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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2021, Google Inc.
*
* mapped_buffer.cpp - Mapped Buffer handling
*/
#include "libcamera-helpers/mapped_buffer.h"
#include <errno.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
#include <libcamera/base/log.h>
/**
* \file libcamera-helpers/mapped_buffer.h
* \brief Mapped Buffer handling
*/
namespace libcamera {
LOG_DEFINE_CATEGORY(MappedBuffer)
/**
* \class MappedBuffer
* \brief Provide an interface to support managing memory mapped buffers
*
* The MappedBuffer interface provides access to a set of MappedPlanes which
* are available for access by the CPU.
*
* This class is not meant to be constructed directly, but instead derived
* classes should be used to implement the correct mapping of a source buffer.
*
* This allows treating CPU accessible memory through a generic interface
* regardless of whether it originates from a libcamera FrameBuffer or other
* source.
*/
/**
* \typedef MappedBuffer::Plane
* \brief A mapped region of memory accessible to the CPU
*
* The MappedBuffer::Plane uses the Span interface to describe the mapped memory
* region.
*/
/**
* \brief Construct an empty MappedBuffer
*/
MappedBuffer::MappedBuffer()
: error_(0)
{
}
/**
* \brief Move constructor, construct the MappedBuffer with the contents of \a
* other using move semantics
* \param[in] other The other MappedBuffer
*
* Moving a MappedBuffer moves the mappings contained in the \a other to the new
* MappedBuffer and invalidates the \a other.
*
* No mappings are unmapped or destroyed in this process.
*/
MappedBuffer::MappedBuffer(MappedBuffer &&other)
{
*this = std::move(other);
}
/**
* \brief Move assignment operator, replace the mappings with those of \a other
* \param[in] other The other MappedBuffer
*
* Moving a MappedBuffer moves the mappings contained in the \a other to the new
* MappedBuffer and invalidates the \a other.
*
* No mappings are unmapped or destroyed in this process.
*/
MappedBuffer &MappedBuffer::operator=(MappedBuffer &&other)
{
error_ = other.error_;
maps_ = std::move(other.maps_);
other.error_ = -ENOENT;
return *this;
}
MappedBuffer::~MappedBuffer()
{
for (Plane &map : maps_)
munmap(map.data(), map.size());
}
/**
* \fn MappedBuffer::isValid()
* \brief Check if the MappedBuffer instance is valid
* \return True if the MappedBuffer has valid mappings, false otherwise
*/
/**
* \fn MappedBuffer::error()
* \brief Retrieve the map error status
*
* This function retrieves the error status from the MappedBuffer.
* The error status is a negative number as defined by errno.h. If
* no error occurred, this function returns 0.
*
* \return The map error code
*/
/**
* \fn MappedBuffer::maps()
* \brief Retrieve the mapped planes
*
* This function retrieves the successfully mapped planes stored as a vector
* of Span<uint8_t> to provide access to the mapped memory.
*
* \return A vector of the mapped planes
*/
/**
* \var MappedBuffer::error_
* \brief Stores the error value if present
*
* MappedBuffer derived classes shall set this to a negative value as defined
* by errno.h if an error occured during the mapping process.
*/
/**
* \var MappedBuffer::maps_
* \brief Stores the internal mapped planes
*
* MappedBuffer derived classes shall store the mappings they create in this
* vector which is parsed during destruct to unmap any memory mappings which
* completed successfully.
*/
/**
* \class MappedFrameBuffer
* \brief Map a FrameBuffer using the MappedBuffer interface
*/
/**
* \brief Map all planes of a FrameBuffer
* \param[in] buffer FrameBuffer to be mapped
* \param[in] flags Protection flags to apply to map
*
* Construct an object to map a frame buffer for CPU access.
* The flags are passed directly to mmap and should be either PROT_READ,
* PROT_WRITE, or a bitwise-or combination of both.
*/
MappedFrameBuffer::MappedFrameBuffer(const FrameBuffer *buffer, int flags)
{
maps_.reserve(buffer->planes().size());
for (const FrameBuffer::Plane &plane : buffer->planes()) {
void *address = mmap(nullptr, plane.length, flags,
MAP_SHARED, plane.fd.fd(), 0);
if (address == MAP_FAILED) {
error_ = -errno;
LOG(MappedBuffer, Error) << "Failed to mmap plane";
break;
}
maps_.emplace_back(static_cast<uint8_t *>(address), plane.length);
}
}
} /* namespace libcamera */
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