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
  40 struct 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  */
  64 int 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  */
  70 int bounce_buffer_stop(struct bounce_buffer *state);
  71
  72 #endif