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

[Jacopo Mondi]

Hi Laurent

On Mon, Nov 29, 2021 at 01:57:49AM +0200, Laurent Pinchart 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>

Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>

Thanks
  j

> ---
> Changes since v2:
>
> - Use FileDescriptor(UniqueFD &&) constructor
> - 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
>