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

[Niklas Söderlund]

Hi Laurent,

On 2019-11-21 05:11:53 +0200, Laurent Pinchart wrote:
> 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.

You convinced me, I have restored the request reference in the next 
version.

> 
> > > > ---
> > > >  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

-- 
Regards,
Niklas Söderlund