include/bouncebuf.h

   1 /*
   2  * Generic bounce buffer implementation
   3  *
   4  * Copyright (C) 2012 Marek Vasut <marex@denx.de>
   5  *
   6  * See file CREDITS for list of people who contributed to this
   7  * project.
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License as
  11  * published by the Free Software Foundation; either version 2 of
  12  * the License, or (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, write to the Free Software
  21  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  22  * MA 02111-1307 USA
  23  */
  24
  25 #ifndef __INCLUDE_BOUNCEBUF_H__
  26 #define __INCLUDE_BOUNCEBUF_H__
  27
  28 #include <linux/types.h>
  29
  30 /*
  31  * GEN_BB_READ -- Data are read from 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 lost upon
  35  * stop() call.
  36  */
  37 #define GEN_BB_READ     (1 << 0)
  38 /*
  39  * GEN_BB_WRITE -- Data are written into the buffer eg. by DMA hardware.
  40  * The source buffer starts in an undefined state upon start() call, then the
  41  * operation requiring the aligned transfer happens, then the bounce buffer is
  42  * copied into the destination buffer (if unaligned, otherwise destination
  43  * buffer is used directly) upon stop() call.
  44  */
  45 #define GEN_BB_WRITE    (1 << 1)
  46 /*
  47  * GEN_BB_RW -- Data are read and written into the buffer eg. by DMA hardware.
  48  * The source buffer is copied into the bounce buffer (if unaligned, otherwise
  49  * the source buffer is used directly) upon start() call, then the  operation
  50  * requiring the aligned transfer happens, then the bounce buffer is  copied
  51  * into the destination buffer (if unaligned, otherwise destination buffer is
  52  * used directly) upon stop() call.
  53  */
  54 #define GEN_BB_RW       (GEN_BB_READ | GEN_BB_WRITE)
  55
  56 struct bounce_buffer {
  57         /* Copy of data parameter passed to start() */
  58         void *user_buffer;
  59         /*
  60          * DMA-aligned buffer. This field is always set to the value that
  61          * should be used for DMA; either equal to .user_buffer, or to a
  62          * freshly allocated aligned buffer.
  63          */
  64         void *bounce_buffer;
  65         /* Copy of len parameter passed to start() */
  66         size_t len;
  67         /* DMA-aligned buffer length */
  68         size_t len_aligned;
  69         /* Copy of flags parameter passed to start() */
  70         unsigned int flags;
  71 };
  72
  73 /**
  74  * bounce_buffer_start() -- Start the bounce buffer session
  75  * state:       stores state passed between bounce_buffer_{start,stop}
  76  * data:        pointer to buffer to be aligned
  77  * len:         length of the buffer
  78  * flags:       flags describing the transaction, see above.
  79  */
  80 int bounce_buffer_start(struct bounce_buffer *state, void *data,
  81                         size_t len, unsigned int flags);
  82 /**
  83  * bounce_buffer_stop() -- Finish the bounce buffer session
  84  * state:       stores state passed between bounce_buffer_{start,stop}
  85  */
  86 int bounce_buffer_stop(struct bounce_buffer *state);
  87
  88 #endif