[libcamera-devel] [RFC PATCH 07/10] libcamera: V4L2VideoDevice: Use fd for a file descriptor

[Hirokazu Honda]

V4L2VideoDevice deals with file descriptors. This uses ScopedFD
for them to avoid the leakage. This also changes the return type
of exportDmabufFd to ScopedFD from FileDescriptor in order to
represent a caller owns the returned file file descriptor.

Signed-off-by: Hirokazu Honda <hiroh at chromium.org>
---
 include/libcamera/internal/v4l2_videodevice.h |  4 ++--
 src/libcamera/v4l2_videodevice.cpp            | 21 ++++++++-----------
 2 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h
index 7938343b..925a8e82 100644
--- a/include/libcamera/internal/v4l2_videodevice.h
+++ b/include/libcamera/internal/v4l2_videodevice.h
@@ -30,9 +30,9 @@
 namespace libcamera {
 
 class EventNotifier;
-class FileDescriptor;
 class MediaDevice;
 class MediaEntity;
+class ScopedFD;
 
 struct V4L2Capability final : v4l2_capability {
 	const char *driver() const
@@ -235,7 +235,7 @@ 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);
+	ScopedFD exportDmabufFd(unsigned int index, unsigned int plane);
 
 	void bufferAvailable(EventNotifier *notifier);
 	FrameBuffer *dequeueBuffer();
diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index 0bf3b5f5..fe311ed9 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -1278,12 +1278,12 @@ 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);
+		ScopedFD fd = exportDmabufFd(buf.index, nplane);
 		if (!fd.isValid())
 			return nullptr;
 
 		FrameBuffer::Plane plane;
-		plane.fd = std::move(fd);
+		plane.fd = FileDescriptor(fd.release());
 		plane.length = multiPlanar ?
 			buf.m.planes[nplane].length : buf.length;
 
@@ -1293,7 +1293,7 @@ std::unique_ptr<FrameBuffer> V4L2VideoDevice::createBuffer(unsigned int index)
 	return std::make_unique<FrameBuffer>(std::move(planes));
 }
 
-FileDescriptor V4L2VideoDevice::exportDmabufFd(unsigned int index,
+ScopedFD V4L2VideoDevice::exportDmabufFd(unsigned int index,
 					       unsigned int plane)
 {
 	struct v4l2_exportbuffer expbuf = {};
@@ -1308,10 +1308,10 @@ FileDescriptor V4L2VideoDevice::exportDmabufFd(unsigned int index,
 	if (ret < 0) {
 		LOG(V4L2, Error)
 			<< "Failed to export buffer: " << strerror(-ret);
-		return FileDescriptor();
+		return ScopedFD();
 	}
 
-	return FileDescriptor(std::move(expbuf.fd));
+	return ScopedFD(expbuf.fd);
 }
 
 /**
@@ -1703,7 +1703,6 @@ V4L2M2MDevice::~V4L2M2MDevice()
  */
 int V4L2M2MDevice::open()
 {
-	int fd;
 	int ret;
 
 	/*
@@ -1712,7 +1711,7 @@ 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(),
+	int fd = syscall(SYS_openat, AT_FDCWD, deviceNode_.c_str(),
 		     O_RDWR | O_NONBLOCK);
 	if (fd < 0) {
 		ret = -errno;
@@ -1720,22 +1719,20 @@ int V4L2M2MDevice::open()
 			<< "Failed to open V4L2 M2M device: " << strerror(-ret);
 		return ret;
 	}
+	ScopedFD scopedFd(fd);
 
-	ret = output_->open(fd, V4L2_BUF_TYPE_VIDEO_OUTPUT);
+	ret = output_->open(scopedFd.get(), V4L2_BUF_TYPE_VIDEO_OUTPUT);
 	if (ret)
 		goto err;
 
-	ret = capture_->open(fd, V4L2_BUF_TYPE_VIDEO_CAPTURE);
+	ret = capture_->open(scopedFd.get(), V4L2_BUF_TYPE_VIDEO_CAPTURE);
 	if (ret)
 		goto err;
 
-	::close(fd);
-
 	return 0;
 
 err:
 	close();
-	::close(fd);
 
 	return ret;
 }
-- 
2.31.1.368.gbe11c130af-goog