LXR uboot/include/bouncebuf.h

   1/*
   2 * Generic bounce buffer implementation
   3 *
   4 * Copyright (C) 2012 Marek Vasut <marex@denx.de>
   5 *
   6 * SPDX-License-Identifier:     GPL-2.0+
   7 */
   8
   9#ifndef __INCLUDE_BOUNCEBUF_H__
  10#define __INCLUDE_BOUNCEBUF_H__
  11
  12#include <linux/types.h>
  13
  14/*
  15 * GEN_BB_READ -- Data are read from the buffer eg. by DMA hardware.
  16 * The source buffer is copied into the bounce buffer (if unaligned, otherwise
  17 * the source buffer is used directly) upon start() call, then the operation
  18 * requiring the aligned transfer happens, then the bounce buffer is lost upon
  19 * stop() call.
  20 */
  21#define GEN_BB_READ     (1 << 0)
  22/*
  23 * GEN_BB_WRITE -- Data are written into the buffer eg. by DMA hardware.
  24 * The source buffer starts in an undefined state upon start() call, then the
  25 * operation requiring the aligned transfer happens, then the bounce buffer is
  26 * copied into the destination buffer (if unaligned, otherwise destination
  27 * buffer is used directly) upon stop() call.
  28 */
  29#define GEN_BB_WRITE    (1 << 1)
  30/*
  31 * GEN_BB_RW -- Data are read and written into the buffer eg. by DMA hardware.
  32 * The source buffer is copied into the bounce buffer (if unaligned, otherwise
  33 * the source buffer is used directly) upon start() call, then the  operation
  34 * requiring the aligned transfer happens, then the bounce buffer is  copied
  35 * into the destination buffer (if unaligned, otherwise destination buffer is
  36 * used directly) upon stop() call.
  37 */
  38#define GEN_BB_RW       (GEN_BB_READ | GEN_BB_WRITE)
  39
  40struct bounce_buffer {
  41        /* Copy of data parameter passed to start() */
  42        void *user_buffer;
  43        /*
  44         * DMA-aligned buffer. This field is always set to the value that
  45         * should be used for DMA; either equal to .user_buffer, or to a
  46         * freshly allocated aligned buffer.
  47         */
  48        void *bounce_buffer;
  49        /* Copy of len parameter passed to start() */
  50        size_t len;
  51        /* DMA-aligned buffer length */
  52        size_t len_aligned;
  53        /* Copy of flags parameter passed to start() */
  54        unsigned int flags;
  55};
  56
  57/**
  58 * bounce_buffer_start() -- Start the bounce buffer session
  59 * state:       stores state passed between bounce_buffer_{start,stop}
  60 * data:        pointer to buffer to be aligned
  61 * len:         length of the buffer
  62 * flags:       flags describing the transaction, see above.
  63 */
  64int bounce_buffer_start(struct bounce_buffer *state, void *data,
  65                        size_t len, unsigned int flags);
  66/**
  67 * bounce_buffer_stop() -- Finish the bounce buffer session
  68 * state:       stores state passed between bounce_buffer_{start,stop}
  69 */
  70int bounce_buffer_stop(struct bounce_buffer *state);
  71
  72#endif
  73