include/bouncebuf.h

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2 /*
   3  * Generic bounce buffer implementation
   4  *
   5  * Copyright (C) 2012 Marek Vasut <marex@denx.de>
   6  */
   7
   8 #ifndef __INCLUDE_BOUNCEBUF_H__
   9 #define __INCLUDE_BOUNCEBUF_H__
  10
  11 #include <linux/types.h>
  12
  13 /*
  14  * GEN_BB_READ -- Data are read from the buffer eg. by DMA hardware.
  15  * The source buffer is copied into the bounce buffer (if unaligned, otherwise
  16  * the source buffer is used directly) upon start() call, then the operation
  17  * requiring the aligned transfer happens, then the bounce buffer is lost upon
  18  * stop() call.
  19  */
  20 #define GEN_BB_READ     (1 << 0)
  21 /*
  22  * GEN_BB_WRITE -- Data are written into the buffer eg. by DMA hardware.
  23  * The source buffer starts in an undefined state upon start() call, then the
  24  * operation requiring the aligned transfer happens, then the bounce buffer is
  25  * copied into the destination buffer (if unaligned, otherwise destination
  26  * buffer is used directly) upon stop() call.
  27  */
  28 #define GEN_BB_WRITE    (1 << 1)
  29 /*
  30  * GEN_BB_RW -- Data are read and written into the buffer eg. by DMA hardware.
  31  * The source buffer is copied into the bounce buffer (if unaligned, otherwise
  32  * the source buffer is used directly) upon start() call, then the  operation
  33  * requiring the aligned transfer happens, then the bounce buffer is  copied
  34  * into the destination buffer (if unaligned, otherwise destination buffer is
  35  * used directly) upon stop() call.
  36  */
  37 #define GEN_BB_RW       (GEN_BB_READ | GEN_BB_WRITE)
  38
  39 struct bounce_buffer {
  40         /* Copy of data parameter passed to start() */
  41         void *user_buffer;
  42         /*
  43          * DMA-aligned buffer. This field is always set to the value that
  44          * should be used for DMA; either equal to .user_buffer, or to a
  45          * freshly allocated aligned buffer.
  46          */
  47         void *bounce_buffer;
  48         /* Copy of len parameter passed to start() */
  49         size_t len;
  50         /* DMA-aligned buffer length */
  51         size_t len_aligned;
  52         /* Copy of flags parameter passed to start() */
  53         unsigned int flags;
  54 };
  55
  56 /**
  57  * bounce_buffer_start() -- Start the bounce buffer session
  58  * state:       stores state passed between bounce_buffer_{start,stop}
  59  * data:        pointer to buffer to be aligned
  60  * len:         length of the buffer
  61  * flags:       flags describing the transaction, see above.
  62  */
  63 int bounce_buffer_start(struct bounce_buffer *state, void *data,
  64                         size_t len, unsigned int flags);
  65
  66 /**
  67  * bounce_buffer_start() -- Start the bounce buffer session with external align check function
  68  * state:       stores state passed between bounce_buffer_{start,stop}
  69  * data:        pointer to buffer to be aligned
  70  * len:         length of the buffer
  71  * flags:       flags describing the transaction, see above.
  72  * alignment:   alignment of the newly allocated bounce buffer
  73  * addr_is_aligned: function for checking the alignment instead of the default one
  74  */
  75 int bounce_buffer_start_extalign(struct bounce_buffer *state, void *data,
  76                                  size_t len, unsigned int flags,
  77                                  size_t alignment,
  78                                  int (*addr_is_aligned)(struct bounce_buffer *state));
  79
  80 /**
  81  * bounce_buffer_stop() -- Finish the bounce buffer session
  82  * state:       stores state passed between bounce_buffer_{start,stop}
  83  */
  84 int bounce_buffer_stop(struct bounce_buffer *state);
  85
  86 #endif