/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * buffer.cpp - Buffer handling
 */

#include <libcamera/buffer.h>

#include <errno.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>

#include "log.h"

/**
 * \file buffer.h
 * \brief Buffer handling
 */

namespace libcamera {

LOG_DEFINE_CATEGORY(Buffer)

/**
 * \class Plane
 * \brief A memory region to store a single plane of a frame
 *
 * Planar pixel formats use multiple memory regions to store planes
 * corresponding to the different colour components of a frame. The Plane class
 * tracks the specific details of a memory region used to store a single plane
 * for a given frame and provides the means to access the memory, both for the
 * application and for DMA. A Buffer then contains one or multiple planes
 * depending on its pixel format.
 *
 * To support DMA access, planes are associated with dmabuf objects represented
 * by file handles. Each plane carries a dmabuf file handle and an offset within
 * the buffer. Those file handles may refer to the same dmabuf object, depending
 * on whether the devices accessing the memory regions composing the image
 * support non-contiguous DMA to planes ore require DMA-contiguous memory.
 *
 * To support CPU access, planes carry the CPU address of their backing memory.
 * Similarly to the dmabuf file handles, the CPU addresses for planes composing
 * an image may or may not be contiguous.
 */

Plane::Plane()
	: fd_(-1), length_(0), mem_(0)
{
}

Plane::~Plane()
{
	munmap();

	if (fd_ != -1)
		close(fd_);
}

/**
 * \fn Plane::dmabuf()
 * \brief Get the dmabuf file handle backing the buffer
 */

/**
 * \brief Set the dmabuf file handle backing the buffer
 * \param[in] fd The dmabuf file handle
 * \param[in] length The size of the memory region
 *
 * The \a fd dmabuf file handle is duplicated and stored. The caller may close
 * the original file handle.
 *
 * \return 0 on success or a negative error code otherwise
 */
int Plane::setDmabuf(int fd, unsigned int length)
{
	if (fd < 0) {
		LOG(Buffer, Error) << "Invalid dmabuf fd provided";
		return -EINVAL;
	}

	if (fd_ != -1) {
		close(fd_);
		fd_ = -1;
	}

	fd_ = dup(fd);
	if (fd_ == -1) {
		int ret = -errno;
		LOG(Buffer, Error)
			<< "Failed to duplicate dmabuf: " << strerror(-ret);
		return ret;
	}

	length_ = length;

	return 0;
}

/**
 * \brief Map the plane memory data to a CPU accessible address
 *
 * The file descriptor to map the memory from must be set by a call to
 * setDmaBuf() before calling this function.
 *
 * \sa setDmaBuf()
 *
 * \return 0 on success or a negative error code otherwise
 */
int Plane::mmap()
{
	void *map;

	if (mem_)
		return 0;

	map = ::mmap(NULL, length_, PROT_READ | PROT_WRITE, MAP_SHARED, fd_, 0);
	if (map == MAP_FAILED) {
		int ret = -errno;
		LOG(Buffer, Error)
			<< "Failed to mmap plane: " << strerror(-ret);
		return ret;
	}

	mem_ = map;

	return 0;
}

/**
 * \brief Unmap any existing CPU accessible mapping
 *
 * Unmap the memory mapped by an earlier call to mmap().
 *
 * \return 0 on success or a negative error code otherwise
 */
int Plane::munmap()
{
	int ret = 0;

	if (mem_)
		ret = ::munmap(mem_, length_);

	if (ret) {
		ret = -errno;
		LOG(Buffer, Warning)
			<< "Failed to unmap plane: " << strerror(-ret);