bouncebuf.h

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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Generic bounce buffer implementation
 */
 
#ifndef __COMMONLIB_STORAGE_BOUNCEBUF_H__
#define __COMMONLIB_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_UP((uintptr_t)__##name, DMA_MINALIGN)
#ifndef ARCH_DMA_MINALIGN
#define ARCH_DMA_MINALIGN (DMA_MINALIGN)
#endif
 
#endif // __COMMONLIB_STORAGE_BOUNCEBUF_H__