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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2019, Google Inc.
*
* v4l2_device.cpp - Common base for V4L2 video devices and subdevices
*/
#include "v4l2_device.h"
#include <fcntl.h>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include "log.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 methods and fields common to
* both the V4L2VideoDevice and V4L2Subdevice classes, and provides a base
* class whith methods 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), fd_(-1)
{
}
/**
* \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;
}
int ret = ::open(deviceNode_.c_str(), flags);
if (ret < 0) {
ret = -errno;
LOG(V4L2, Error) << "Failed to open V4L2 device: "
<< strerror(-ret);
return ret;
}
fd_ = ret;
return 0;
}
/**
* \brief Close the device node
*
* Reset the file descriptor to -1
*/
void V4L2Device::close()
{
if (!isOpen())
return;
if (::close(fd_) < 0)
LOG(V4L2, Error) << "Failed to close V4L2 device: "
<< strerror(errno);
fd_ = -1;
}
/**
* \fn V4L2Device::isOpen()
* \brief Check if the V4L2 device node is open
* \return True if the V4L2 device node is open, false otherwise
*/
/**
* \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_, 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
*/
} /* namespace libcamera */
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