libcamera: v4l2_videodevice: Add FrameBuffer interface

Add a new interface in parallel with the existing Buffer implementation
to also support FrameBuffer. The reason it's added in parallel is to aid
in the migration from Buffer to FrameBuffer throughout libcamera. With
this change discrete parts of libcamera can be migrated and tested
independently.

As the new interface is added in parallel there are some oddities in
this change which will be undone in a follow up patch once libcamera
have migrated away from the Buffer interface.

- There is a nasty hack in V4L2VideoDevice::bufferAvailable(). It is
  needed to allow both interfaces to exist and function at the same
  time. The idea is if buffers are allocated using the FrameBuffer
  interface V4L2VideoDevice::cache_ is set and we know to call the
  FrameBuffer 'buffer ready' signal, and likewise if it's not to call
  the Buffer variant.

- There is some code duplication between the two interfaces as they aim
  to solve the same thing in slightly different ways. As all Buffer
  related code is soon to be removed no effort to create code sharing
  between them have been made.

- Some function and variables which can't be distinguished by their
  argument types have been given a frameBuffer prefix instead of a
  buffer prefix. They are clearly documented in the code and will be
  renamed to the correct buffer prefix when the Buffer interface is
  removed.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 303 insertions, 10 deletions

diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index 84c45dbc..dd120129 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -410,7 +410,8 @@ const std::string V4L2DeviceFormat::toString() const
  * \param[in] deviceNode The file-system path to the video device node
  */
 V4L2VideoDevice::V4L2VideoDevice(const std::string &deviceNode)
-	: V4L2Device(deviceNode), bufferPool_(nullptr), fdEvent_(nullptr)
+	: V4L2Device(deviceNode), bufferPool_(nullptr), cache_(nullptr),
+	  fdEvent_(nullptr)
 {
 	/*
 	 * We default to an MMAP based CAPTURE video device, however this will
@@ -1075,6 +1076,94 @@ int V4L2VideoDevice::importBuffers(BufferPool *pool)
 	return 0;
 }
 
+/**
+ * \brief Allocate buffers from the video device
+ * \param[in] count Number of buffers to allocate
+ * \param[out] buffers Vector to store allocated buffers
+ * \return 0 on success or a negative error code otherwise
+ */
+int V4L2VideoDevice::exportBuffers(unsigned int count,
+				   std::vector<std::unique_ptr<FrameBuffer>> *buffers)
+{
+	if (cache_) {
+		LOG(V4L2, Error) << "Buffers already allocated";
+		return -EINVAL;
+	}
+
+	memoryType_ = V4L2_MEMORY_MMAP;
+
+	int ret = requestBuffers(count);
+	if (ret < 0)
+		return ret;
+
+	for (unsigned i = 0; i < count; ++i) {
+		struct v4l2_buffer buf = {};
+		struct v4l2_plane planes[VIDEO_MAX_PLANES] = {};
+
+		buf.index = i;
+		buf.type = bufferType_;
+		buf.memory = memoryType_;
+		buf.length = ARRAY_SIZE(planes);
+		buf.m.planes = planes;
+
+		ret = ioctl(VIDIOC_QUERYBUF, &buf);
+		if (ret < 0) {
+			LOG(V4L2, Error)
+				<< "Unable to query buffer " << i << ": "
+				<< strerror(-ret);
+			goto err_buf;
+		}
+
+		std::unique_ptr<FrameBuffer> buffer = createFrameBuffer(buf);
+		if (!buffer) {
+			LOG(V4L2, Error) << "Unable to create buffer";
+			ret = -EINVAL;
+			goto err_buf;
+		}
+
+		buffers->push_back(std::move(buffer));
+	}
+
+	cache_ = new V4L2BufferCache(*buffers);
+
+	return count;
+
+err_buf:
+	requestBuffers(0);
+
+	buffers->clear();
+
+	return ret;
+}
+
+std::unique_ptr<FrameBuffer>
+V4L2VideoDevice::createFrameBuffer(const struct v4l2_buffer &buf)
+{
+	const bool multiPlanar = V4L2_TYPE_IS_MULTIPLANAR(buf.type);
+	const unsigned int numPlanes = multiPlanar ? buf.length : 1;
+
+	if (numPlanes == 0 || numPlanes > VIDEO_MAX_PLANES) {
+		LOG(V4L2, Error) << "Invalid number of planes";
+		return nullptr;
+	}
+
+	std::vector<FrameBuffer::Plane> planes;
+	for (unsigned int nplane = 0; nplane < numPlanes; nplane++) {
+		FileDescriptor fd = exportDmabufFd(buf.index, nplane);
+		if (!fd.isValid())
+			return nullptr;
+
+		FrameBuffer::Plane plane;
+		plane.fd = std::move(fd);
+		plane.length = multiPlanar ?
+			buf.m.planes[nplane].length : buf.length;
+
+		planes.push_back(std::move(plane));
+	}
+
+	return utils::make_unique<FrameBuffer>(std::move(planes));
+}
+
 FileDescriptor V4L2VideoDevice::exportDmabufFd(unsigned int index,
 					       unsigned int plane)
 {
@@ -1097,13 +1186,40 @@ FileDescriptor V4L2VideoDevice::exportDmabufFd(unsigned int index,
 }
 
 /**
+ * \brief Prepare the device to import \a count buffers
+ * \param[in] count Number of buffers to prepare to import
+ * \return 0 on success or a negative error code otherwise
+ */
+int V4L2VideoDevice::importBuffers(unsigned int count)
+{
+	if (cache_) {
+		LOG(V4L2, Error) << "Buffers already allocated";
+		return -EINVAL;
+	}
+
+	memoryType_ = V4L2_MEMORY_DMABUF;
+
+	int ret = requestBuffers(count);
+	if (ret)
+		return ret;
+
+	cache_ = new V4L2BufferCache(count);
+
+	LOG(V4L2, Debug) << "Prepared to import " << count << " buffers";
+
+	return 0;
+}
+
+/**
  * \brief Release all internally allocated buffers
  */
 int V4L2VideoDevice::releaseBuffers()
 {
-	LOG(V4L2, Debug) << "Releasing bufferPool";
+	LOG(V4L2, Debug) << "Releasing buffers";
 
 	bufferPool_ = nullptr;
+	delete cache_;
+	cache_ = nullptr;
 
 	return requestBuffers(0);
 }
@@ -1223,6 +1339,90 @@ std::vector<std::unique_ptr<Buffer>> V4L2VideoDevice::queueAllBuffers()
 }
 
 /**
+ * \brief Queue a buffer to the video device
+ * \param[in] buffer The buffer to be queued
+ *
+ * For capture video devices the \a buffer will be filled with data by the
+ * device. For output video devices the \a buffer shall contain valid data and
+ * will be processed by the device. Once the device has finished processing the
+ * buffer, it will be available for dequeue.
+ *
+ * The best available V4L2 buffer is picked for \a buffer using the V4L2 buffer
+ * cache.
+ *
+ * \return 0 on success or a negative error code otherwise
+ */
+int V4L2VideoDevice::queueBuffer(FrameBuffer *buffer)
+{
+	struct v4l2_plane v4l2Planes[VIDEO_MAX_PLANES] = {};
+	struct v4l2_buffer buf = {};
+	int ret;
+
+	ret = cache_->get(*buffer);
+	if (ret < 0)
+		return ret;
+
+	buf.index = ret;
+	buf.type = bufferType_;
+	buf.memory = memoryType_;
+	buf.field = V4L2_FIELD_NONE;
+
+	bool multiPlanar = V4L2_TYPE_IS_MULTIPLANAR(buf.type);
+	const std::vector<FrameBuffer::Plane> &planes = buffer->planes();
+
+	if (buf.memory == V4L2_MEMORY_DMABUF) {
+		if (multiPlanar) {
+			for (unsigned int p = 0; p < planes.size(); ++p)
+				v4l2Planes[p].m.fd = planes[p].fd.fd();
+		} else {
+			buf.m.fd = planes[0].fd.fd();
+		}
+	}
+
+	if (multiPlanar) {
+		buf.length = planes.size();
+		buf.m.planes = v4l2Planes;
+	}
+
+	if (V4L2_TYPE_IS_OUTPUT(buf.type)) {
+		const FrameMetadata &metadata = buffer->metadata();
+
+		if (multiPlanar) {
+			unsigned int nplane = 0;
+			for (const FrameMetadata::Plane &plane : metadata.planes) {
+				v4l2Planes[nplane].bytesused = plane.bytesused;
+				v4l2Planes[nplane].length = buffer->planes()[nplane].length;
+				nplane++;
+			}
+		} else {
+			if (metadata.planes.size())
+				buf.bytesused = metadata.planes[0].bytesused;
+		}
+
+		buf.sequence = metadata.sequence;
+		buf.timestamp.tv_sec = metadata.timestamp / 1000000000;
+		buf.timestamp.tv_usec = (metadata.timestamp / 1000) % 1000000;
+	}
+
+	LOG(V4L2, Debug) << "Queueing buffer " << buf.index;
+
+	ret = ioctl(VIDIOC_QBUF, &buf);
+	if (ret < 0) {
+		LOG(V4L2, Error)
+			<< "Failed to queue buffer " << buf.index << ": "
+			<< strerror(-ret);
+		return ret;
+	}
+
+	if (queuedFrameBuffers_.empty())
+		fdEvent_->setEnabled(true);
+
+	queuedFrameBuffers_[buf.index] = buffer;
+
+	return 0;
+}
+
+/**
  * \brief Dequeue the next available buffer from the video device
  *
  * This method dequeues the next available buffer from the device. If no buffer
@@ -1281,17 +1481,97 @@ Buffer *V4L2VideoDevice::dequeueBuffer()
  * When this slot is called, a Buffer has become available from the device, and
  * will be emitted through the bufferReady Signal.
  *
- * For Capture video devices the Buffer will contain valid data.
- * For Output video devices the Buffer can be considered empty.
+ * For Capture video devices the FrameBuffer will contain valid data.
+ * For Output video devices the FrameBuffer can be considered empty.
  */
 void V4L2VideoDevice::bufferAvailable(EventNotifier *notifier)
 {
-	Buffer *buffer = dequeueBuffer();
-	if (!buffer)
-		return;
+	/*
+	 * This is a hack which allows both Buffer and FrameBuffer interfaces
+	 * to work with the same code base. This allows different parts of
+	 * libcamera to migrate to FrameBuffer in different patches.
+	 *
+	 * If we have a cache_ we know FrameBuffer is in use.
+	 *
+	 * \todo Remove this hack when the Buffer interface is removed.
+	 */
+	if (cache_) {
+		FrameBuffer *buffer = dequeueFrameBuffer();
+		if (!buffer)
+			return;
 
-	/* Notify anyone listening to the device. */
-	bufferReady.emit(buffer);
+		/* Notify anyone listening to the device. */
+		frameBufferReady.emit(buffer);
+	} else {
+		Buffer *buffer = dequeueBuffer();
+		if (!buffer)
+			return;
+
+		/* Notify anyone listening to the device. */
+		bufferReady.emit(buffer);
+	}
+}
+
+/**
+ * \brief Dequeue the next available buffer from the video device
+ *
+ * This method dequeues the next available buffer from the device. If no buffer
+ * is available to be dequeued it will return nullptr immediately.
+ *
+ * \todo Rename to dequeueBuffer() once the FrameBuffer transition is complete
+ *
+ * \return A pointer to the dequeued buffer on success, or nullptr otherwise
+ */
+FrameBuffer *V4L2VideoDevice::dequeueFrameBuffer()
+{
+	struct v4l2_buffer buf = {};
+	struct v4l2_plane planes[VIDEO_MAX_PLANES] = {};
+	int ret;
+
+	buf.type = bufferType_;
+	buf.memory = memoryType_;
+
+	bool multiPlanar = V4L2_TYPE_IS_MULTIPLANAR(buf.type);
+
+	if (multiPlanar) {
+		buf.length = VIDEO_MAX_PLANES;
+		buf.m.planes = planes;
+	}
+
+	ret = ioctl(VIDIOC_DQBUF, &buf);
+	if (ret < 0) {
+		LOG(V4L2, Error)
+			<< "Failed to dequeue buffer: " << strerror(-ret);
+		return nullptr;
+	}
+
+	LOG(V4L2, Debug) << "Dequeuing buffer " << buf.index;
+
+	cache_->put(buf.index);
+
+	auto it = queuedFrameBuffers_.find(buf.index);
+	FrameBuffer *buffer = it->second;
+	queuedFrameBuffers_.erase(it);
+
+	if (queuedFrameBuffers_.empty())
+		fdEvent_->setEnabled(false);
+
+	buffer->metadata_.status = buf.flags & V4L2_BUF_FLAG_ERROR
+				 ? FrameMetadata::FrameError
+				 : FrameMetadata::FrameSuccess;
+	buffer->metadata_.sequence = buf.sequence;
+	buffer->metadata_.timestamp = buf.timestamp.tv_sec * 1000000000ULL
+				    + buf.timestamp.tv_usec * 1000ULL;
+
+	buffer->metadata_.planes.clear();
+	if (multiPlanar) {
+		for (unsigned int nplane = 0; nplane < buf.length; nplane++)
+			buffer->metadata_.planes.push_back({ planes[nplane].bytesused });
+	} else {
+		buffer->metadata_.planes.push_back({ buf.bytesused });
+	}
+
+	return buffer;
 }
 
 /**
@@ -1300,6 +1580,11 @@ void V4L2VideoDevice::bufferAvailable(EventNotifier *notifier)
  */
 
 /**
+ * \var V4L2VideoDevice::frameBufferReady
+ * \brief A Signal emitted when a framebuffer completes
+ */
+
+/**
  * \brief Start the video stream
  * \return 0 on success or a negative error code otherwise
  */
@@ -1321,7 +1606,7 @@ int V4L2VideoDevice::streamOn()
  * \brief Stop the video stream
  *
  * Buffers that are still queued when the video stream is stopped are
- * immediately dequeued with their status set to Buffer::BufferError,
+ * immediately dequeued with their status set to FrameMetadata::FrameCancelled,
  * and the bufferReady signal is emitted for them. The order in which those
  * buffers are dequeued is not specified.
  *
@@ -1348,7 +1633,15 @@ int V4L2VideoDevice::streamOff()
 		bufferReady.emit(buffer);
 	}
 
+	for (auto it : queuedFrameBuffers_) {
+		FrameBuffer *buffer = it.second;
+
+		buffer->metadata_.status = FrameMetadata::FrameCancelled;
+		frameBufferReady.emit(buffer);
+	}
+
 	queuedBuffers_.clear();
+	queuedFrameBuffers_.clear();
 	fdEvent_->setEnabled(false);
 
 	return 0;