[libcamera-devel] [PATCH v3 14/17] libcamera: v4l2_videodevice: Use fd for a file descriptor

[Hirokazu Honda]

Hi Laurent,

On Mon, Nov 29, 2021 at 8:58 AM Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
>
> From: Hirokazu Honda <hiroh at chromium.org>
>
> Manages file descriptors owned by V4L2VideoDevice by UniqueFD.
> This also changes the return type of exportDmabufFd to UniqueFD
> from FileDescriptor in order to represent a caller owns the
> returned file file descriptor.
>
> Signed-off-by: Hirokazu Honda <hiroh at chromium.org>
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
> Changes since v2:
>
> - Use FileDescriptor(UniqueFD &&) constructor
I think this should be Use FileDescriptor(UniqueFD) constructor, but
it doesn't matter absolutely.

Reviewed-by: Hirokazu Honda <hiroh at chromium.org> if applicable.

> - Fix errno handling
> - Return {}
> ---
>  include/libcamera/internal/v4l2_videodevice.h |  4 +--
>  src/libcamera/v4l2_videodevice.cpp            | 30 ++++++++-----------
>  2 files changed, 15 insertions(+), 19 deletions(-)
>
> diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h
> index 4a44b7fd53b1..80b665771782 100644
> --- a/include/libcamera/internal/v4l2_videodevice.h
> +++ b/include/libcamera/internal/v4l2_videodevice.h
> @@ -19,6 +19,7 @@
>  #include <libcamera/base/class.h>
>  #include <libcamera/base/log.h>
>  #include <libcamera/base/signal.h>
> +#include <libcamera/base/unique_fd.h>
>
>  #include <libcamera/framebuffer.h>
>  #include <libcamera/geometry.h>
> @@ -31,7 +32,6 @@
>  namespace libcamera {
>
>  class EventNotifier;
> -class FileDescriptor;
>  class MediaDevice;
>  class MediaEntity;
>
> @@ -238,7 +238,7 @@ private:
>         int createBuffers(unsigned int count,
>                           std::vector<std::unique_ptr<FrameBuffer>> *buffers);
>         std::unique_ptr<FrameBuffer> createBuffer(unsigned int index);
> -       FileDescriptor exportDmabufFd(unsigned int index, unsigned int plane);
> +       UniqueFD exportDmabufFd(unsigned int index, unsigned int plane);
>
>         void bufferAvailable();
>         FrameBuffer *dequeueBuffer();
> diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> index c95626d33cc3..3966483a365f 100644
> --- a/src/libcamera/v4l2_videodevice.cpp
> +++ b/src/libcamera/v4l2_videodevice.cpp
> @@ -1320,12 +1320,12 @@ std::unique_ptr<FrameBuffer> V4L2VideoDevice::createBuffer(unsigned int index)
>
>         std::vector<FrameBuffer::Plane> planes;
>         for (unsigned int nplane = 0; nplane < numPlanes; nplane++) {
> -               FileDescriptor fd = exportDmabufFd(buf.index, nplane);
> +               UniqueFD fd = exportDmabufFd(buf.index, nplane);
>                 if (!fd.isValid())
>                         return nullptr;
>
>                 FrameBuffer::Plane plane;
> -               plane.fd = std::move(fd);
> +               plane.fd = FileDescriptor(std::move(fd));
>                 /*
>                  * V4L2 API doesn't provide dmabuf offset information of plane.
>                  * Set 0 as a placeholder offset.
> @@ -1380,8 +1380,8 @@ std::unique_ptr<FrameBuffer> V4L2VideoDevice::createBuffer(unsigned int index)
>         return std::make_unique<FrameBuffer>(planes);
>  }
>
> -FileDescriptor V4L2VideoDevice::exportDmabufFd(unsigned int index,
> -                                              unsigned int plane)
> +UniqueFD V4L2VideoDevice::exportDmabufFd(unsigned int index,
> +                                        unsigned int plane)
>  {
>         struct v4l2_exportbuffer expbuf = {};
>         int ret;
> @@ -1395,10 +1395,10 @@ FileDescriptor V4L2VideoDevice::exportDmabufFd(unsigned int index,
>         if (ret < 0) {
>                 LOG(V4L2, Error)
>                         << "Failed to export buffer: " << strerror(-ret);
> -               return FileDescriptor();
> +               return {};
>         }
>
> -       return FileDescriptor(std::move(expbuf.fd));
> +       return UniqueFD(expbuf.fd);
>  }
>
>  /**
> @@ -1896,7 +1896,6 @@ V4L2M2MDevice::~V4L2M2MDevice()
>   */
>  int V4L2M2MDevice::open()
>  {
> -       int fd;
>         int ret;
>
>         /*
> @@ -1905,30 +1904,27 @@ int V4L2M2MDevice::open()
>          * as the V4L2VideoDevice::open() retains a handle by duplicating the
>          * fd passed in.
>          */
> -       fd = syscall(SYS_openat, AT_FDCWD, deviceNode_.c_str(),
> -                    O_RDWR | O_NONBLOCK);
> -       if (fd < 0) {
> +       UniqueFD fd(syscall(SYS_openat, AT_FDCWD, deviceNode_.c_str(),
> +                           O_RDWR | O_NONBLOCK));
> +       if (!fd.isValid()) {
>                 ret = -errno;
> -               LOG(V4L2, Error)
> -                       << "Failed to open V4L2 M2M device: " << strerror(-ret);
> +               LOG(V4L2, Error) << "Failed to open V4L2 M2M device: "
> +                                << strerror(-ret);
>                 return ret;
>         }
>
> -       ret = output_->open(fd, V4L2_BUF_TYPE_VIDEO_OUTPUT);
> +       ret = output_->open(fd.get(), V4L2_BUF_TYPE_VIDEO_OUTPUT);
>         if (ret)
>                 goto err;
>
> -       ret = capture_->open(fd, V4L2_BUF_TYPE_VIDEO_CAPTURE);
> +       ret = capture_->open(fd.get(), V4L2_BUF_TYPE_VIDEO_CAPTURE);
>         if (ret)
>                 goto err;
>
> -       ::close(fd);
> -
>         return 0;
>
>  err:
>         close();
> -       ::close(fd);
>
>         return ret;
>  }
> --
> Regards,
>
> Laurent Pinchart
>