[libcamera-devel] [PATCH v2 1/2] android: Post-pone fences reset in capture result

[Jacopo Mondi]

Hi Laurent,

On Tue, Sep 28, 2021 at 03:51:52AM +0300, Laurent Pinchart wrote:
> Hi Jacopo,
>
> Thank you for the patch.
>
> On Mon, Sep 27, 2021 at 11:36:59PM +0200, Jacopo Mondi wrote:
> > When a request has been completed and a new capture_result is created
> > we assumed all fences had been waited on, hence we set both
>
> Maybe "we assumed we have waited for all the fences to be signalled" ?
>
> > the release and acquisition fences to -1.
>
> s/acquisition/acquire/
>
> same below
>
> > As no buffer is queued to libcamera::Camera for streams of type Mapped,
> > their acquisition fences went ignored. Prepare to fix that by
> > by moving fences resetting after post-processing, that will be
> > instrumented to handle fences in the next patch.
> >
> > Also correct the release_fence handling for failed captures, as the
> > framework requires the release fences to be set to the acquire fence
> > value if the acquire fence has not been waited on.
> >
> > Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> > Reviewed-by: Hirokazu Honda <hiroh at chromium.org>
> > ---
> >  src/android/camera_device.cpp | 44 ++++++++++++++++++++++++-----------
> >  1 file changed, 31 insertions(+), 13 deletions(-)
> >
> > diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
> > index 21844e5114a9..3c9609d74402 100644
> > --- a/src/android/camera_device.cpp
> > +++ b/src/android/camera_device.cpp
> > @@ -1098,22 +1098,10 @@ void CameraDevice::requestComplete(Request *request)
> >  	}
> >  	Camera3RequestDescriptor &descriptor = node.mapped();
> >
> > -	/*
> > -	 * Prepare the capture result for the Android camera stack.
> > -	 *
> > -	 * The buffer status is set to OK and later changed to ERROR if
> > -	 * post-processing/compression fails.
> > -	 */
> >  	camera3_capture_result_t captureResult = {};
> >  	captureResult.frame_number = descriptor.frameNumber_;
> >  	captureResult.num_output_buffers = descriptor.buffers_.size();
> > -	for (camera3_stream_buffer_t &buffer : descriptor.buffers_) {
> > -		buffer.acquire_fence = -1;
> > -		buffer.release_fence = -1;
> > -		buffer.status = CAMERA3_BUFFER_STATUS_OK;
> > -	}
> >  	captureResult.output_buffers = descriptor.buffers_.data();
> > -	captureResult.partial_result = 1;
> >
> >  	/*
> >  	 * If the Request has failed, abort the request by notifying the error
> > @@ -1128,8 +1116,27 @@ void CameraDevice::requestComplete(Request *request)
> >  			    CAMERA3_MSG_ERROR_REQUEST);
> >
> >  		captureResult.partial_result = 0;
> > -		for (camera3_stream_buffer_t &buffer : descriptor.buffers_)
> > +		for (camera3_stream_buffer_t &buffer : descriptor.buffers_) {
> > +			CameraStream *cameraStream =
> > +				static_cast<CameraStream *>(buffer.stream->priv);
> > +
> > +			/*
> > +			 * Streams of type Direct have been queued to the
> > +			 * libcamera::Camera and their acquisition fences has
>
> s/has/have/
>
> > +			 * already been waited on by the CameraWorker.
> > +			 *
> > +			 * For other stream types signal to the framework the
> > +			 * acquisition fence has not been waited on, by setting
> > +			 * the release fence to its value.
> > +			 */
> > +			if (cameraStream->type() == CameraStream::Type::Direct)
> > +				buffer.release_fence = -1;
> > +			else
> > +				buffer.release_fence = buffer.acquire_fence;
> > +
> > +			buffer.acquire_fence = -1;
> >  			buffer.status = CAMERA3_BUFFER_STATUS_ERROR;
> > +		}
>
> Blank line here.
>
> >  		callbacks_->process_capture_result(callbacks_, &captureResult);
> >
> >  		return;
> > @@ -1196,6 +1203,17 @@ void CameraDevice::requestComplete(Request *request)
> >  		}
> >  	}
> >
> > +	/*
> > +	 * Finalize the capture result by setting fences and buffer status
> > +	 * before executing the callback.
> > +	 */
> > +	for (camera3_stream_buffer_t &buffer : descriptor.buffers_) {
> > +		buffer.acquire_fence = -1;
>
> Ideally, it would be nice to set the acquire_fence to -1 in
> CameraWorker::Worker::waitFence(), just after closing the fence fd.
> That's not possible yet, as the CameraWorker doesn't have access to the
> descriptor. This will be fixed by Umang's work, but I don't think we
> should wait until it gets merged. A \todo comment here would be good
> though.
>
> If we could set acquire_fence to -1 right after waiting, the above code
> would also be simplified, you could write
>
> 			buffer.release_fence = buffer.acquire_fence;
>
> regardless of the stream type.

I considered that too, but it required giving the full descriptor to
the camera worker, something that would conflict with what Umang is
doing.

>
> > +		buffer.release_fence = -1;
> > +		buffer.status = CAMERA3_BUFFER_STATUS_OK;
>
> This will override the buffer status set to CAMERA3_BUFFER_STATUS_ERROR
> in case post-processing fails. I think it would be easier to keep
> setting buffer.status to CAMERA3_BUFFER_STATUS_OK at the beginning of
> this function to avoid this problem. And if you keep the loop, you could
> as well set release_fence to -1 there too, but that's up to you.

Ah crabs, yes, we call the callback in the same path, sorry, I'll fix!

>
> > +	}
> > +	captureResult.partial_result = 1;
> > +
> >  	captureResult.result = resultMetadata->get();
> >  	callbacks_->process_capture_result(callbacks_, &captureResult);
> >  }
>
> --
> Regards,
>
> Laurent Pinchart