpp b/src/libcamera/pipeline_handler.cpp
> > > index f9ae767d529d44d9..d70e286661aded8e 100644
> > > --- a/src/libcamera/pipeline_handler.cpp
> > > +++ b/src/libcamera/pipeline_handler.cpp
> > > @@ -58,6 +58,16 @@ LOG_DEFINE_CATEGORY(Pipeline)
> > >   * exists.
> > >   */
> > >  
> > > +Request *CameraData::requestFromBuffer(Buffer *buffer)
> > > +{
> > > +	for (Request *request : queuedRequests_)
> > > +		for (const auto &it : request->buffers())
> > > +			if (it.second == buffer)
> > > +				return request;
> > > +
> > > +	return nullptr;
> > > +}
> > > +
> > >  /**
> > >   * \var CameraData::camera_
> > >   * \brief The camera related to this CameraData instance

-- 
Regards,

Laurent Pinchart