[libcamera-devel] [PATCH 1/6] qcam: Tie FrameBufferAllocator to stream life

[Nicolas Dufresne]

Le jeu. 6 févr. 2020 10 h 05, Kieran Bingham <
kieran.bingham at ideasonboard.com> a écrit :

> The FrameBufferAllocator must be deleted and reconstructed before
> performing
> any reconfiguration of the stream.
>
> Construct the allocator at startCapture, and destroy it during stopCapture
> so
> that we can successfully stop and restart the stream.
>

Can you explain why adding this limitation. We have fixed this issue in v4l
with buffer orphaning, so I don't understand why introducing it again in
software.

Not being able to orphan the buffer pool actually prevents zero-copy
renegotiation. Consider the case where the framebuffer is being used as
your display scan out. You need to reconfigure and produce a new buffer
before this framebuffer can be returned.



> Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> ---
>  src/qcam/main_window.cpp | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/src/qcam/main_window.cpp b/src/qcam/main_window.cpp
> index df51fa888342..38bc04a23b86 100644
> --- a/src/qcam/main_window.cpp
> +++ b/src/qcam/main_window.cpp
> @@ -37,7 +37,6 @@ MainWindow::MainWindow(CameraManager *cm, const
> OptionsParser::Options &options)
>
>         ret = openCamera(cm);
>         if (!ret) {
> -               allocator_ = FrameBufferAllocator::create(camera_);
>                 ret = startCapture();
>         }
>
> @@ -50,7 +49,6 @@ MainWindow::~MainWindow()
>  {
>         if (camera_) {
>                 stopCapture();
> -               delete allocator_;
>                 camera_->release();
>                 camera_.reset();
>         }
> @@ -171,6 +169,7 @@ int MainWindow::startCapture()
>
>         adjustSize();
>
> +       allocator_ = FrameBufferAllocator::create(camera_);
>         ret = allocator_->allocate(stream);
>         if (ret < 0) {
>                 std::cerr << "Failed to allocate capture buffers" <<
> std::endl;
> @@ -255,6 +254,8 @@ void MainWindow::stopCapture()
>         }
>         mappedBuffers_.clear();
>
> +       delete allocator_;
> +
>         isCapturing_ = false;
>
>         config_.reset();
> --
> 2.20.1
>
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