[libcamera-devel] [PATCH v2 3/8] libcamera: pipeline_handler: Notify Request queueing failure

[Jacopo Mondi]

Hello,

On Mon, May 17, 2021 at 01:48:59PM +0900, Hirokazu Honda wrote:
> Hi Jacopo and Laurent,
>
> On Mon, May 17, 2021 at 11:45 AM Laurent Pinchart <
> laurent.pinchart at ideasonboard.com> wrote:
>
> > Hi Jacopo,
> >
> > Thank you for the patch.
> >
> > On Thu, May 13, 2021 at 11:22:41AM +0200, Jacopo Mondi wrote:
> > > Capture requests are queued by the PipelineHandler base class to each
> > > pipeline handler implementation using the virtual queueRequestDevice()
> > > function.
> > >
> > > However, if the pipeline handler fails to queue the request to the
> > > hardware, the request gets silently deleted from the list of queued
> > > ones, without notifying application of the error.
> > >
> > > Allowing applications to know if a Request has failed to queue
> > > by emitting the Camera::bufferCompleted and Camera::requestCompleted
> > > signals allows them to maintain a state consistent with the one
> > > internal to the library.
> > >
> > > To do so, if queuing a request to the device fails, cancel the request
> > > and emit the completion signal to report the failure to applications.
> > >
> > > Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> > > ---
> > >  src/libcamera/pipeline_handler.cpp | 15 ++++++++++++++-
> > >  1 file changed, 14 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/src/libcamera/pipeline_handler.cpp
> > b/src/libcamera/pipeline_handler.cpp
> > > index f41b7a7b3308..260a52018a4d 100644
> > > --- a/src/libcamera/pipeline_handler.cpp
> > > +++ b/src/libcamera/pipeline_handler.cpp
> > > @@ -391,6 +391,8 @@ bool PipelineHandler::hasPendingRequests(const
> > Camera *camera) const
> > >   * This method queues a capture request to the pipeline handler for
> > processing.
> > >   * The request is first added to the internal list of queued requests,
> > and
> > >   * then passed to the pipeline handler with a call to
> > queueRequestDevice().
> > > + * If the pipeline handler fails in queuing the request to the hardware
> > the
> > > + * request is immediately completed with error.
> > >   *
> > >   * Keeping track of queued requests ensures automatic completion of all
> > requests
> > >   * when the pipeline handler is stopped with stop(). Request completion
> > shall be
> > > @@ -409,8 +411,19 @@ void PipelineHandler::queueRequest(Request *request)
> > >       request->sequence_ = data->requestSequence_++;
> > >
> > >       int ret = queueRequestDevice(camera, request);
> > > -     if (ret)
> > > +     if (ret) {
> > > +             /*
> > > +              * Cancel the request and notify completion of its buffers
> > in
> > > +              * error state. Then complete the cancelled request and
> > remove
> > > +              * it from the queued requests list.
> > > +              */
> > > +             request->cancel();
> > > +             for (auto bufferMap : request->buffers())
> > > +                     camera->bufferCompleted.emit(request,
> > bufferMap.second);
> > > +
> > > +             camera->requestComplete(request);
> >
> > This breaks the request completion ordering. I think you could just call
> > PipelineHandler::completeRequest() instead.
> >
>
> I had the same comment in the previous version.
> https://patchwork.libcamera.org/patch/12243/
> We were waiting for your reply. Alright we got the reply now.
>

Yes, I've cc-ed Laurent in that patch to know his opinion.

Laurent, could you please read my reply and let me know if it add
anything to the discussion ?

Thanks
   j
>
>
> > >               data->queuedRequests_.remove(request);
> > > +     }
> > >  }
> > >
> > >  /**
> >
> > --
> > Regards,
> >
> > Laurent Pinchart
> >