2 * Generic bounce buffer implementation
4 * Copyright (C) 2012 Marek Vasut <marex@denx.de>
6 * See file CREDITS for list of people who contributed to this
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.
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.
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,
25 #ifndef __INCLUDE_BOUNCEBUF_H__
26 #define __INCLUDE_BOUNCEBUF_H__
28 #include <linux/types.h>
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
37 #define GEN_BB_READ (1 << 0)
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.
45 #define GEN_BB_WRITE (1 << 1)
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.
54 #define GEN_BB_RW (GEN_BB_READ | GEN_BB_WRITE)
56 struct bounce_buffer {
57 /* Copy of data parameter passed to start() */
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.
65 /* Copy of len parameter passed to start() */
67 /* DMA-aligned buffer length */
69 /* Copy of flags parameter passed to start() */
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.
80 int bounce_buffer_start(struct bounce_buffer *state, void *data,
81 size_t len, unsigned int flags);
83 * bounce_buffer_stop() -- Finish the bounce buffer session
84 * state: stores state passed between bounce_buffer_{start,stop}
86 int bounce_buffer_stop(struct bounce_buffer *state);