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path: root/src/cam

/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * Common base for V4L2 video devices and subdevices
 */

#include "libcamera/internal/v4l2_device.h"

#include <fcntl.h>
#include <iomanip>
#include <limits.h>
#include <map>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <vector>

#include <linux/v4l2-mediabus.h>

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

#include "libcamera/internal/formats.h"
#include "libcamera/internal/sysfs.h"

/**
 * \file v4l2_device.h
 * \brief Common base for V4L2 devices and subdevices
 */

namespace libcamera {

LOG_DEFINE_CATEGORY(V4L2)

/**
 * \class V4L2Device
 * \brief Base class for V4L2VideoDevice and V4L2Subdevice
 *
 * The V4L2Device class groups together the functions and fields common to
 * both the V4L2VideoDevice and V4L2Subdevice classes, and provides a base
 * class with functions to open and close the device node associated with the
 * device and to perform IOCTL system calls on it.
 *
 * The V4L2Device class cannot be instantiated directly, as its constructor
 * is protected. Users should instead create instances of one the derived
 * classes to model either a V4L2 video device or a V4L2 subdevice.
 */

/**
 * \brief Construct a V4L2Device
 * \param[in] deviceNode The device node filesystem path
 *
 * Initialize the file descriptor to -1 and store the \a deviceNode to be used
 * at open() time, and the \a logTag to prefix log messages with.
 */
V4L2Device::V4L2Device(const std::string &deviceNode)
	: deviceNode_(deviceNode), fdEventNotifier_(nullptr),
	  frameStartEnabled_(false)
{
}

/**
 * \brief Destroy a V4L2Device
 */
V4L2Device::~V4L2Device()
{
}

/**
 * \brief Open a V4L2 device node
 * \param[in] flags Access mode flags
 *
 * Open the device node path with the provided access mode \a flags and
 * initialize the file descriptor, which was initially set to -1.
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2Device::open(unsigned int flags)
{
	if (isOpen()) {
		LOG(V4L2, Error) << "Device already open";
		return -EBUSY;
	}

	UniqueFD fd(syscall(SYS_openat, AT_FDCWD, deviceNode_.c_str(),
			    flags | O_CLOEXEC));
	if (!fd.isValid()) {
		int ret = -errno;
		LOG(V4L2, Error) << "Failed to open V4L2 device '"
				 << deviceNode_ << "': "
				 << strerror(-ret);
		return ret;
	}

	setFd(std::move(fd));

	return 0;
}

/**
 * \brief Set the file descriptor of a V4L2 device
 * \param[in] fd The file descriptor handle
 *
 * This function allows a device to provide an already opened file descriptor
 * referring to the V4L2 device node, instead of opening it with open(). This
 * can be used for V4L2 M2M devices where a single video device node is used for
 * both the output and capture devices, or when receiving an open file
 * descriptor in a context that doesn't have permission to open the device node
 * itself.
 *
 * This function and the open() function are mutually exclusive, only one of the
 * two shall be used for a V4L2Device instance.
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2Device::setFd(UniqueFD fd)
{
	if (isOpen())
		return -EBUSY;

	fd_ = std::move(fd);

	fdEventNotifier_ = new EventNotifier(fd_.get(), EventNotifier::Exception);
	fdEventNotifier_->activated.connect(this, &V4L2Device::eventAvailable);
	fdEventNotifier_->setEnabled(false);

	listControls();

	return 0;
}

/**
 * \brief Close the device node
 *
 * Reset the file descriptor to -1
 */
void V4L2Device::close()
{
	if (!isOpen())
		return;

	delete fdEventNotifier_;

	fd_.reset();
}

/**
 * \fn V4L2Device::isOpen()
 * \brief Check if the V4L2 device node is open
 * \return True if the V4L2 device node is open, false otherwise
 */

/**
 * \fn V4L2Device::controls()
 * \brief Retrieve the supported V4L2 controls and their information
 * \return A map of the V4L2 controls supported by the device
 */

/**
 * \brief Read controls from the device
 * \param[in] ids The list of controls to read, specified by their ID
 *
 * This function reads the value of all controls contained in \a ids, and
 * returns their values as a ControlList.
 *
 * If any control in \a ids is not supported by the device, is disabled (i.e.
 * has the V4L2_CTRL_FLAG_DISABLED flag set), or if any other error occurs
 * during validation of the requested controls, no control is read and this
 * function returns an empty control list.
 *
 * \return The control values in a ControlList on success, or an empty list on
 * error
 */
ControlList V4L2Device::getControls(const std::vector<uint32_t> &ids)
{
	if (ids.empty())
		return {};

	ControlList ctrls{ controls_ };

	for (uint32_t id : ids) {
		const auto iter = controls_.find(id);
		if (iter == controls_.end()) {
			LOG(V4L2, Error)
				<< "Control " << utils::hex(id) << " not found";
			return {};
		}

		ctrls.set(id, {});
	}

	std::vector<v4l2_ext_control> v4l2Ctrls(ids.size());
	memset(v4l2Ctrls.data(), 0, sizeof(v4l2_ext_control) * ctrls.size());

	unsigned int i = 0;
	for (auto &ctrl : ctrls) {
		unsigned int id = ctrl.first;
		const struct v4l2_query_ext_ctrl &info = controlInfo_[id];

		v4l2_ext_control &v4l2Ctrl = v4l2Ctrls[i++];
		v4l2Ctrl.id = id;

		if (info.flags & V4L2_CTRL_FLAG_HAS_PAYLOAD) {
			ControlType type;

			switch (info.type) {
			case V4L2_CTRL_TYPE_U8:
				type = ControlTypeByte;
				break;

			default:
				LOG(V4L2, Error)
					<< "Unsupported payload control type "
					<< info.type;
				return {};
			}

			ControlValue &value = ctrl.second;
			value.reserve(type, true, info.elems);
			Span<uint8_t> data = value.data();

			v4l2Ctrl.p_u8 = data.data();
			v4l2Ctrl.size = data.size();
		}
	}

	struct v4l2_ext_controls v4l2ExtCtrls = {};
	v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
	v4l2ExtCtrls.controls = v4l2Ctrls.data();
	v4l2ExtCtrls.count = v4l2Ctrls.size();

	int ret = ioctl(VIDIOC_G_EXT_CTRLS, &v4l2ExtCtrls);
	if (ret) {
		unsigned int errorIdx = v4l2ExtCtrls.error_idx;

		/* Generic validation error. */
		if (errorIdx == 0 || errorIdx >= v4l2Ctrls.size()) {
			LOG(V4L2, Error) << "Unable to read controls: "
					 << strerror(-ret);
			return {};
		}

		/* A specific control failed. */
		const unsigned int id = v4l2Ctrls[errorIdx].id;
		LOG(V4L2, Error) << "Unable to read control " << utils::hex(id)
				 << ": " << strerror(-ret);

		v4l2Ctrls.resize(errorIdx);
	}

	updateControls(&ctrls, v4l2Ctrls);

	return ctrls;
}

/**
 * \brief Write controls to the device
 * \param[in] ctrls The list of controls to write
 *
 * This function writes the value of all controls contained in \a ctrls, and
 * stores the values actually applied to the device in the corresponding
 * \a ctrls entry.
 *
 * If any control in \a ctrls is not supported by the device, is disabled (i.e.
 * has the V4L2_CTRL_FLAG_DISABLED flag set), is read-only, if any other error
 * occurs during validation of the requested controls, no control is written and
 * this function returns -EINVAL.
 *
 * If an error occurs while writing the controls, the index of the first
 * control that couldn't be written is returned. All controls below that index
 * are written and their values are updated in \a ctrls, while all other
 * controls are not written and their values are not changed.
 *
 * \return 0 on success or an error code otherwise
 * \retval -EINVAL One of the control is not supported or not accessible
 * \retval i The index of the control that failed
 */
int V4L2Device::setControls(ControlList *ctrls)
{
	if (ctrls->empty())
		return 0;

	std::vector<v4l2_ext_control> v4l2Ctrls(ctrls->size());
	memset(v4l2Ctrls.data(), 0, sizeof(v4l2_ext_control) * ctrls->size());

	for (auto [ctrl, i] = std::pair(ctrls->begin(), 0u); i < ctrls->size(); ctrl++, i++) {
		const unsigned int id = ctrl->first;
		const auto iter = controls_.find(id);
		if (iter == controls_.end()) {
			LOG(V4L2, Error)
				<< "Control " << utils::hex(id) << " not found";
			return -EINVAL;
		}
		v4l2_ext_control &v4l2Ctrl = v4l2Ctrls[i];
		v4l2Ctrl.id = id;

		/* Set the v4l2_ext_control value for the write operation. */
		ControlValue &value = ctrl->second;
		switch (iter->first->type()) {
		case ControlTypeInteger32: {
			if (value.isArray()) {
				Span<uint8_t> data = value.data();
				v4l2Ctrl.p_u32 = reinterpret_cast<uint32_t *>(data.data());
				v4l2Ctrl.size = data.size();
			} else {
				v4l2Ctrl.value = value.get<int32_t>();
			}

			break;
		}

		case ControlTypeInteger64:
			v4l2Ctrl.value64 = value.get<int64_t>();
			break;

		case ControlTypeByte: {
			if (!value.isArray()) {
				LOG(V4L2, Error)
					<< "Control " << utils::hex(id)
					<< " requires an array value";
				return -EINVAL;
			}

			Span<uint8_t> data = value.data();
			v4l2Ctrl.p_u8 = data.data();
			v4l2Ctrl.size = data.size();

			break;
		}

		default:
			/* \todo To be changed to support strings. */
			v4l2Ctrl.value = value.get<int32_t>();
			break;
		}
	}

	struct v4l2_ext_controls v4l2ExtCtrls = {};
	v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
	v4l2ExtCtrls.controls = v4l2Ctrls.data();
	v4l2ExtCtrls.count = v4l2Ctrls.size();

	int ret = ioctl(VIDIOC_S_EXT_CTRLS, &v4l2ExtCtrls);
	if (ret) {
		unsigned int errorIdx = v4l2ExtCtrls.error_idx;

		/* Generic validation error. */
		if (errorIdx == 0 || errorIdx >= v4l2Ctrls.size()) {
			LOG(V4L2, Error) << "Unable to set controls: "
					 << strerror(-ret);
			return -EINVAL;
		}

		/* A specific control failed. */
		const unsigned int id = v4l2Ctrls[errorIdx].id;
		LOG(V4L2, Error) << "Unable to set control " << utils::hex(id)
				 << ": " << strerror(-ret);

		v4l2Ctrls.resize(errorIdx);
		ret = errorIdx;
	}

	updateControls(ctrls, v4l2Ctrls);

	return ret;
}

/**
 * \brief Retrieve the v4l2_query_ext_ctrl information for the given control
 * \param[in] id The V4L2 control id
 * \return A pointer to the v4l2_query_ext_ctrl structure for the given
 * control, or a null pointer if not found
 */
const struct v4l2_query_ext_ctrl *V4L2Device::controlInfo(uint32_t id) const
{
	const auto it = controlInfo_.find(id);
	if (it == controlInfo_.end())
		return nullptr;

	return &it->second;
}

/**
 * \brief Retrieve the device path in sysfs
 *
 * This function returns the sysfs path to the physical device backing the V4L2
 * device. The path is guaranteed to be an absolute path, without any symbolic
 * link.
 *
 * It includes the sysfs mount point prefix
 *
 * \return The device path in sysfs
 */
std::string V4L2Device::devicePath() const
{
	std::string devicePath = sysfs::charDevPath(deviceNode_) + "/device";

	char *realPath = realpath(devicePath.c_str(), nullptr);
	if (!realPath) {
		LOG(V4L2, Fatal)
			<< "Can not resolve device path for " << devicePath;
		return {};
	}

	std::string path{ realPath };
	free(realPath);

	return path;
}

/**
 * \brief Enable or disable frame start event notification
 * \param[in] enable True to enable frame start events, false to disable them
 *
 * This function enables or disables generation of frame start events. Once
 * enabled, the events are signalled through the frameStart signal.
 *
 * \return 0 on success, a negative error code otherwise
 */
int V4L2Device::setFrameStartEnabled(bool enable)
{
	if (frameStartEnabled_ == enable)
		return 0;

	struct v4l2_event_subscription event{};
	event.type = V4L2_EVENT_FRAME_SYNC;

	unsigned long request = enable ? VIDIOC_SUBSCRIBE_EVENT
			      : VIDIOC_UNSUBSCRIBE_EVENT;
	int ret = ioctl(request, &event);
	if (enable && ret)
		return ret;

	fdEventNotifier_->setEnabled(enable);
	frameStartEnabled_ = enable;

	return ret;
}

/**
 * \var V4L2Device::frameStart
 * \brief A Signal emitted when capture of a frame has started
 */

/**
 * \brief Perform an IOCTL system call on the device node
 * \param[in] request The IOCTL request code
 * \param[in] argp A pointer to the IOCTL argument
 * \return 0 on success or a negative error code otherwise
 */
int V4L2Device::ioctl(unsigned long request, void *argp)
{
	/*
	 * Printing out an error message is usually better performed
	 * in the caller, which can provide more context.
	 */
	if (::ioctl(fd_.get(), request, argp) < 0)
		return -errno;

	return 0;
}

/**
 * \fn V4L2Device::deviceNode()
 * \brief Retrieve the device node path
 * \return The device node path
 */

/**
 * \fn V4L2Device::fd()
 * \brief Retrieve the V4L2 device file descriptor
 * \return The V4L2 device file descriptor, -1 if the device node is not open
 */

/**
 * \brief Retrieve the libcamera control type associated with the V4L2 control
 * \param[in] ctrlType The V4L2 control type
 * \return The ControlType associated to \a ctrlType
 */
ControlType V4L2Device::v4l2CtrlType(uint32_t ctrlType)
{
	switch (ctrlType) {
	case V4L2_CTRL_TYPE_U8:
		return ControlTypeByte;

	case V4L2_CTRL_TYPE_BOOLEAN:
		return ControlTypeBool;

	case V4L2_CTRL_TYPE_INTEGER:
		return ControlTypeInteger32;

	case V4L2_CTRL_TYPE_INTEGER64:
		return ControlTypeInteger64;

	case V4L2_CTRL_TYPE_MENU:
	case V4L2_CTRL_TYPE_BUTTON:
	case V4L2_CTRL_TYPE_BITMASK:
	case V4L2_CTRL_TYPE_INTEGER_MENU:
		/*
		 * More precise types may be needed, for now use a 32-bit
		 * integer type.
		 */
		return ControlTypeInteger32;

	default:
		return ControlTypeNone;
	}
}

/**
 * \brief Create a ControlId for a V4L2 control
 * \param[in] ctrl The v4l2_query_ext_ctrl that represents a V4L2 control
 * \return A ControlId associated to \a ctrl
 */
std::unique_ptr<ControlId> V4L2Device::v4l2ControlId(const v4l2_query_ext_ctrl &ctrl)
{
	const size_t len = strnlen(ctrl.name, sizeof(ctrl.name));
	const std::string name(static_cast<const char *>(ctrl.name), len);
	const ControlType type = v4l2CtrlType(ctrl.type);

	return std::make_unique<ControlId>(ctrl.id, name, type);
}

/**
 * \brief Create a ControlInfo for a V4L2 control
 * \param[in] ctrl The v4l2_query_ext_ctrl that represents a V4L2 control
 * \return A ControlInfo that represents \a ctrl
 */
std::optional<ControlInfo> V4L2Device::v4l2ControlInfo(const v4l2_query_ext_ctrl &ctrl)
{
	switch (ctrl.type) {
	case V4L2_CTRL_TYPE_U8:
		return ControlInfo(static_cast<uint8_t>(ctrl.minimum),
				   static_cast<uint8_t>(ctrl.maximum),
				   static_cast<uint8_t>(ctrl.default_value));

	case V4L2_CTRL_TYPE_BOOLEAN:
		return ControlInfo(static_cast<bool>(ctrl.minimum),
				   static_cast<bool>(ctrl.maximum),
				   static_cast<bool>(ctrl.default_value));

	case V4L2_CTRL_TYPE_INTEGER64:
		return ControlInfo(static_cast<int64_t>(ctrl.minimum),
				   static_cast<int64_t>(ctrl.maximum),
				   static_cast<int64_t>(ctrl.default_value));

	case V4L2_CTRL_TYPE_INTEGER_MENU:
	case V4L2_CTRL_TYPE_MENU:
		return v4l2MenuControlInfo(ctrl);

	default:
		return ControlInfo(static_cast<int32_t>(ctrl.minimum),
				   static_cast<int32_t>(ctrl.maximum),
				   static_cast<int32_t>(ctrl.default_value));
	}
}

/**
 * \brief Create ControlInfo for a V4L2 menu control
 * \param[in] ctrl The v4l2_query_ext_ctrl that represents a V4L2 menu control
 *
 * The created ControlInfo contains indices acquired by VIDIOC_QUERYMENU.
 *
 * \return A ControlInfo that represents \a ctrl
 */
std::optional<ControlInfo> V4L2Device::v4l2MenuControlInfo(const struct v4l2_query_ext_ctrl &ctrl)