/* SPDX-License-Identifier: LGPL-2.1-or-later */ /* * Copyright (C) 2021, Google Inc. * * generic_camera_buffer.cpp - Generic Android frame buffer backend */ #include "../camera_buffer.h" #include #include #include #include "libcamera/internal/formats.h" #include "libcamera/internal/mapped_framebuffer.h" using namespace libcamera; LOG_DECLARE_CATEGORY(HAL) class CameraBuffer::Private : public Extensible::Private, public MappedBuffer { LIBCAMERA_DECLARE_PUBLIC(CameraBuffer) public: Private(CameraBuffer *cameraBuffer, buffer_handle_t camera3Buffer, PixelFormat pixelFormat, const Size &size, int flags); ~Private(); unsigned int numPlanes() const; Span plane(unsigned int plane); unsigned int stride(unsigned int plane) const; unsigned int offset(unsigned int plane) const; unsigned int size(unsigned int plane) const; size_t jpegBufferSize(size_t maxJpegBufferSize) const; private: struct PlaneInfo { unsigned int stride; unsigned int offset; unsigned int size; }; void map(); int fd_; int flags_; off_t bufferLength_; bool mapped_; std::vector planeInfo_; }; CameraBuffer::Private::Private([[maybe_unused]] CameraBuffer *cameraBuffer, buffer_handle_t camera3Buffer, PixelFormat pixelFormat, const Size &size, int flags) : fd_(-1), flags_(flags), bufferLength_(-1), mapped_(false) { error_ = 0; const auto &info = PixelFormatInfo::info(pixelFormat); if (!info.isValid()) { error_ = -EINVAL; LOG(HAL, Error) << "Invalid pixel format: " << pixelFormat.toString(); return; } /* * As Android doesn't offer an API to query buffer layouts, assume for * now that the buffer is backed by a single dmabuf, with planes being * stored contiguously. */ for (int i = 0; i < camera3Buffer->numFds; i++) { if (camera3Buffer->data[i] == -1 || camera3Buffer->data[i] == fd_) continue; if (fd_ != -1) { error_ = -EINVAL; LOG(HAL, Error) << "Discontiguous planes are not supported"; return; } fd_ = camera3Buffer->data[i]; } if (fd_ == -1) { error_ = -EINVAL; LOG(HAL, Error) << "No valid file descriptor"; return; } bufferLength_ = lseek(fd_, 0, SEEK_END); if (bufferLength_ < 0) { error_ = -errno; LOG(HAL, Error) << "Failed to get buffer length"; return; } const unsigned int numPlanes = info.numPlanes(); planeInfo_.resize(numPlanes); unsigned int offset = 0; for (unsigned int i = 0; i < numPlanes; ++i) { const unsigned int planeSize = info.planeSize(size, i); planeInfo_[i].stride = info.stride(size.width, i, 1u); planeInfo_[i].offset = offset; planeInfo_[i].size = planeSize; if (bufferLength_ < offset + planeSize) { LOG(HAL, Error) << "Plane " << i << " is out of buffer:" << " plane offset=" << offset << ", plane size=" << planeSize << ", buffer length=" << bufferLength_; return; } offset += planeSize; } } CameraBuffer::Private::~Private() { } unsigned int CameraBuffer::Private::numPlanes() const { return planeInfo_.size(); } Span CameraBuffer::Private::plane(unsigned int plane) { if (!mapped_) map(); if (!mapped_) return {}; return planes_[plane]; } unsigned int CameraBuffer::Private::stride(unsigned int plane) const { if (plane >= planeInfo_.size()) return 0; return planeInfo_[plane].stride; } unsigned int CameraBuffer::Private::offset(unsigned int plane) const { if (plane >= planeInfo_.size()) return 0; return planeInfo_[plane].offset; } unsigned int CameraBuffer::Private::size(unsigned int plane) const { if (plane >= planeInfo_.size()) return 0; return planeInfo_[plane].size; } size_t CameraBuffer::Private::jpegBufferSize(size_t maxJpegBufferSize) const { ASSERT(bufferLength_ >= 0); return std::min(bufferLength_, maxJpegBufferSize); } void CameraBuffer::Private::map() { ASSERT(fd_ != -1); ASSERT(bufferLength_ >= 0); void *address = mmap(nullptr, bufferLength_, flags_, MAP_SHARED, fd_, 0); if (address == MAP_FAILED) { error_ = -errno; LOG(HAL, Error) << "Failed to mmap plane"; return; } maps_.emplace_back(static_cast(address), bufferLength_); planes_.reserve(planeInfo_.size()); for (const auto &info : planeInfo_) { planes_.emplace_back( static_cast(address) + info.offset, info.size); } mapped_ = true; } PUBLIC_CAMERA_BUFFER_IMPLEMENTATION '#n21'>21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * V4L2 Video Device
 */

#include "libcamera/internal/v4l2_videodevice.h"

#include <algorithm>
#include <array>
#include <fcntl.h>
#include <sstream>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <unistd.h>
#include <vector>

#include <linux/version.h>

#include <libcamera/base/event_notifier.h>
#include <libcamera/base/log.h>
#include <libcamera/base/shared_fd.h>
#include <libcamera/base/unique_fd.h>
#include <libcamera/base/utils.h>

#include "libcamera/internal/formats.h"
#include "libcamera/internal/framebuffer.h"
#include "libcamera/internal/media_device.h"
#include "libcamera/internal/media_object.h"

/**
 * \file v4l2_videodevice.h
 * \brief V4L2 Video Device
 */

namespace libcamera {

LOG_DECLARE_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 video device card name
 * \return The string containing the video device name
 */

/**
 * \fn V4L2Capability::bus_info()
 * \brief Retrieve the location of the video device in the system
 * \return The string containing the video device location
 */

/**
 * \fn V4L2Capability::device_caps()
 * \brief Retrieve the capabilities of the video device
 * \return The video device specific capabilities if V4L2_CAP_DEVICE_CAPS is
 * set or driver capabilities otherwise
 */

/**
 * \fn V4L2Capability::isMultiplanar()
 * \brief Identify if the video device implements the V4L2 multiplanar APIs
 * \return True if the video device supports multiplanar APIs
 */

/**
 * \fn V4L2Capability::isCapture()
 * \brief Identify if the video device captures data
 * \return True if the video device can capture data
 */

/**
 * \fn V4L2Capability::isOutput()
 * \brief Identify if the video device outputs data
 * \return True if the video device can output data
 */

/**
 * \fn V4L2Capability::isVideo()
 * \brief Identify if the video device captures or outputs images
 * \return True if the video device can capture or output images
 */

/**
 * \fn V4L2Capability::isM2M()
 * \brief Identify if the device is a Memory-to-Memory device
 * \return True if the device can capture and output images using the M2M API
 */

/**
 * \fn V4L2Capability::isMeta()
 * \brief Identify if the video device captures or outputs image meta-data
 * \return True if the video device can capture or output image meta-data
 */

/**
 * \fn V4L2Capability::isVideoCapture()
 * \brief Identify if the video device captures images
 * \return True if the video device can capture images
 */

/**
 * \fn V4L2Capability::isVideoOutput()
 * \brief Identify if the video device outputs images
 * \return True if the video device can output images
 */

/**
 * \fn V4L2Capability::isMetaCapture()
 * \brief Identify if the video device captures image meta-data
 * \return True if the video device can capture image meta-data
 */

/**
 * \fn V4L2Capability::isMetaOutput()
 * \brief Identify if the video device outputs image meta-data
 * \return True if the video device can output image meta-data
 */

/**
 * \fn V4L2Capability::hasStreaming()
 * \brief Determine if the video device can perform Streaming I/O
 * \return True if the video device provides Streaming I/O IOCTLs
 */

/**
 * \fn V4L2Capability::hasMediaController()
 * \brief Determine if the video device uses Media Controller to configure I/O
 * \return True if the video device is controlled by a Media Controller device
 */

/**
 * \class V4L2BufferCache
 * \brief Hot cache of associations between V4L2 buffer indexes and FrameBuffer
 *
 * When importing buffers, V4L2 performs lazy mapping of dmabuf instances at
 * VIDIOC_QBUF (or VIDIOC_PREPARE_BUF) time and keeps the mapping associated
 * with the V4L2 buffer, as identified by its index. If the same V4L2 buffer is
 * then reused and queued with different dmabufs, the old dmabufs will be
 * unmapped and the new ones mapped. To keep this process efficient, it is
 * crucial to consistently use the same V4L2 buffer for given dmabufs through
 * the whole duration of a capture cycle.
 *
 * The V4L2BufferCache class keeps a map of previous dmabufs to V4L2 buffer
 * index associations to help selecting V4L2 buffers. It tracks, for every
 * entry, if the V4L2 buffer is in use, and offers lookup of the best free V4L2
 * buffer for a set of dmabufs.
 */

/**
 * \brief Create an empty cache with \a numEntries entries
 * \param[in] numEntries Number of entries to reserve in the cache
 *
 * Create a cache with \a numEntries entries all marked as unused. The entries
 * will be populated as the cache is used. This is typically used to implement
 * buffer import, with buffers added to the cache as they are queued.
 */
V4L2BufferCache::V4L2BufferCache(unsigned int numEntries)
	: lastUsedCounter_(1), missCounter_(0)
{
	cache_.resize(numEntries);
}

/**
 * \brief Create a pre-populated cache
 * \param[in] buffers Array of buffers to pre-populated with
 *
 * Create a cache pre-populated with \a buffers. This is typically used to
 * implement buffer export, with all buffers added to the cache when they are
 * allocated.
 */
V4L2BufferCache::V4L2BufferCache(const std::vector<std::unique_ptr<FrameBuffer>> &buffers)
	: lastUsedCounter_(1), missCounter_(0)
{
	for (const std::unique_ptr<FrameBuffer> &buffer : buffers)
		cache_.emplace_back(true,
				    lastUsedCounter_.fetch_add(1, std::memory_order_acq_rel),
				    *buffer.get());
}

V4L2BufferCache::~V4L2BufferCache()
{
	if (missCounter_ > cache_.size())
		LOG(V4L2, Debug) << "Cache misses: " << missCounter_;
}

/**
 * \brief Check if all the entries in the cache are unused
 */
bool V4L2BufferCache::isEmpty() const
{
	for (auto const &entry : cache_) {
		if (!entry.free_)
			return false;
	}

	return true;
}

/**
 * \brief Find the best V4L2 buffer for a FrameBuffer
 * \param[in] buffer The FrameBuffer
 *
 * Find the best V4L2 buffer index to be used for the FrameBuffer \a buffer
 * based on previous mappings of frame buffers to V4L2 buffers. If a free V4L2
 * buffer previously used with the same dmabufs as \a buffer is found in the
 * cache, return its index. Otherwise return the index of the first free V4L2
 * buffer and record its association with the dmabufs of \a buffer.
 *
 * \return The index of the best V4L2 buffer, or -ENOENT if no free V4L2 buffer
 * is available
 */
int V4L2BufferCache::get(const FrameBuffer &buffer)
{
	bool hit = false;
	int use = -1;
	uint64_t oldest = UINT64_MAX;

	for (unsigned int index = 0; index < cache_.size(); index++) {
		const Entry &entry = cache_[index];

		if (!entry.free_)
			continue;

		/* Try to find a cache hit by comparing the planes. */
		if (entry == buffer) {
			hit = true;
			use = index;
			break;
		}

		if (entry.lastUsed_ < oldest) {
			use = index;
			oldest = entry.lastUsed_;
		}
	}

	if (!hit)
		missCounter_++;

	if (use < 0)
		return -ENOENT;

	cache_[use] = Entry(false,
			    lastUsedCounter_.fetch_add(1, std::memory_order_acq_rel),
			    buffer);

	return use;
}

/**
 * \brief Mark buffer \a index as free in the cache
 * \param[in] index The V4L2 buffer index
 */
void V4L2BufferCache::put(unsigned int index)
{
	ASSERT(index < cache_.size());
	cache_[index].free_ = true;
}

V4L2BufferCache::Entry::Entry()
	: free_(true), lastUsed_(0)
{
}

V4L2BufferCache::Entry::Entry(bool free, uint64_t lastUsed, const FrameBuffer &buffer)
	: free_(free), lastUsed_(lastUsed)
{
	for (const FrameBuffer::Plane &plane : buffer.planes())
		planes_.emplace_back(plane);
}

bool V4L2BufferCache::Entry::operator==(const FrameBuffer &buffer) const
{
	const std::vector<FrameBuffer::Plane> &planes = buffer.planes();

	if (planes_.size() != planes.size())
		return false;

	for (unsigned int i = 0; i < planes.size(); i++)
		if (planes_[i].fd != planes[i].fd.get() ||
		    planes_[i].length != planes[i].length)
			return false;
	return true;
}

/**
 * \class V4L2DeviceFormat
 * \brief The V4L2 video 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 video 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 video 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 video
 * 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.
 */

/**
 * \struct V4L2DeviceFormat::Plane
 * \brief Per-plane memory size information
 * \var V4L2DeviceFormat::Plane::size
 * \brief The plane total memory size (in bytes)
 * \var V4L2DeviceFormat::Plane::bpl
 * \brief The plane line stride (in bytes)
 */

/**
 * \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::colorSpace
 * \brief The color space of the pixels
 *
 * The color space of the image. When setting the format this may be
 * unset, in which case the driver gets to use its default color space.
 * After being set, this value should contain the color space that
 * was actually used. If this value is unset, then the color space chosen
 * by the driver could not be represented by the ColorSpace class (and
 * should probably be added).
 *
 * It is up to the pipeline handler or application to check if the
 * resulting color space is acceptable.
 */

/**
 * \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 << *this;

	return ss.str();
}

/**
 * \brief Insert a text representation of a V4L2DeviceFormat into an output
 * stream
 * \param[in] out The output stream
 * \param[in] f The V4L2DeviceFormat
 * \return The output stream \a out
 */
std::ostream &operator<<(std::ostream &out, const V4L2DeviceFormat &f)
{
	out << f.size << "-" << f.fourcc;
	return out;
}

/**
 * \class V4L2VideoDevice
 * \brief V4L2VideoDevice object and API
 *
 * The V4L2VideoDevice class models an instance of a V4L2 video device.
 * 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 video device capabilities are validated when the device is opened and the
 * device is rejected if it is not a suitable V4L2 capture or output video
 * device, or if the video 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 supports the V4L2 MMAP and DMABUF memory types:
 *
 * - The allocateBuffers() function wraps buffer allocation with the V4L2 MMAP
 *   memory type. It requests buffers from the driver, allocating the
 *   corresponding memory, and exports them as a set of FrameBuffer objects.
 *   Upon successful return the driver's internal buffer management is
 *   initialized in MMAP mode, and the video device is ready to accept
 *   queueBuffer() calls.
 *
 *   This is the most traditional V4L2 buffer management, and is mostly useful
 *   to support internal buffer pools in pipeline handlers, either for CPU
 *   consumption (such as statistics or parameters pools), or for internal
 *   image buffers shared between devices.
 *
 * - The exportBuffers() function operates similarly to allocateBuffers(), but
 *   leaves the driver's internal buffer management uninitialized. It uses the
 *   V4L2 buffer orphaning support to allocate buffers with the MMAP method,
 *   export them as a set of FrameBuffer objects, and reset the driver's
 *   internal buffer management. The video device shall be initialized with
 *   importBuffers() or allocateBuffers() before it can accept queueBuffer()
 *   calls. The exported buffers are directly usable with any V4L2 video device
 *   in DMABUF mode, or with other dmabuf importers.
 *
 *   This method is mostly useful to implement buffer allocation helpers or to
 *   allocate ancillary buffers, when a V4L2 video device is used in DMABUF
 *   mode but no other source of buffers is available. An example use case
 *   would be allocation of scratch buffers to be used in case of buffer
 *   underruns on a video device that is otherwise supplied with external
 *   buffers.
 *
 * - The importBuffers() function initializes the driver's buffer management to
 *   import buffers in DMABUF mode. It requests buffers from the driver, but
 *   doesn't allocate memory. Upon successful return, the video device is ready
 *   to accept queueBuffer() calls. The buffers to be imported are provided to
 *   queueBuffer(), and may be supplied externally, or come from a previous
 *   exportBuffers() call.
 *
 *   This is the usual buffers initialization method for video devices whose
 *   buffers are exposed outside of libcamera. It is also typically used on one
 *   of the two video device that participate in buffer sharing inside
 *   pipelines, the other video device typically using allocateBuffers().
 *
 * - The releaseBuffers() function resets the driver's internal buffer
 *   management that was initialized by a previous call to allocateBuffers() or
 *   importBuffers(). Any memory allocated by allocateBuffers() is freed.
 *   Buffer exported by exportBuffers() are not affected by this function.
 *
 * 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.
 *
 * \context This class is \threadbound.
 */

/**
 * \typedef V4L2VideoDevice::Formats
 * \brief A map of supported V4L2 pixel formats to frame sizes
 */

/**
 * \brief Construct a V4L2VideoDevice
 * \param[in] deviceNode The file-system path to the video device node
 */
V4L2VideoDevice::V4L2VideoDevice(const std::string &deviceNode)
	: V4L2Device(deviceNode), formatInfo_(nullptr), cache_(nullptr),
	  fdBufferNotifier_(nullptr), state_(State::Stopped),
	  watchdogDuration_(0.0)
{
	/*
	 * We default to an MMAP based CAPTURE video 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 video device from
 *
 * Construct a V4L2VideoDevice from a MediaEntity's device node path.
 */
V4L2VideoDevice::V4L2VideoDevice(const MediaEntity *entity)
	: V4L2VideoDevice(entity->deviceNode())
{
	watchdog_.timeout.connect(this, &V4L2VideoDevice::watchdogExpired);
}

V4L2VideoDevice::~V4L2VideoDevice()
{
	close();
}

/**
 * \brief Open the V4L2 video device node and query its capabilities
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::open()
{
	int ret;

	ret = V4L2Device::open(O_RDWR | O_NONBLOCK);
	if (ret < 0)
		return ret;

	ret = ioctl(VIDIOC_QUERYCAP, &caps_);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Failed to query device capabilities: "
			<< strerror(-ret);
		return ret;
	}

	if (caps_.version < KERNEL_VERSION(5, 0, 0)) {
		LOG(V4L2, Error)
			<< "V4L2 API v" << (caps_.version >> 16)
			<< "." << ((caps_.version >> 8) & 0xff)
			<< "." << (caps_.version & 0xff)
			<< " too old, v5.0.0 or later is required";
		return -EINVAL;
	}

	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 video
	 * devices (POLLIN), and write notifications for OUTPUT video devices
	 * (POLLOUT).
	 */
	EventNotifier::Type notifierType;

	if (caps_.isVideoCapture()) {
		notifierType = EventNotifier::Read;
		bufferType_ = caps_.isMultiplanar()
			    ? V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
			    : V4L2_BUF_TYPE_VIDEO_CAPTURE;
	} else if (caps_.isVideoOutput()) {
		notifierType = EventNotifier::Write;
		bufferType_ = caps_.isMultiplanar()
			    ? V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE
			    : V4L2_BUF_TYPE_VIDEO_OUTPUT;
	} else if (caps_.isMetaCapture()) {
		notifierType = EventNotifier::Read;
		bufferType_ = V4L2_BUF_TYPE_META_CAPTURE;
	} else if (caps_.isMetaOutput()) {
		notifierType = EventNotifier::Write;
		bufferType_ = V4L2_BUF_TYPE_META_OUTPUT;
	} else {
		LOG(V4L2, Error) << "Device is not a supported type";
		return -EINVAL;
	}

	fdBufferNotifier_ = new EventNotifier(fd(), notifierType);
	fdBufferNotifier_->activated.connect(this, &V4L2VideoDevice::bufferAvailable);
	fdBufferNotifier_->setEnabled(false);

	LOG(V4L2, Debug)
		<< "Opened device " << caps_.bus_info() << ": "
		<< caps_.driver() << ": " << caps_.card();

	ret = initFormats();
	if (ret)
		return ret;

	return 0;
}

/**
 * \brief Open a V4L2 video device from an opened file handle and query its
 * capabilities
 * \param[in] handle The file descriptor to set
 * \param[in] type The device type to operate on
 *
 * This function opens a video device from the existing file descriptor \a
 * handle. Like open(), this function queries the capabilities of the device,
 * but handles it according to the given device \a type instead of determining
 * its type from the capabilities. This can be used to force a given device type
 * for memory-to-memory devices.
 *
 * The file descriptor \a handle is duplicated, no reference to the original
 * handle is kept.
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::open(SharedFD handle, enum v4l2_buf_type type)
{
	int ret;

	UniqueFD newFd = handle.dup();
	if (!newFd.isValid()) {
		ret = -errno;
		LOG(V4L2, Error) << "Failed to duplicate file handle: "
				 << strerror(-ret);
		return ret;
	}

	ret = V4L2Device::setFd(std::move(newFd));
	if (ret < 0) {
		LOG(V4L2, Error) << "Failed to set file handle: "
				 << strerror(-ret);
		return ret;
	}

	ret = ioctl(VIDIOC_QUERYCAP, &caps_);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Failed to query device capabilities: "
			<< strerror(-ret);
		return ret;
	}

	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 video
	 * devices (POLLIN), and write notifications for OUTPUT video devices
	 * (POLLOUT).
	 */
	EventNotifier::Type notifierType;

	switch (type) {
	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
		notifierType = EventNotifier::Write;
		bufferType_ = caps_.isMultiplanar()
			    ? V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE
			    : V4L2_BUF_TYPE_VIDEO_OUTPUT;
		break;
	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
		notifierType = EventNotifier::Read;
		bufferType_ = caps_.isMultiplanar()
			    ? V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
			    : V4L2_BUF_TYPE_VIDEO_CAPTURE;
		break;
	default:
		LOG(V4L2, Error) << "Unsupported buffer type";
		return -EINVAL;
	}

	fdBufferNotifier_ = new EventNotifier(fd(), notifierType);
	fdBufferNotifier_->activated.connect(this, &V4L2VideoDevice::bufferAvailable);
	fdBufferNotifier_->setEnabled(false);

	LOG(V4L2, Debug)
		<< "Opened device " << caps_.bus_info() << ": "
		<< caps_.driver() << ": " << caps_.card();

	ret = initFormats();
	if (ret)
		return ret;

	return 0;
}

int V4L2VideoDevice::initFormats()
{
	const std::vector<V4L2PixelFormat> &deviceFormats = enumPixelformats(0);
	if (deviceFormats.empty()) {
		LOG(V4L2, Error) << "Failed to initialize device formats";
		return -EINVAL;
	}

	pixelFormats_ = { deviceFormats.begin(), deviceFormats.end() };

	int ret = getFormat(&format_);
	if (ret) {
		LOG(V4L2, Error) << "Failed to get format";
		return ret;
	}

	formatInfo_ = &PixelFormatInfo::info(format_.fourcc);

	return 0;
}

/**
 * \brief Close the video device, releasing any resources acquired by open()
 */
void V4L2VideoDevice::close()
{
	if (!isOpen())
		return;

	releaseBuffers();
	delete fdBufferNotifier_;

	formatInfo_ = nullptr;

	V4L2Device::close();
}

/**
 * \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 video 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::caps()
 * \brief Retrieve the device V4L2 capabilities
 * \return The device V4L2 capabilities
 */

std::string V4L2VideoDevice::logPrefix() const
{
	return deviceNode() + "[" + std::to_string(fd()) +
		(V4L2_TYPE_IS_OUTPUT(bufferType_) ? ":out]" : ":cap]");
}

/**
 * \brief Retrieve the image format set on the V4L2 video device
 * \param[out] format The image format applied on the video device
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::getFormat(V4L2DeviceFormat *format)
{
	switch (bufferType_) {
	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
		return getFormatSingleplane(format);
	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
		return getFormatMultiplane(format);
	case V4L2_BUF_TYPE_META_CAPTURE:
	case V4L2_BUF_TYPE_META_OUTPUT:
		return getFormatMeta(format);
	default:
		return -EINVAL;
	}
}

/**
 * \brief Try an image format on the V4L2 video device
 * \param[inout] format The image format to test applicability to the video device
 *
 * Try the supplied \a format on the video device without applying it, returning
 * the format that would be applied. This is equivalent to setFormat(), except
 * that the device configuration is not changed.
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::tryFormat(V4L2DeviceFormat *format)
{
	switch (bufferType_) {
	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
		return trySetFormatSingleplane(format, false);
	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
		return trySetFormatMultiplane(format, false);
	case V4L2_BUF_TYPE_META_CAPTURE:
	case V4L2_BUF_TYPE_META_OUTPUT:
		return trySetFormatMeta(format, false);
	default:
		return -EINVAL;
	}
}

/**
 * \brief Configure an image format on the V4L2 video device
 * \param[inout] format The image format to apply to the video device
 *
 * Apply the supplied \a format to the video 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)
{
	int ret;

	switch (bufferType_) {
	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
		ret = trySetFormatSingleplane(format, true);
		break;
	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
		ret = trySetFormatMultiplane(format, true);
		break;
	case V4L2_BUF_TYPE_META_CAPTURE:
	case V4L2_BUF_TYPE_META_OUTPUT:
		ret = trySetFormatMeta(format, true);
		break;
	default:
		ret = -EINVAL;
		break;
	}

	/* Cache the set format on success. */
	if (ret)
		return ret;

	format_ = *format;
	formatInfo_ = &PixelFormatInfo::info(format_.fourcc);

	return 0;
}

int V4L2VideoDevice::getFormatMeta(V4L2DeviceFormat *format)
{
	struct v4l2_format v4l2Format = {};
	struct v4l2_meta_format *pix = &v4l2Format.fmt.meta;
	int ret;

	v4l2Format.type = bufferType_;
	ret = ioctl(VIDIOC_G_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error) << "Unable to get format: " << strerror(-ret);
		return ret;
	}

	format->size.width = 0;
	format->size.height = 0;
	format->fourcc = V4L2PixelFormat(pix->dataformat);
	format->planesCount = 1;
	format->planes[0].bpl = pix->buffersize;
	format->planes[0].size = pix->buffersize;

	return 0;
}

int V4L2VideoDevice::trySetFormatMeta(V4L2DeviceFormat *format, bool set)
{
	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(set ? VIDIOC_S_FMT : VIDIOC_TRY_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error)
			<< "Unable to " << (set ? "set" : "try")
			<< " format: " << strerror(-ret);
		return ret;
	}

	/*
	 * Return to caller the format actually applied on the video device,
	 * which might differ from the requested one.
	 */
	format->size.width = 0;
	format->size.height = 0;
	format->fourcc = V4L2PixelFormat(pix->dataformat);
	format->planesCount = 1;
	format->planes[0].bpl = pix->buffersize;
	format->planes[0].size = pix->buffersize;

	return 0;
}

template<typename T>
std::optional<ColorSpace> V4L2VideoDevice::toColorSpace(const T &v4l2Format)
{
	V4L2PixelFormat fourcc{ v4l2Format.pixelformat };
	return V4L2Device::toColorSpace(v4l2Format, PixelFormatInfo::info(fourcc).colourEncoding);
}

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(VIDIOC_G_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error) << "Unable to get format: " << strerror(-ret);
		return ret;
	}

	format->size.width = pix->width;
	format->size.height = pix->height;
	format->fourcc = V4L2PixelFormat(pix->pixelformat);
	format->planesCount = pix->num_planes;
	format->colorSpace = toColorSpace(*pix);

	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::trySetFormatMultiplane(V4L2DeviceFormat *format, bool set)
{
	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;
	if (format->colorSpace) {
		fromColorSpace(format->colorSpace, *pix);

		if (caps_.isVideoCapture())
			pix->flags |= V4L2_PIX_FMT_FLAG_SET_CSC;
	}

	ASSERT(pix->num_planes <= std::size(pix->plane_fmt));

	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(set ? VIDIOC_S_FMT : VIDIOC_TRY_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error)
			<< "Unable to " << (set ? "set" : "try")
			<< " format: " << strerror(-ret);
		return ret;
	}

	/*
	 * Return to caller the format actually applied on the video device,
	 * which might differ from the requested one.
	 */
	format->size.width = pix->width;
	format->size.height = pix->height;
	format->fourcc = V4L2PixelFormat(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;
	}
	format->colorSpace = toColorSpace(*pix);

	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(VIDIOC_G_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error) << "Unable to get format: " << strerror(-ret);
		return ret;
	}

	format->size.width = pix->width;
	format->size.height = pix->height;
	format->fourcc = V4L2PixelFormat(pix->pixelformat);
	format->planesCount = 1;
	format->planes[0].bpl = pix->bytesperline;
	format->planes[0].size = pix->sizeimage;
	format->colorSpace = toColorSpace(*pix);

	return 0;
}

int V4L2VideoDevice::trySetFormatSingleplane(V4L2DeviceFormat *format, bool set)
{
	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;
	if (format->colorSpace) {
		fromColorSpace(format->colorSpace, *pix);

		if (caps_.isVideoCapture())
			pix->flags |= V4L2_PIX_FMT_FLAG_SET_CSC;
	}

	ret = ioctl(set ? VIDIOC_S_FMT : VIDIOC_TRY_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error)
			<< "Unable to " << (set ? "set" : "try")
			<< " 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 = V4L2PixelFormat(pix->pixelformat);
	format->planesCount = 1;
	format->planes[0].bpl = pix->bytesperline;
	format->planes[0].size = pix->sizeimage;
	format->colorSpace = toColorSpace(*pix);

	return 0;
}

/**
 * \brief Enumerate all pixel formats and frame sizes
 * \param[in] code Restrict formats to this media bus code.
 *
 * Enumerate all pixel formats and frame sizes supported by the video device.
 * If the \a code argument is not zero, only formats compatible with that media
 * bus code will be enumerated.
 *
 * \return A list of the supported video device formats
 */
V4L2VideoDevice::Formats V4L2VideoDevice::formats(uint32_t code)
{
	Formats formats;

	for (V4L2PixelFormat pixelFormat : enumPixelformats(code)) {
		std::vector<SizeRange> sizes = enumSizes(pixelFormat);
		if (sizes.empty())
			return {};

		if (formats.find(pixelFormat) != formats.end()) {
			LOG(V4L2, Error)
				<< "Could not add sizes for pixel format "
				<< pixelFormat;
			return {};
		}

		formats.emplace(pixelFormat, sizes);
	}

	return formats;
}

std::vector<V4L2PixelFormat> V4L2VideoDevice::enumPixelformats(uint32_t code)
{
	std::vector<V4L2PixelFormat> formats;
	int ret;

	if (code && !caps_.hasMediaController()) {
		LOG(V4L2, Error)
			<< "Media bus code filtering not supported by the device";
		return {};
	}

	for (unsigned int index = 0; ; index++) {
		struct v4l2_fmtdesc pixelformatEnum = {};
		pixelformatEnum.index = index;
		pixelformatEnum.type = bufferType_;
		pixelformatEnum.mbus_code = code;

		ret = ioctl(VIDIOC_ENUM_FMT, &pixelformatEnum);
		if (ret)
			break;

		formats.push_back(V4L2PixelFormat(pixelformatEnum.pixelformat));
	}

	if (ret && ret != -EINVAL) {
		LOG(V4L2, Error)
			<< "Unable to enumerate pixel formats: "
			<< strerror(-ret);
		return {};
	}

	return formats;
}

std::vector<SizeRange> V4L2VideoDevice::enumSizes(V4L2PixelFormat 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(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(Size{ frameSize.discrete.width,
						 frameSize.discrete.height });
			break;
		case V4L2_FRMSIZE_TYPE_CONTINUOUS:
			sizes.emplace_back(Size{ frameSize.stepwise.min_width,
						 frameSize.stepwise.min_height },
					   Size{ frameSize.stepwise.max_width,
						 frameSize.stepwise.max_height });
			break;
		case V4L2_FRMSIZE_TYPE_STEPWISE:
			sizes.emplace_back(Size{ frameSize.stepwise.min_width,
						 frameSize.stepwise.min_height },
					   Size{ 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 && ret != -EINVAL) {
		LOG(V4L2, Error)
			<< "Unable to enumerate frame sizes: "
			<< strerror(-ret);
		return {};
	}

	return sizes;
}

/**
 * \brief Set a selection rectangle \a rect for \a target
 * \param[in] target The selection target defined by the V4L2_SEL_TGT_* flags
 * \param[inout] rect The selection rectangle to be applied
 *
 * \todo Define a V4L2SelectionTarget enum for the selection target
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::setSelection(unsigned int target, Rectangle *rect)
{
	struct v4l2_selection sel = {};

	sel.type = bufferType_;
	sel.target = target;
	sel.flags = 0;

	sel.r.left = rect->x;
	sel.r.top = rect->y;
	sel.r.width = rect->width;
	sel.r.height = rect->height;

	int ret = ioctl(VIDIOC_S_SELECTION, &sel);
	if (ret < 0) {
		LOG(V4L2, Error) << "Unable to set rectangle " << target
				 << ": " << strerror(-ret);
		return ret;
	}

	rect->x = sel.r.left;
	rect->y = sel.r.top;
	rect->width = sel.r.width;
	rect->height = sel.r.height;

	return 0;
}

int V4L2VideoDevice::requestBuffers(unsigned int count,
				    enum v4l2_memory memoryType)
{
	struct v4l2_requestbuffers rb = {};
	int ret;

	rb.count = count;
	rb.type = bufferType_;
	rb.memory = memoryType;

	ret = ioctl(VIDIOC_REQBUFS, &rb);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Unable to request " << count << " buffers: "
			<< strerror(-ret);
		return ret;
	}

	if (rb.count < count) {
		LOG(V4L2, Error)
			<< "Not enough buffers provided by V4L2VideoDevice";
		requestBuffers(0, memoryType);
		return -ENOMEM;
	}

	LOG(V4L2, Debug) << rb.count << " buffers requested.";

	return 0;
}

/**
 * \brief Allocate and export buffers from the video device
 * \param[in] count Number of buffers to allocate
 * \param[out] buffers Vector to store allocated buffers
 *
 * This function wraps buffer allocation with the V4L2 MMAP memory type. It
 * requests \a count buffers from the driver, allocating the corresponding
 * memory, and exports them as a set of FrameBuffer objects in \a buffers. Upon
 * successful return the driver's internal buffer management is initialized in
 * MMAP mode, and the video device is ready to accept queueBuffer() calls.
 *
 * The number of planes and their offsets and sizes are determined by the
 * currently active format on the device as set by setFormat(). They do not map
 * to the V4L2 buffer planes, but to colour planes of the pixel format. For
 * instance, if the active format is formats::NV12, the allocated FrameBuffer
 * instances will have two planes, for the luma and chroma components,
 * regardless of whether the device uses V4L2_PIX_FMT_NV12 or
 * V4L2_PIX_FMT_NV12M.
 *
 * Buffers allocated with this function shall later be free with
 * releaseBuffers(). If buffers have already been allocated with
 * allocateBuffers() or imported with importBuffers(), this function returns
 * -EBUSY.
 *
 * \return The number of allocated buffers on success or a negative error code
 * otherwise
 * \retval -EBUSY buffers have already been allocated or imported
 */
int V4L2VideoDevice::allocateBuffers(unsigned int count,
				     std::vector<std::unique_ptr<FrameBuffer>> *buffers)
{
	int ret = createBuffers(count, buffers);
	if (ret < 0)
		return ret;

	cache_ = new V4L2BufferCache(*buffers);
	memoryType_ = V4L2_MEMORY_MMAP;

	return ret;
}

/**
 * \brief Export buffers from the video device
 * \param[in] count Number of buffers to allocate
 * \param[out] buffers Vector to store allocated buffers
 *
 * This function allocates \a count buffer from the video device and exports
 * them as dmabuf objects, stored in \a buffers. Unlike allocateBuffers(), this
 * function leaves the driver's internal buffer management uninitialized. The
 * video device shall be initialized with importBuffers() or allocateBuffers()
 * before it can accept queueBuffer() calls. The exported buffers are directly
 * usable with any V4L2 video device in DMABUF mode, or with other dmabuf
 * importers.
 *
 * The number of planes and their offsets and sizes are determined by the
 * currently active format on the device as set by setFormat(). They do not map
 * to the V4L2 buffer planes, but to colour planes of the pixel format. For
 * instance, if the active format is formats::NV12, the allocated FrameBuffer
 * instances will have two planes, for the luma and chroma components,
 * regardless of whether the device uses V4L2_PIX_FMT_NV12 or
 * V4L2_PIX_FMT_NV12M.
 *
 * Multiple independent sets of buffers can be allocated with multiple calls to
 * this function. Device-specific limitations may apply regarding the minimum
 * and maximum number of buffers per set, or to total amount of allocated
 * memory. The exported dmabuf lifetime is tied to the returned \a buffers. To
 * free a buffer, the caller shall delete the corresponding FrameBuffer
 * instance. No bookkeeping and automatic free is performed by the
 * V4L2VideoDevice class.
 *
 * If buffers have already been allocated with allocateBuffers() or imported
 * with importBuffers(), this function returns -EBUSY.
 *
 * \return The number of allocated buffers on success or a negative error code
 * otherwise
 * \retval -EBUSY buffers have already been allocated or imported
 */
int V4L2VideoDevice::exportBuffers(unsigned int count,
				   std::vector<std::unique_ptr<FrameBuffer>> *buffers)
{
	int ret = createBuffers(count, buffers);
	if (ret < 0)
		return ret;

	requestBuffers(0, V4L2_MEMORY_MMAP);

	return ret;
}

int V4L2VideoDevice::createBuffers(unsigned int count,
				   std::vector<std::unique_ptr<FrameBuffer>> *buffers)
{
	if (cache_) {
		LOG(V4L2, Error) << "Buffers already allocated";
		return -EINVAL;
	}

	int ret = requestBuffers(count, V4L2_MEMORY_MMAP);
	if (ret < 0)
		return ret;

	for (unsigned i = 0; i < count; ++i) {
		std::unique_ptr<FrameBuffer> buffer = createBuffer(i);
		if (!buffer) {
			LOG(V4L2, Error) << "Unable to create buffer";

			requestBuffers(0, V4L2_MEMORY_MMAP);
			buffers->clear();

			return -EINVAL;
		}

		buffers->push_back(std::move(buffer));
	}

	return count;
}

std::unique_ptr<FrameBuffer> V4L2VideoDevice::createBuffer(unsigned int index)
{
	struct v4l2_plane v4l2Planes[VIDEO_MAX_PLANES] = {};
	struct v4l2_buffer buf = {};

	buf.index = index;
	buf.type = bufferType_;
	buf.length = std::size(v4l2Planes);
	buf.m.planes = v4l2Planes;

	int ret = ioctl(VIDIOC_QUERYBUF, &buf);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Unable to query buffer " << index << ": "
			<< strerror(-ret);
		return nullptr;
	}

	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++) {
		UniqueFD fd = exportDmabufFd(buf.index, nplane);
		if (!fd.isValid())
			return nullptr;

		FrameBuffer::Plane plane;
		plane.fd = SharedFD(std::move(fd));
		/*
		 * V4L2 API doesn't provide dmabuf offset information of plane.
		 * Set 0 as a placeholder offset.
		 * \todo Set the right offset once V4L2 API provides a way.
		 */
		plane.offset = 0;
		plane.length = multiPlanar ? buf.m.planes[nplane].length : buf.length;

		planes.push_back(std::move(plane));
	}

	/*
	 * If we have a multi-planar format with a V4L2 single-planar buffer,
	 * split the single V4L2 plane into multiple FrameBuffer planes by
	 * computing the offsets manually.
	 *
	 * The format info is not guaranteed to be valid, as there are no
	 * PixelFormatInfo for metadata formats, so check it first.
	 */
	if (formatInfo_->isValid() && formatInfo_->numPlanes() != numPlanes) {
		/*
		 * There's no valid situation where the number of colour planes
		 * differs from the number of V4L2 planes and the V4L2 buffer
		 * has more than one plane.
		 */
		ASSERT(numPlanes == 1u);

		planes.resize(formatInfo_->numPlanes());
		const SharedFD &fd = planes[0].fd;
		size_t offset = 0;

		for (auto [i, plane] : utils::enumerate(planes)) {
			/*
			 * The stride is reported by V4L2 for the first plane
			 * only. Compute the stride of the other planes by
			 * taking the horizontal subsampling factor into
			 * account, which is equal to the bytesPerGroup ratio of
			 * the planes.
			 */
			unsigned int stride = format_.planes[0].bpl
					    * formatInfo_->planes[i].bytesPerGroup
					    / formatInfo_->planes[0].bytesPerGroup;

			plane.fd = fd;
			plane.offset = offset;
			plane.length = formatInfo_->planeSize(format_.size.height,
							      i, stride);
			offset += plane.length;
		}
	}

	return std::make_unique<FrameBuffer>(planes);
}

UniqueFD V4L2VideoDevice::exportDmabufFd(unsigned int index,
					 unsigned int plane)
{
	struct v4l2_exportbuffer expbuf = {};
	int ret;

	expbuf.type = bufferType_;
	expbuf.index = index;
	expbuf.plane = plane;
	expbuf.flags = O_CLOEXEC | O_RDWR;

	ret = ioctl(VIDIOC_EXPBUF, &expbuf);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Failed to export buffer: " << strerror(-ret);
		return {};
	}

	return UniqueFD(expbuf.fd);
}

/**
 * \brief Prepare the device to import \a count buffers
 * \param[in] count Number of buffers to prepare to import
 *
 * This function initializes the driver's buffer management to import buffers
 * in DMABUF mode. It requests buffers from the driver, but doesn't allocate
 * memory.
 *
 * Upon successful return, the video device is ready to accept queueBuffer()
 * calls. The buffers to be imported are provided to queueBuffer(), and may be
 * supplied externally, or come from a previous exportBuffers() call.
 *
 * Device initialization performed by this function shall later be cleaned up
 * with releaseBuffers(). If buffers have already been allocated with
 * allocateBuffers() or imported with importBuffers(), this function returns
 * -EBUSY.
 *
 * \return 0 on success or a negative error code otherwise
 * \retval -EBUSY buffers have already been allocated or imported
 */