los_vm_iomap.h

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/*
 * Copyright (c) 2013-2019 Huawei Technologies Co., Ltd. All rights reserved.
 * Copyright (c) 2020-2021 Huawei Device Co., Ltd. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of
 *    conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list
 *    of conditions and the following disclaimer in the documentation and/or other materials
 *    provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors may be used
 *    to endorse or promote products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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 */
 
#ifndef __LOS_VM_IOMAP_H__
#define __LOS_VM_IOMAP_H__
 
#include "los_typedef.h"
#include "los_vm_zone.h"
 
#ifdef __cplusplus
#if __cplusplus
extern "C" {
#endif /* __cplusplus */
#endif /* __cplusplus */
 
/**
 * @brief 
 * @verbatim
    DMA，全称Direct Memory Access，即直接存储器访问。
    DMA传输将数据从一个地址空间复制到另一个地址空间，提供在外设和存储器之间或者存储器和存储器之间的高速数据传输。
    DMA的作用就是实现数据的直接传输，而去掉了传统数据传输需要CPU寄存器参与的环节，主要涉及四种情况的数据传输，
    但本质上是一样的，都是从内存的某一区域传输到内存的另一区域（外设的数据寄存器本质上就是内存的一个存储单元）
 * @endverbatim
 */
 
enum DmaMemType { 
    DMA_CACHE,  ///< 有缓存的DMA
    DMA_NOCACHE ///< 无缓存的DMA
};
 
/* thread safety */
VOID *LOS_DmaMemAlloc(DMA_ADDR_T *dmaAddr, size_t size, size_t align, enum DmaMemType type);
VOID LOS_DmaMemFree(VOID *vaddr);
DMA_ADDR_T LOS_DmaVaddrToPaddr(VOID *vaddr);
 
#ifdef __cplusplus
#if __cplusplus
}
#endif /* __cplusplus */
#endif /* __cplusplus */
 
#endif /* __LOS_VM_IOMAP_H__ */