[libcamera-devel] [PATCH v2 2/2] android: Wait on fences in CameraStream::process()

[Jacopo Mondi]

Hi Hiro,

On Tue, Sep 28, 2021 at 09:04:49AM +0900, Hirokazu Honda wrote:
> Hi Jacopo, thank you for the patch
>
> On Tue, Sep 28, 2021 at 6:36 AM Jacopo Mondi <jacopo at jmondi.org> wrote:
> >
> > Acquisition fences for streams of type Mapped generated by
> > post-processing, are not correctly handled and are currently
> > ignored by the camera HAL.
> >
> > Fix this by adding CameraStream::waitFence(), executed before
> > starting the post-processing in CameraStream::process().
> >
> > The change applies to all streams generated by post-processing (Mapped
> > and Internal) but currently acquire fences of Internal streams are
> > handled by the camera worker. Post-pone that to post-processing time by
> > passing -1 to the worker for Internal streams.
> >
> > The CameraStream::waitFence() implementation is copied from the
> > CameraWorker::Worker::waitFence() one, and both should be replaced by a
> > libcamera core mechanism.
> >
> > Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> > ---
> >  src/android/camera_device.cpp |  6 +++--
> >  src/android/camera_stream.cpp | 48 +++++++++++++++++++++++++++++++++--
> >  src/android/camera_stream.h   |  4 ++-
> >  3 files changed, 53 insertions(+), 5 deletions(-)
> >
> > diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
> > index 3c9609d74402..8b0caf2bda7d 100644
> > --- a/src/android/camera_device.cpp
> > +++ b/src/android/camera_device.cpp
> > @@ -973,6 +973,7 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
> >                 const camera3_stream_buffer_t &camera3Buffer = descriptor.buffers_[i];
> >                 camera3_stream *camera3Stream = camera3Buffer.stream;
> >                 CameraStream *cameraStream = static_cast<CameraStream *>(camera3Stream->priv);
> > +               int acquireFence = -1;
>
> I would like to have a comment that acquireFence -1 is passed in the
> case of Internal and reason.
> >
> >                 std::stringstream ss;
> >                 ss << i << " - (" << camera3Stream->width << "x"
> > @@ -1008,6 +1009,7 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
> >                                                   cameraStream->configuration().size));
> >
> >                         buffer = descriptor.frameBuffers_.back().get();
> > +                       acquireFence = camera3Buffer.acquire_fence;
> >                         LOG(HAL, Debug) << ss.str() << " (direct)";
> >                         break;
> >
> > @@ -1030,7 +1032,7 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
> >                 }
> >
> >                 descriptor.request_->addBuffer(cameraStream->stream(), buffer,
> > -                                               camera3Buffer.acquire_fence);
> > +                                              acquireFence);
> >         }
> >
> >         /*
> > @@ -1186,7 +1188,7 @@ void CameraDevice::requestComplete(Request *request)
> >                         continue;
> >                 }
> >
> > -               int ret = cameraStream->process(*src, *buffer.buffer,
> > +               int ret = cameraStream->process(*src, buffer,
> >                                                 descriptor.settings_,
> >                                                 resultMetadata.get());
> >                 /*
> > diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
> > index e30c7ee4fcb3..40dcb361749f 100644
> > --- a/src/android/camera_stream.cpp
> > +++ b/src/android/camera_stream.cpp
> > @@ -7,7 +7,10 @@
> >
> >  #include "camera_stream.h"
> >
> > +#include <errno.h>
> >  #include <sys/mman.h>
> > +#include <sys/poll.h>
> > +#include <unistd.h>
> >
> >  #include <libcamera/formats.h>
> >
> > @@ -109,11 +112,52 @@ int CameraStream::configure()
> >         return 0;
> >  }
> >
> > +int CameraStream::waitFence(int fence)
> > +{
> > +       /*
> > +        * \todo The implementation here is copied from camera_worker.cpp
> > +        * and both should be removed once libcamera is instrumented to handle
> > +        * fences waiting in the core.
> > +        *
> > +        * \todo Better characterize the timeout. Currently equal to the one
> > +        * used by the Rockchip Camera HAL on ChromeOS.
> > +        */
> > +       constexpr unsigned int timeoutMs = 300;
> > +       struct pollfd fds = { fence, POLLIN, 0 };
> > +
> > +       do {
> > +               int ret = poll(&fds, 1, timeoutMs);
> > +               if (ret == 0)
> > +                       return -ETIME;
> > +
> > +               if (ret > 0) {
> > +                       if (fds.revents & (POLLERR | POLLNVAL))
> > +                               return -EINVAL;
> > +
> > +                       return 0;
> > +               }
> > +       } while (errno == EINTR || errno == EAGAIN);
> > +
> > +       return -errno;
> > +}
> > +
> >  int CameraStream::process(const FrameBuffer &source,
> > -                         buffer_handle_t camera3Dest,
> > +                         camera3_stream_buffer_t &camera3Buffer,
> >                           const CameraMetadata &requestMetadata,
> >                           CameraMetadata *resultMetadata)
> >  {
> > +       /* Handle waiting on fences on the destination buffer. */
> > +       int fence = camera3Buffer.acquire_fence;
> > +       if (fence != -1) {
>
> Perhaps ASSERT(type_ == Internal || type_ == Mapped) is useful here?
>

I guess we can have fences set to -1 from the camera service, the
check for -1 here is for this reason, not to validate the stream type.

I can add the assertion, but it's an unrelated change.

> > +               int ret = waitFence(fence);
> > +               ::close(fence);
> > +               if (ret < 0) {
> > +                       LOG(HAL, Error) << "Failed waiting for fence: "
> > +                                       << fence << ": " << strerror(-ret);
> > +                       return ret;
> > +               }
> > +       }
> > +
> >         if (!postProcessor_)
> >                 return 0;
> >
> > @@ -122,7 +166,7 @@ int CameraStream::process(const FrameBuffer &source,
> >          * separate thread.
> >          */
> >         const StreamConfiguration &output = configuration();
> > -       CameraBuffer dest(camera3Dest, formats::MJPEG, output.size,
> > +       CameraBuffer dest(*camera3Buffer.buffer, formats::MJPEG, output.size,
> >                           PROT_READ | PROT_WRITE);
> >         if (!dest.isValid()) {
> >                 LOG(HAL, Error) << "Failed to map android blob buffer";
> > diff --git a/src/android/camera_stream.h b/src/android/camera_stream.h
> > index 2dab6c3a37d1..454a33dcdaaa 100644
> > --- a/src/android/camera_stream.h
> > +++ b/src/android/camera_stream.h
> > @@ -119,7 +119,7 @@ public:
> >
> >         int configure();
> >         int process(const libcamera::FrameBuffer &source,
> > -                   buffer_handle_t camera3Dest,
> > +                   camera3_stream_buffer_t &camera3Buffer,
> >                     const CameraMetadata &requestMetadata,
> >                     CameraMetadata *resultMetadata);
> >         libcamera::FrameBuffer *getBuffer();
> > @@ -140,6 +140,8 @@ private:
> >          */
> >         std::unique_ptr<std::mutex> mutex_;
> >         std::unique_ptr<PostProcessor> postProcessor_;
> > +
> > +       int waitFence(int fence);
>
> A function should be put before member variables.
>
> With these nits,
> Reviewed-by: Hirokazu Honda <hiroh at chromium.org>
>
> -Hiro
> >  };
> >
> >  #endif /* __ANDROID_CAMERA_STREAM__ */
> > --
> > 2.32.0
> >