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 /*
  29  * GEN_BB_READ -- Data are read from the buffer eg. by DMA hardware.
  30  * The source buffer is copied into the bounce buffer (if unaligned, otherwise
  31  * the source buffer is used directly) upon start() call, then the operation
  32  * requiring the aligned transfer happens, then the bounce buffer is lost upon
  33  * stop() call.
  34  */
  35 #define GEN_BB_READ     (1 << 0)
  36 /*
  37  * GEN_BB_WRITE -- Data are written into the buffer eg. by DMA hardware.
  38  * The source buffer starts in an undefined state upon start() call, then the
  39  * operation requiring the aligned transfer happens, then the bounce buffer is
  40  * copied into the destination buffer (if unaligned, otherwise destination
  41  * buffer is used directly) upon stop() call.
  42  */
  43 #define GEN_BB_WRITE    (1 << 1)
  44 /*
  45  * GEN_BB_RW -- Data are read and written into the buffer eg. by DMA hardware.
  46  * The source buffer is copied into the bounce buffer (if unaligned, otherwise
  47  * the source buffer is used directly) upon start() call, then the  operation
  48  * requiring the aligned transfer happens, then the bounce buffer is  copied
  49  * into the destination buffer (if unaligned, otherwise destination buffer is
  50  * used directly) upon stop() call.
  51  */
  52 #define GEN_BB_RW       (GEN_BB_READ | GEN_BB_WRITE)
  53
  54 #ifdef CONFIG_BOUNCE_BUFFER
  55 /**
  56  * bounce_buffer_start() -- Start the bounce buffer session
  57  * data:        pointer to buffer to be aligned
  58  * len:         length of the buffer
  59  * backup:      pointer to backup buffer (the original value is stored here if
  60  *              needed
  61  * flags:       flags describing the transaction, see above.
  62  */
  63 int bounce_buffer_start(void **data, size_t len, void **backup, uint8_t flags);
  64 /**
  65  * bounce_buffer_stop() -- Finish the bounce buffer session
  66  * data:        pointer to buffer that was aligned
  67  * len:         length of the buffer
  68  * backup:      pointer to backup buffer (the original value is stored here if
  69  *              needed
  70  * flags:       flags describing the transaction, see above.
  71  */
  72 int bounce_buffer_stop(void **data, size_t len, void **backup, uint8_t flags);
  73 #else
  74 static inline int bounce_buffer_start(void **data, size_t len, void **backup,
  75                                         uint8_t flags)
  76 {
  77         return 0;
  78 }
  79
  80 static inline int bounce_buffer_stop(void **data, size_t len, void **backup,
  81                                         uint8_t flags)
  82 {
  83         return 0;
  84 }
  85 #endif
  86
  87 #endif