e74f3eebb4
Provide a helper V4L2 device object capable of interacting with the V4L2 Linux Kernel APIs. Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
186 lines
4.2 KiB
C++
186 lines
4.2 KiB
C++
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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/*
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* Copyright (C) 2019, Google Inc.
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*
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* v4l2_device.cpp - V4L2 Device
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*/
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#include <fcntl.h>
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#include <string.h>
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#include <sys/ioctl.h>
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#include <sys/mman.h>
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#include <unistd.h>
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#include "log.h"
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#include "v4l2_device.h"
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/**
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* \file v4l2_device.h
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* \brief V4L2 Device API
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*/
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namespace libcamera {
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/**
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* \struct V4L2Capability
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* \brief struct v4l2_capability object wrapper and helpers
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*
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* The V4L2Capability structure manages the information returned by the
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* VIDIOC_QUERYCAP ioctl.
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*/
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/**
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* \fn const char *V4L2Capability::driver()
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* \brief Retrieve the driver module name
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* \return The string containing the name of the driver module
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*/
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/**
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* \fn const char *V4L2Capability::card()
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* \brief Retrieve the device card name
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* \return The string containing the device name
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*/
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/**
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* \fn const char *V4L2Capability::bus_info()
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* \brief Retrieve the location of the device in the system
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* \return The string containing the device location
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*/
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/**
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* \fn bool V4L2Capability::isCapture()
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* \brief Identify if the device is capable of capturing video
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* \return True if the device can capture video frames
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*/
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/**
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* \fn bool V4L2Capability::isOutput()
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* \brief Identify if the device is capable of outputting video
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* \return True if the device can output video frames
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*/
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/**
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* \fn bool V4L2Capability::hasStreaming()
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* \brief Determine if the device can perform Streaming I/O
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* \return True if the device provides Streaming I/O IOCTLs
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*/
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/**
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* \class V4L2Device
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* \brief V4L2Device object and API
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*
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* The V4L2 Device API class models an instance of a V4L2 device node.
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* It is constructed with the path to a V4L2 video device node. The device node
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* is only opened upon a call to open() which must be checked for success.
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*
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* The device capabilities are validated when the device is opened and the
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* device is rejected if it is not a suitable V4L2 capture or output device, or
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* if the device does not support streaming I/O.
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*
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* No API call other than open(), isOpen() and close() shall be called on an
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* unopened device instance.
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*
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* Upon destruction any device left open will be closed, and any resources
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* released.
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*/
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/**
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* \brief Construct a V4L2Device
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* \param devnode The file-system path to the video device node
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*/
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V4L2Device::V4L2Device(const std::string &devnode)
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: devnode_(devnode), fd_(-1)
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{
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}
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V4L2Device::~V4L2Device()
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{
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close();
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}
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/**
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* \brief Open a V4L2 device and query its capabilities
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* \return 0 on success, or a negative error code otherwise
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*/
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int V4L2Device::open()
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{
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int ret;
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if (isOpen()) {
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LOG(Error) << "Device already open";
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return -EBUSY;
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}
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ret = ::open(devnode_.c_str(), O_RDWR);
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if (ret < 0) {
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ret = -errno;
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LOG(Error) << "Failed to open V4L2 device '" << devnode_
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<< "': " << strerror(-ret);
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return ret;
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}
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fd_ = ret;
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ret = ioctl(fd_, VIDIOC_QUERYCAP, &caps_);
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if (ret < 0) {
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ret = -errno;
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LOG(Error) << "Failed to query device capabilities: "
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<< strerror(-ret);
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return ret;
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}
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LOG(Debug) << "Opened '" << devnode_ << "' "
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<< caps_.bus_info() << ": " << caps_.driver()
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<< ": " << caps_.card();
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if (!caps_.isCapture() && !caps_.isOutput()) {
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LOG(Debug) << "Device is not a supported type";
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return -EINVAL;
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}
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if (!caps_.hasStreaming()) {
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LOG(Error) << "Device does not support streaming I/O";
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return -EINVAL;
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}
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return 0;
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}
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/**
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* \brief Check if device is successfully opened
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* \return True if the device is open, false otherwise
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*/
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bool V4L2Device::isOpen() const
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{
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return fd_ != -1;
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}
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/**
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* \brief Close the device, releasing any resources acquired by open()
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*/
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void V4L2Device::close()
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{
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if (fd_ < 0)
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return;
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::close(fd_);
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fd_ = -1;
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}
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/**
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* \fn const char *V4L2Device::driverName()
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* \brief Retrieve the name of the V4L2 device driver
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* \return The string containing the driver name
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*/
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/**
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* \fn const char *V4L2Device::deviceName()
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* \brief Retrieve the name of the V4L2 device
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* \return The string containing the device name
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*/
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/**
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* \fn const char *V4L2Device::busName()
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* \brief Retrieve the location of the device in the system
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* \return The string containing the device location
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*/
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} /* namespace libcamera */
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