libcamera: Rename V4L2Device to V4L2VideoDevice

In preparation of creating a new V4L2Device base class, rename
V4L2Device to V4L2VideoDevice.

This is a project wide rename without any intended functional change.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 1127 insertions, 0 deletions

diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
new file mode 100644
index 00000000..0e70498c
--- /dev/null
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -0,0 +1,1127 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * v4l2_videodevice.cpp - V4L2 Video Device
+ */
+
+#include "v4l2_videodevice.h"
+
+#include <fcntl.h>
+#include <iomanip>
+#include <sstream>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/time.h>
+#include <unistd.h>
+#include <vector>
+
+#include <libcamera/buffer.h>
+#include <libcamera/event_notifier.h>
+
+#include "log.h"
+#include "media_device.h"
+#include "media_object.h"
+
+/**
+ * \file v4l2_videodevice.h
+ * \brief V4L2 Video Device API
+ */
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(V4L2)
+
+/**
+ * \struct V4L2Capability
+ * \brief struct v4l2_capability object wrapper and helpers
+ *
+ * The V4L2Capability structure manages the information returned by the
+ * VIDIOC_QUERYCAP ioctl.
+ */
+
+/**
+ * \fn V4L2Capability::driver()
+ * \brief Retrieve the driver module name
+ * \return The string containing the name of the driver module
+ */
+
+/**
+ * \fn V4L2Capability::card()
+ * \brief Retrieve the device card name
+ * \return The string containing the device name
+ */
+
+/**
+ * \fn V4L2Capability::bus_info()
+ * \brief Retrieve the location of the device in the system
+ * \return The string containing the device location
+ */
+
+/**
+ * \fn V4L2Capability::device_caps()
+ * \brief Retrieve the capabilities of the device
+ * \return The device specific capabilities if V4L2_CAP_DEVICE_CAPS is set or
+ * 	   driver capabilities otherwise
+ */
+
+/**
+ * \fn V4L2Capability::isMultiplanar()
+ * \brief Identify if the device implements the V4L2 multiplanar APIs
+ * \return True if the device supports multiplanar APIs
+ */
+
+/**
+ * \fn V4L2Capability::isCapture()
+ * \brief Identify if the device captures data
+ * \return True if the device can capture data
+ */
+
+/**
+ * \fn V4L2Capability::isOutput()
+ * \brief Identify if the device outputs data
+ * \return True if the device can output data
+ */
+
+/**
+ * \fn V4L2Capability::isVideo()
+ * \brief Identify if the device captures or outputs images
+ * \return True if the device can capture or output images
+ */
+
+/**
+ * \fn V4L2Capability::isMeta()
+ * \brief Identify if the device captures or outputs image meta-data
+ *
+ * \todo Add support for META_CAPTURE introduced in Linux v5.0
+ *
+ * \return True if the device can capture or output image meta-data
+ */
+
+/**
+ * \fn V4L2Capability::isVideoCapture()
+ * \brief Identify if the device captures images
+ * \return True if the device can capture images
+ */
+
+/**
+ * \fn V4L2Capability::isVideoOutput()
+ * \brief Identify if the device outputs images
+ * \return True if the device can output images
+ */
+
+/**
+ * \fn V4L2Capability::isMetaCapture()
+ * \brief Identify if the device captures image meta-data
+ * \return True if the device can capture image meta-data
+ */
+
+/**
+ * \fn V4L2Capability::isMetaOutput()
+ * \brief Identify if the device outputs image meta-data
+ * \return True if the device can output image meta-data
+ */
+
+/**
+ * \fn V4L2Capability::hasStreaming()
+ * \brief Determine if the device can perform Streaming I/O
+ * \return True if the device provides Streaming I/O IOCTLs
+ */
+
+/**
+ * \class V4L2DeviceFormat
+ * \brief The V4L2 device image format and sizes
+ *
+ * This class describes the image format and resolution to be programmed on a
+ * V4L2 video device. The image format is defined by a fourcc code (as specified
+ * by the V4L2 API with the V4L2_PIX_FMT_* macros), a resolution (width and
+ * height) and one to three planes with configurable line stride and a total
+ * per-plane size in bytes.
+ *
+ * Image formats, as defined by the V4L2 APIs, are categorised as packed,
+ * semi-planar and planar, and describe the layout of the image pixel components
+ * stored in memory.
+ *
+ * Packed image formats store pixel components one after the other, in a
+ * contiguous memory area. Examples of packed image formats are YUYV
+ * permutations, RGB with different pixel sub-sampling ratios such as RGB565 or
+ * RGB666 or Raw-Bayer formats such as SRGGB8 or SGRBG12.
+ *
+ * Semi-planar and planar image formats store the pixel components in separate
+ * and possibly non-contiguous memory areas, named planes, whose sizes depend on
+ * the pixel components sub-sampling ratios, which are defined by the format.
+ * Semi-planar formats use two planes to store pixel components and notable
+ * examples of such formats are the NV12 and NV16 formats, while planar formats
+ * use three planes to store pixel components and notable examples are YUV422
+ * and YUV420.
+ *
+ * Image formats supported by the V4L2 API are defined and described in Section
+ * number 2 of the "Part I - Video for Linux API" chapter of the "Linux Media
+ * Infrastructure userspace API", part of the Linux kernel documentation.
+ *
+ * In the context of this document, packed image formats are referred to as
+ * "packed formats" and semi-planar and planar image formats are referred to as
+ * "planar formats".
+ *
+ * V4L2 also defines two different sets of APIs to work with devices that store
+ * planes in contiguous or separate memory areas. They are named "Single-plane
+ * APIs" and "Multi-plane APIs" respectively and are documented in Section 2.1
+ * and Section 2.2 of the above mentioned "Part I - Video for Linux API"
+ * documentation.
+ *
+ * The single-plane API allows, among other parameters, the configuration of the
+ * image resolution, the pixel format and the stride length. In that case the
+ * stride applies to all planes (possibly sub-sampled). The multi-plane API
+ * allows configuring the resolution, the pixel format and a per-plane stride
+ * length and total size.
+ *
+ * Packed image formats, which occupy a single memory area, are easily described
+ * through the single-plane API. When used on a device that implements the
+ * multi-plane API, only the size and stride information contained in the first
+ * plane are taken into account.
+ *
+ * Planar image formats, which occupy distinct memory areas, are easily
+ * described through the multi-plane APIs. When used on a device that implements
+ * the single-plane API, all planes are stored one after the other in a
+ * contiguous memory area, and it is not possible to configure per-plane stride
+ * length and size, but only a global stride length which is applied to all
+ * planes.
+ *
+ * The V4L2DeviceFormat class describes both packed and planar image formats,
+ * regardless of the API type (single or multi plane) implemented by the device
+ * the format has to be applied to. The total size and bytes per line of images
+ * represented with packed formats are configured using the first entry of the
+ * V4L2DeviceFormat::planes array, while the per-plane size and per-plane stride
+ * length of images represented with planar image formats are configured using
+ * the opportune number of entries of the V4L2DeviceFormat::planes array, as
+ * prescribed by the image format definition (semi-planar formats use 2 entries,
+ * while planar formats use the whole 3 entries). The number of valid entries of
+ * the V4L2DeviceFormat::planes array is defined by the
+ * V4L2DeviceFormat::planesCount value.
+ */
+
+/**
+ * \var V4L2DeviceFormat::size
+ * \brief The image size in pixels
+ */
+
+/**
+ * \var V4L2DeviceFormat::fourcc
+ * \brief The fourcc code describing the pixel encoding scheme
+ *
+ * The fourcc code, as defined by the V4L2 API with the V4L2_PIX_FMT_* macros,
+ * that identifies the image format pixel encoding scheme.
+ */
+
+/**
+ * \var V4L2DeviceFormat::planes
+ * \brief The per-plane memory size information
+ *
+ * Images are stored in memory in one or more data planes. Each data plane has a
+ * specific line stride and memory size, which could differ from the image
+ * visible sizes to accommodate padding at the end of lines and end of planes.
+ * Only the first \ref planesCount entries are considered valid.
+ */
+
+/**
+ * \var V4L2DeviceFormat::planesCount
+ * \brief The number of valid data planes
+ */
+
+/**
+ * \brief Assemble and return a string describing the format
+ * \return A string describing the V4L2DeviceFormat
+ */
+const std::string V4L2DeviceFormat::toString() const
+{
+	std::stringstream ss;
+
+	ss.fill(0);
+	ss << size.toString() << "-0x" << std::hex << std::setw(8) << fourcc;
+
+	return ss.str();
+}
+
+/**
+ * \class V4L2VideoDevice
+ * \brief V4L2VideoDevice object and API
+ *
+ * The V4L2 Device API class models an instance of a V4L2 device node.
+ * It is constructed with the path to a V4L2 video device node. The device node
+ * is only opened upon a call to open() which must be checked for success.
+ *
+ * The device capabilities are validated when the device is opened and the
+ * device is rejected if it is not a suitable V4L2 capture or output device, or
+ * if the device does not support streaming I/O.
+ *
+ * No API call other than open(), isOpen() and close() shall be called on an
+ * unopened device instance.
+ *
+ * The V4L2VideoDevice class tracks queued buffers and handles buffer events. It
+ * automatically dequeues completed buffers and emits the \ref bufferReady
+ * signal.
+ *
+ * Upon destruction any device left open will be closed, and any resources
+ * released.
+ */
+
+/**
+ * \brief Construct a V4L2VideoDevice
+ * \param[in] deviceNode The file-system path to the video device node
+ */
+V4L2VideoDevice::V4L2VideoDevice(const std::string &deviceNode)
+	: deviceNode_(deviceNode), fd_(-1), bufferPool_(nullptr),
+	  queuedBuffersCount_(0), fdEvent_(nullptr)
+{
+	/*
+	 * We default to an MMAP based CAPTURE device, however this will be
+	 * updated based upon the device capabilities.
+	 */
+	bufferType_ = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
+	memoryType_ = V4L2_MEMORY_MMAP;
+}
+
+/**
+ * \brief Construct a V4L2VideoDevice from a MediaEntity
+ * \param[in] entity The MediaEntity to build the device from
+ *
+ * Construct a V4L2VideoDevice from a MediaEntity's device node path.
+ */
+V4L2VideoDevice::V4L2VideoDevice(const MediaEntity *entity)
+	: V4L2VideoDevice(entity->deviceNode())
+{
+}
+
+V4L2VideoDevice::~V4L2VideoDevice()
+{
+	close();
+}
+
+/**
+ * \brief Open a V4L2 device and query its capabilities
+ * \return 0 on success or a negative error code otherwise
+ */
+int V4L2VideoDevice::open()
+{
+	int ret;
+
+	if (isOpen()) {
+		LOG(V4L2, Error) << "Device already open";
+		return -EBUSY;
+	}
+
+	ret = ::open(deviceNode_.c_str(), O_RDWR | O_NONBLOCK);
+	if (ret < 0) {
+		ret = -errno;
+		LOG(V4L2, Error)
+			<< "Failed to open V4L2 device: " << strerror(-ret);
+		return ret;
+	}
+	fd_ = ret;
+
+	ret = ioctl(fd_, VIDIOC_QUERYCAP, &caps_);
+	if (ret < 0) {
+		ret = -errno;
+		LOG(V4L2, Error)
+			<< "Failed to query device capabilities: "
+			<< strerror(-ret);
+		return ret;
+	}
+
+	LOG(V4L2, Debug)
+		<< "Opened device " << caps_.bus_info() << ": "
+		<< caps_.driver() << ": " << caps_.card();
+
+	if (!caps_.hasStreaming()) {
+		LOG(V4L2, Error) << "Device does not support streaming I/O";
+		return -EINVAL;
+	}
+
+	/*
+	 * Set buffer type and wait for read notifications on CAPTURE devices
+	 * (POLLIN), and write notifications for OUTPUT devices (POLLOUT).
+	 */
+	if (caps_.isVideoCapture()) {
+		fdEvent_ = new EventNotifier(fd_, EventNotifier::Read);
+		bufferType_ = caps_.isMultiplanar()
+			    ? V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
+			    : V4L2_BUF_TYPE_VIDEO_CAPTURE;
+	} else if (caps_.isVideoOutput()) {
+		fdEvent_ = new EventNotifier(fd_, EventNotifier::Write);
+		bufferType_ = caps_.isMultiplanar()
+			    ? V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE
+			    : V4L2_BUF_TYPE_VIDEO_OUTPUT;
+	} else if (caps_.isMetaCapture()) {
+		fdEvent_ = new EventNotifier(fd_, EventNotifier::Read);
+		bufferType_ = V4L2_BUF_TYPE_META_CAPTURE;
+	} else if (caps_.isMetaOutput()) {
+		fdEvent_ = new EventNotifier(fd_, EventNotifier::Write);
+		bufferType_ = V4L2_BUF_TYPE_META_OUTPUT;
+	} else {
+		LOG(V4L2, Error) << "Device is not a supported type";
+		return -EINVAL;
+	}
+
+	fdEvent_->activated.connect(this, &V4L2VideoDevice::bufferAvailable);
+	fdEvent_->setEnabled(false);
+
+	return 0;
+}
+
+/**
+ * \brief Check if device is successfully opened
+ * \return True if the device is open, false otherwise
+ */
+bool V4L2VideoDevice::isOpen() const
+{
+	return fd_ != -1;
+}
+
+/**
+ * \brief Close the device, releasing any resources acquired by open()
+ */
+void V4L2VideoDevice::close()
+{
+	if (fd_ < 0)
+		return;
+
+	releaseBuffers();
+	delete fdEvent_;
+
+	::close(fd_);
+	fd_ = -1;
+}
+
+/**
+ * \fn V4L2VideoDevice::driverName()
+ * \brief Retrieve the name of the V4L2 device driver
+ * \return The string containing the driver name
+ */
+
+/**
+ * \fn V4L2VideoDevice::deviceName()
+ * \brief Retrieve the name of the V4L2 device
+ * \return The string containing the device name
+ */
+
+/**
+ * \fn V4L2VideoDevice::busName()
+ * \brief Retrieve the location of the device in the system
+ * \return The string containing the device location
+ */
+
+/**
+ * \fn V4L2VideoDevice::deviceNode()
+ * \brief Retrieve the video device node path
+ * \return The video device device node path
+ */
+
+std::string V4L2VideoDevice::logPrefix() const
+{
+	return deviceNode_ + (V4L2_TYPE_IS_OUTPUT(bufferType_) ? "[out]" : "[cap]");
+}
+
+/**
+ * \brief Retrieve the image format set on the V4L2 device
+ * \param[out] format The image format applied on the device
+ * \return 0 on success or a negative error code otherwise
+ */
+int V4L2VideoDevice::getFormat(V4L2DeviceFormat *format)
+{
+	if (caps_.isMeta())
+		return getFormatMeta(format);
+	else if (caps_.isMultiplanar())
+		return getFormatMultiplane(format);
+	else
+		return getFormatSingleplane(format);
+}
+
+/**
+ * \brief Configure an image format on the V4L2 device
+ * \param[inout] format The image format to apply to the device
+ *
+ * Apply the supplied \a format to the device, and return the actually
+ * applied format parameters, as \ref V4L2VideoDevice::getFormat would do.
+ *
+ * \return 0 on success or a negative error code otherwise
+ */
+int V4L2VideoDevice::setFormat(V4L2DeviceFormat *format)
+{
+	if (caps_.isMeta())
+		return setFormatMeta(format);
+	else if (caps_.isMultiplanar())
+		return setFormatMultiplane(format);
+	else
+		return setFormatSingleplane(format);
+}
+
+int V4L2VideoDevice::getFormatMeta(V4L2DeviceFormat *format)
+{
+	struct v4l2_format v4l2Format = {};
+	struct v4l2_meta_format *pix = &v4l2Format.fmt.meta;
+	int ret;
+
+	v4l2Format.type = bufferType_;
+	ret = ioctl(fd_, VIDIOC_G_FMT, &v4l2Format);
+	if (ret) {
+		ret = -errno;
+		LOG(V4L2, Error) << "Unable to get format: " << strerror(-ret);
+		return ret;
+	}
+
+	format->size.width = 0;
+	format->size.height = 0;
+	format->fourcc = pix->dataformat;
+	format->planesCount = 1;
+	format->planes[0].bpl = pix->buffersize;
+	format->planes[0].size = pix->buffersize;
+
+	return 0;
+}
+
+int V4L2VideoDevice::setFormatMeta(V4L2DeviceFormat *format)
+{
+	struct v4l2_format v4l2Format = {};
+	struct v4l2_meta_format *pix = &v4l2Format.fmt.meta;
+	int ret;
+
+	v4l2Format.type = bufferType_;
+	pix->dataformat = format->fourcc;
+	pix->buffersize = format->planes[0].size;
+	ret = ioctl(fd_, VIDIOC_S_FMT, &v4l2Format);
+	if (ret) {
+		ret = -errno;
+		LOG(V4L2, Error) << "Unable to set format: " << strerror(-ret);
+		return ret;
+	}
+
+	/*
+	 * Return to caller the format actually applied on the device,
+	 * which might differ from the requested one.
+	 */
+	format->size.width = 0;
+	format->size.height = 0;
+	format->fourcc = format->fourcc;
+	format->planesCount = 1;
+	format->planes[0].bpl = pix->buffersize;
+	format->planes[0].size = pix->buffersize;
+
+	return 0;
+}
+
+int V4L2VideoDevice::getFormatMultiplane(V4L2DeviceFormat *format)
+{
+	struct v4l2_format v4l2Format = {};
+	struct v4l2_pix_format_mplane *pix = &v4l2Format.fmt.pix_mp;
+	int ret;
+
+	v4l2Format.type = bufferType_;
+	ret = ioctl(fd_, VIDIOC_G_FMT, &v4l2Format);
+	if (ret) {
+		ret = -errno;
+		LOG(V4L2, Error) << "Unable to get format: " << strerror(-ret);
+		return ret;
+	}
+
+	format->size.width = pix->width;
+	format->size.height = pix->height;
+	format->fourcc = pix->pixelformat;
+	format->planesCount = pix->num_planes;
+
+	for (unsigned int i = 0; i < format->planesCount; ++i) {
+		format->planes[i].bpl = pix->plane_fmt[i].bytesperline;
+		format->planes[i].size = pix->plane_fmt[i].sizeimage;
+	}
+
+	return 0;
+}
+
+int V4L2VideoDevice::setFormatMultiplane(V4L2DeviceFormat *format)
+{
+	struct v4l2_format v4l2Format = {};
+	struct v4l2_pix_format_mplane *pix = &v4l2Format.fmt.pix_mp;
+	int ret;
+
+	v4l2Format.type = bufferType_;
+	pix->width = format->size.width;
+	pix->height = format->size.height;
+	pix->pixelformat = format->fourcc;
+	pix->num_planes = format->planesCount;
+	pix->field = V4L2_FIELD_NONE;
+
+	for (unsigned int i = 0; i < pix->num_planes; ++i) {
+		pix->plane_fmt[i].bytesperline = format->planes[i].bpl;
+		pix->plane_fmt[i].sizeimage = format->planes[i].size;
+	}
+
+	ret = ioctl(fd_, VIDIOC_S_FMT, &v4l2Format);
+	if (ret) {
+		ret = -errno;
+		LOG(V4L2, Error) << "Unable to set format: " << strerror(-ret);
+		return ret;
+	}
+
+	/*
+	 * Return to caller the format actually applied on the device,
+	 * which might differ from the requested one.
+	 */
+	format->size.width = pix->width;
+	format->size.height = pix->height;
+	format->fourcc = pix->pixelformat;
+	format->planesCount = pix->num_planes;
+	for (unsigned int i = 0; i < format->planesCount; ++i) {
+		format->planes[i].bpl = pix->plane_fmt[i].bytesperline;
+		format->planes[i].size = pix->plane_fmt[i].sizeimage;
+	}
+
+	return 0;
+}
+
+int V4L2VideoDevice::getFormatSingleplane(V4L2DeviceFormat *format)
+{
+	struct v4l2_format v4l2Format = {};
+	struct v4l2_pix_format *pix = &v4l2Format.fmt.pix;
+	int ret;
+
+	v4l2Format.type = bufferType_;
+	ret = ioctl(fd_, VIDIOC_G_FMT, &v4l2Format);
+	if (ret) {
+		ret = -errno;
+		LOG(V4L2, Error) << "Unable to get format: " << strerror(-ret);
+		return ret;
+	}
+
+	format->size.width = pix->width;
+	format->size.height = pix->height;
+	format->fourcc = pix->pixelformat;
+	format->planesCount = 1;
+	format->planes[0].bpl = pix->bytesperline;
+	format->planes[0].size = pix->sizeimage;
+
+	return 0;
+}
+
+int V4L2VideoDevice::setFormatSingleplane(V4L2DeviceFormat *format)
+{
+	struct v4l2_format v4l2Format = {};
+	struct v4l2_pix_format *pix = &v4l2Format.fmt.pix;
+	int ret;
+
+	v4l2Format.type = bufferType_;
+	pix->width = format->size.width;
+	pix->height = format->size.height;
+	pix->pixelformat = format->fourcc;
+	pix->bytesperline = format->planes[0].bpl;
+	pix->field = V4L2_FIELD_NONE;
+	ret = ioctl(fd_, VIDIOC_S_FMT, &v4l2Format);
+	if (ret) {
+		ret = -errno;
+		LOG(V4L2, Error) << "Unable to set format: " << strerror(-ret);
+		return ret;
+	}
+
+	/*
+	 * Return to caller the format actually applied on the device,
+	 * which might differ from the requested one.
+	 */
+	format->size.width = pix->width;
+	format->size.height = pix->height;
+	format->fourcc = pix->pixelformat;
+	format->planesCount = 1;
+	format->planes[0].bpl = pix->bytesperline;
+	format->planes[0].size = pix->sizeimage;
+
+	return 0;
+}
+
+/**
+ * \brief Enumerate all pixel formats and frame sizes
+ *
+ * Enumerate all pixel formats and frame sizes supported by the video device.
+ *
+ * \return A list of the supported device formats
+ */
+ImageFormats V4L2VideoDevice::formats()
+{
+	ImageFormats formats;
+
+	for (unsigned int pixelformat : enumPixelformats()) {
+		std::vector<SizeRange> sizes = enumSizes(pixelformat);
+		if (sizes.empty())
+			return {};
+
+		if (formats.addFormat(pixelformat, sizes)) {
+			LOG(V4L2, Error)
+				<< "Could not add sizes for pixel format "
+				<< pixelformat;
+			return {};
+		}
+	}
+
+	return formats;
+}
+
+int V4L2VideoDevice::requestBuffers(unsigned int count)
+{
+	struct v4l2_requestbuffers rb = {};
+	int ret;
+
+	rb.count = count;
+	rb.type = bufferType_;
+	rb.memory = memoryType_;
+
+	ret = ioctl(fd_, VIDIOC_REQBUFS, &rb);
+	if (ret < 0) {
+		ret = -errno;
+		LOG(V4L2, Error)
+			<< "Unable to request " << count << " buffers: "
+			<< strerror(-ret);
+		return ret;
+	}
+
+	LOG(V4L2, Debug) << rb.count << " buffers requested.";
+
+	return rb.count;
+}
+
+/**
+ * \brief Request buffers to be allocated from the device and stored in the
+ *  buffer pool provided.
+ * \param[out] pool BufferPool to populate with buffers
+ * \return 0 on success or a negative error code otherwise
+ */
+int V4L2VideoDevice::exportBuffers(BufferPool *pool)
+{
+	unsigned int allocatedBuffers;
+	unsigned int i;
+	int ret;
+
+	memoryType_ = V4L2_MEMORY_MMAP;
+
+	ret = requestBuffers(pool->count());
+	if (ret < 0)
+		return ret;
+
+	allocatedBuffers = ret;
+	if (allocatedBuffers < pool->count()) {
+		LOG(V4L2, Error)
+			<< "Not enough buffers provided by V4L2VideoDevice";
+		requestBuffers(0);
+		return -ENOMEM;
+	}
+
+	/* Map the buffers. */
+	for (i = 0; i < pool->count(); ++i) {
+		struct v4l2_plane planes[VIDEO_MAX_PLANES] = {};
+		struct v4l2_buffer buf = {};
+		Buffer &buffer = pool->buffers()[i];
+
+		buf.index = i;
+		buf.type = bufferType_;
+		buf.memory = memoryType_;
+		buf.length = VIDEO_MAX_PLANES;
+		buf.m.planes = planes;
+
+		ret = ioctl(fd_, VIDIOC_QUERYBUF, &buf);
+		if (ret < 0) {
+			ret = -errno;
+			LOG(V4L2, Error)
+				<< "Unable to query buffer " << i << ": "
+				<< strerror(-ret);
+			break;
+		}
+
+		if (V4L2_TYPE_IS_MULTIPLANAR(buf.type)) {
+			for (unsigned int p = 0; p < buf.length; ++p) {
+				ret = createPlane(&buffer, p,
+						  buf.m.planes[p].length);
+				if (ret)
+					break;
+			}
+		} else {
+			ret = createPlane(&buffer, 0, buf.length);
+		}
+
+		if (ret) {
+			LOG(V4L2, Error) << "Failed to create plane";
+			break;
+		}
+	}
+
+	if (ret) {
+		requestBuffers(0);
+		pool->destroyBuffers();
+		return ret;
+	}
+
+	bufferPool_ = pool;
+
+	return 0;
+}
+
+int V4L2VideoDevice::createPlane(Buffer *buffer, unsigned int planeIndex,
+				 unsigned int length)
+{
+	struct v4l2_exportbuffer expbuf = {};
+	int ret;
+
+	LOG(V4L2, Debug)
+		<< "Buffer " << buffer->index()
+		<< " plane " << planeIndex
+		<< ": length=" << length;
+
+	expbuf.type = bufferType_;
+	expbuf.index = buffer->index();
+	expbuf.plane = planeIndex;
+	expbuf.flags = O_RDWR;
+
+	ret = ioctl(fd_, VIDIOC_EXPBUF, &expbuf);
+	if (ret < 0) {
+		ret = -errno;
+		LOG(V4L2, Error)
+			<< "Failed to export buffer: " << strerror(-ret);
+		return ret;
+	}
+
+	buffer->planes().emplace_back();
+	Plane &plane = buffer->planes().back();
+	plane.setDmabuf(expbuf.fd, length);
+	::close(expbuf.fd);
+
+	return 0;
+}
+
+std::vector<unsigned int> V4L2VideoDevice::enumPixelformats()
+{
+	std::vector<unsigned int> formats;
+	int ret;
+
+	for (unsigned int index = 0; ; index++) {
+		struct v4l2_fmtdesc pixelformatEnum = {};
+		pixelformatEnum.index = index;
+		pixelformatEnum.type = bufferType_;
+
+		ret = ioctl(fd_, VIDIOC_ENUM_FMT, &pixelformatEnum);
+		if (ret)
+			break;
+
+		formats.push_back(pixelformatEnum.pixelformat);
+	}
+
+	if (ret && errno != EINVAL) {
+		ret = -errno;
+		LOG(V4L2, Error)
+			<< "Unable to enumerate pixel formats: "
+			<< strerror(-ret);
+		return {};
+	}
+
+	return formats;
+}
+
+std::vector<SizeRange> V4L2VideoDevice::enumSizes(unsigned int pixelFormat)
+{
+	std::vector<SizeRange> sizes;
+	int ret;
+
+	for (unsigned int index = 0;; index++) {
+		struct v4l2_frmsizeenum frameSize = {};
+		frameSize.index = index;
+		frameSize.pixel_format = pixelFormat;
+
+		ret = ioctl(fd_, VIDIOC_ENUM_FRAMESIZES, &frameSize);
+		if (ret)
+			break;
+
+		if (index != 0 &&
+		    frameSize.type != V4L2_FRMSIZE_TYPE_DISCRETE) {
+			LOG(V4L2, Error)
+				<< "Non-zero index for non discrete type";
+			return {};
+		}
+
+		switch (frameSize.type) {
+		case V4L2_FRMSIZE_TYPE_DISCRETE:
+			sizes.emplace_back(frameSize.discrete.width,
+					   frameSize.discrete.height);
+			break;
+		case V4L2_FRMSIZE_TYPE_CONTINUOUS:
+			sizes.emplace_back(frameSize.stepwise.min_width,
+					   frameSize.stepwise.min_height,
+					   frameSize.stepwise.max_width,
+					   frameSize.stepwise.max_height);
+			break;
+		case V4L2_FRMSIZE_TYPE_STEPWISE:
+			sizes.emplace_back(frameSize.stepwise.min_width,
+					   frameSize.stepwise.min_height,
+					   frameSize.stepwise.max_width,
+					   frameSize.stepwise.max_height,
+					   frameSize.stepwise.step_width,
+					   frameSize.stepwise.step_height);
+			break;
+		default:
+			LOG(V4L2, Error)
+				<< "Unknown VIDIOC_ENUM_FRAMESIZES type "
+				<< frameSize.type;
+			return {};
+		}
+	}
+
+	if (ret && errno != EINVAL) {
+		ret = -errno;
+		LOG(V4L2, Error)
+			<< "Unable to enumerate frame sizes: "
+			<< strerror(-ret);
+		return {};
+	}
+
+	return sizes;
+}
+
+/**
+ * \brief Import the externally allocated \a pool of buffers
+ * \param[in] pool BufferPool of buffers to import
+ * \return 0 on success or a negative error code otherwise
+ */
+int V4L2VideoDevice::importBuffers(BufferPool *pool)
+{
+	unsigned int allocatedBuffers;
+	int ret;
+
+	memoryType_ = V4L2_MEMORY_DMABUF;
+
+	ret = requestBuffers(pool->count());
+	if (ret < 0)
+		return ret;
+
+	allocatedBuffers = ret;
+	if (allocatedBuffers < pool->count()) {
+		LOG(V4L2, Error)
+			<< "Not enough buffers provided by V4L2VideoDevice";
+		requestBuffers(0);
+		return -ENOMEM;
+	}
+
+	LOG(V4L2, Debug) << "provided pool of " << pool->count() << " buffers";
+	bufferPool_ = pool;
+
+	return 0;
+}
+
+/**
+ * \brief Release all internally allocated buffers
+ */
+int V4L2VideoDevice::releaseBuffers()
+{
+	LOG(V4L2, Debug) << "Releasing bufferPool";
+
+	bufferPool_ = nullptr;
+
+	return requestBuffers(0);
+}
+
+/**
+ * \brief Queue a buffer into the device
+ * \param[in] buffer The buffer to be queued
+ *
+ * For capture devices the \a buffer will be filled with data by the device.
+ * For output 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.
+ *
+ * \return 0 on success or a negative error code otherwise
+ */
+int V4L2VideoDevice::queueBuffer(Buffer *buffer)
+{
+	struct v4l2_buffer buf = {};
+	struct v4l2_plane planes[VIDEO_MAX_PLANES] = {};
+	int ret;
+
+	buf.index = buffer->index();
+	buf.type = bufferType_;
+	buf.memory = memoryType_;
+	buf.field = V4L2_FIELD_NONE;
+
+	bool multiPlanar = V4L2_TYPE_IS_MULTIPLANAR(buf.type);
+
+	if (buf.memory == V4L2_MEMORY_DMABUF) {
+		if (multiPlanar) {
+			for (unsigned int p = 0;
+			     p < buffer->planes().size();
+			     p++)
+				planes[p].m.fd = buffer->planes()[p].dmabuf();
+		} else {
+			buf.m.fd = buffer->planes()[0].dmabuf();
+		}
+	}
+
+	if (multiPlanar) {
+		buf.length = buffer->planes().size();
+		buf.m.planes = planes;
+	}
+
+	if (V4L2_TYPE_IS_OUTPUT(bufferType_)) {
+		buf.bytesused = buffer->bytesused_;
+		buf.sequence = buffer->sequence_;
+		buf.timestamp.tv_sec = buffer->timestamp_ / 1000000000;
+		buf.timestamp.tv_usec = (buffer->timestamp_ / 1000) % 1000000;
+	}
+
+	LOG(V4L2, Debug) << "Queueing buffer " << buf.index;
+
+	ret = ioctl(fd_, VIDIOC_QBUF, &buf);
+	if (ret < 0) {
+		ret = -errno;
+		LOG(V4L2, Error)
+			<< "Failed to queue buffer " << buf.index << ": "
+			<< strerror(-ret);
+		return ret;
+	}
+
+	if (queuedBuffersCount_++ == 0)
+		fdEvent_->setEnabled(true);
+
+	return 0;
+}
+
+/**
+ * \brief Dequeue the next available buffer from the device
+ *
+ * This method dequeues the next available buffer from the device. If no buffer
+ * is available to be dequeued it will return nullptr immediately.
+ *
+ * \return A pointer to the dequeued buffer on success, or nullptr otherwise
+ */
+Buffer *V4L2VideoDevice::dequeueBuffer()
+{
+	struct v4l2_buffer buf = {};
+	struct v4l2_plane planes[VIDEO_MAX_PLANES] = {};
+	int ret;
+
+	buf.type = bufferType_;
+	buf.memory = memoryType_;
+
+	if (V4L2_TYPE_IS_MULTIPLANAR(buf.type)) {
+		buf.length = VIDEO_MAX_PLANES;
+		buf.m.planes = planes;
+	}
+
+	ret = ioctl(fd_, VIDIOC_DQBUF, &buf);
+	if (ret < 0) {
+		ret = -errno;
+		LOG(V4L2, Error)
+			<< "Failed to dequeue buffer: " << strerror(-ret);
+		return nullptr;
+	}
+
+	ASSERT(buf.index < bufferPool_->count());
+
+	if (--queuedBuffersCount_ == 0)
+		fdEvent_->setEnabled(false);
+
+	Buffer *buffer = &bufferPool_->buffers()[buf.index];
+
+	buffer->bytesused_ = buf.bytesused;
+	buffer->timestamp_ = buf.timestamp.tv_sec * 1000000000ULL
+			   + buf.timestamp.tv_usec * 1000ULL;
+	buffer->sequence_ = buf.sequence;
+	buffer->status_ = buf.flags & V4L2_BUF_FLAG_ERROR
+			? Buffer::BufferError : Buffer::BufferSuccess;
+
+	return buffer;
+}
+
+/**
+ * \brief Slot to handle completed buffer events from the V4L2 device
+ * \param[in] notifier The event notifier
+ *
+ * When this slot is called, a Buffer has become available from the device, and
+ * will be emitted through the bufferReady Signal.
+ *
+ * For Capture devices the Buffer will contain valid data.
+ * For Output devices the Buffer can be considered empty.
+ */
+void V4L2VideoDevice::bufferAvailable(EventNotifier *notifier)
+{
+	Buffer *buffer = dequeueBuffer();
+	if (!buffer)
+		return;
+
+	LOG(V4L2, Debug) << "Buffer " << buffer->index() << " is available";
+
+	/* Notify anyone listening to the device. */
+	bufferReady.emit(buffer);
+}
+
+/**
+ * \var V4L2VideoDevice::bufferReady
+ * \brief A Signal emitted when a buffer completes
+ */
+
+/**
+ * \brief Start the video stream
+ * \return 0 on success or a negative error code otherwise
+ */
+int V4L2VideoDevice::streamOn()
+{
+	int ret;
+
+	ret = ioctl(fd_, VIDIOC_STREAMON, &bufferType_);
+	if (ret < 0) {
+		ret = -errno;
+		LOG(V4L2, Error)
+			<< "Failed to start streaming: " << strerror(-ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * \brief Stop the video stream
+ *
+ * Buffers that are still queued when the video stream is stopped are
+ * implicitly dequeued, but no bufferReady signal is emitted for them.
+ *
+ * \return 0 on success or a negative error code otherwise
+ */
+int V4L2VideoDevice::streamOff()
+{
+	int ret;
+
+	ret = ioctl(fd_, VIDIOC_STREAMOFF, &bufferType_);
+	if (ret < 0) {
+		ret = -errno;
+		LOG(V4L2, Error)
+			<< "Failed to stop streaming: " << strerror(-ret);
+		return ret;
+	}
+
+	queuedBuffersCount_ = 0;
+	fdEvent_->setEnabled(false);
+
+	return 0;
+}
+
+/**
+ * \brief Create a new video device instance from \a entity in media device
+ * \a media
+ * \param[in] media The media device where the entity is registered
+ * \param[in] entity The media entity name
+ *
+ * Releasing memory of the newly created instance is responsibility of the
+ * caller of this function.
+ *
+ * \return A newly created V4L2VideoDevice on success, nullptr otherwise
+ */
+V4L2VideoDevice *V4L2VideoDevice::fromEntityName(const MediaDevice *media,
+						 const std::string &entity)
+{
+	MediaEntity *mediaEntity = media->getEntityByName(entity);
+	if (!mediaEntity)
+		return nullptr;
+
+	return new V4L2VideoDevice(mediaEntity);
+}
+
+} /* namespace libcamera */