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/*
* Generic bounce buffer implementation
*
* Copyright (C) 2012 Marek Vasut <marex@denx.de>
* Copyright 2013 Google Inc. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#ifndef __DRIVERS_STORAGE_BOUNCEBUF_H__
#define __DRIVERS_STORAGE_BOUNCEBUF_H__
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
/*
* GEN_BB_READ -- Data are read from the buffer eg. by DMA hardware.
* The source buffer is copied into the bounce buffer (if unaligned, otherwise
* the source buffer is used directly) upon start() call, then the operation
* requiring the aligned transfer happens, then the bounce buffer is lost upon
* stop() call.
*/
#define GEN_BB_READ (1 << 0)
/*
* GEN_BB_WRITE -- Data are written into the buffer eg. by DMA hardware.
* The source buffer starts in an undefined state upon start() call, then the
* operation requiring the aligned transfer happens, then the bounce buffer is
* copied into the destination buffer (if unaligned, otherwise destination
* buffer is used directly) upon stop() call.
*/
#define GEN_BB_WRITE (1 << 1)
/*
* GEN_BB_RW -- Data are read and written into the buffer eg. by DMA hardware.
* The source buffer is copied into the bounce buffer (if unaligned, otherwise
* the source buffer is used directly) upon start() call, then the operation
* requiring the aligned transfer happens, then the bounce buffer is copied
* into the destination buffer (if unaligned, otherwise destination buffer is
* used directly) upon stop() call.
*/
#define GEN_BB_RW (GEN_BB_READ | GEN_BB_WRITE)
struct bounce_buffer {
/* Copy of data parameter passed to start() */
void *user_buffer;
/*
* DMA-aligned buffer. This field is always set to the value that
* should be used for DMA; either equal to .user_buffer, or to a
* freshly allocated aligned buffer.
*/
void *bounce_buffer;
/* Copy of len parameter passed to start() */
size_t len;
/* DMA-aligned buffer length */
size_t len_aligned;
/* Copy of flags parameter passed to start() */
unsigned int flags;
};
/**
* bounce_buffer_start() -- Start the bounce buffer session
* state: stores state passed between bounce_buffer_{start,stop}
* data: pointer to buffer to be aligned
* len: length of the buffer
* flags: flags describing the transaction, see above.
*/
int bounce_buffer_start(struct bounce_buffer *state, void *data,
size_t len, unsigned int flags);
/**
* bounce_buffer_stop() -- Finish the bounce buffer session
* state: stores state passed between bounce_buffer_{start,stop}
*/
int bounce_buffer_stop(struct bounce_buffer *state);
// TODO(hungte) Eliminate the alignment stuff below and replace them with a
// better and centralized way to handler non-cache/aligned memory.
// Helper macros for alignment.
#define DMA_MINALIGN (64)
#define ROUND(a, b) (((a) + (b) - 1) & ~((b) - 1))
#define ALLOC_CACHE_ALIGN_BUFFER(type, name, size) \
char __##name[ROUND(size * sizeof(type), DMA_MINALIGN) + \
DMA_MINALIGN - 1]; \
type *name = (type *) ALIGN((uintptr_t)__##name, DMA_MINALIGN)
#ifndef ARCH_DMA_MINALIGN
#define ARCH_DMA_MINALIGN (DMA_MINALIGN)
#endif
#endif // __DRIVERS_STORAGE_BOUNCEBUF_H__
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