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Marek Vasutb660df32012-08-26 15:19:06 +00001/*
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
Stephen Warren84d35b22012-11-06 11:27:29 +000028#include <linux/types.h>
29
Marek Vasutb660df32012-08-26 15:19:06 +000030/*
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
Stephen Warren84d35b22012-11-06 11:27:29 +000056struct 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
Marek Vasutb660df32012-08-26 15:19:06 +000073/**
74 * bounce_buffer_start() -- Start the bounce buffer session
Stephen Warren84d35b22012-11-06 11:27:29 +000075 * state: stores state passed between bounce_buffer_{start,stop}
Marek Vasutb660df32012-08-26 15:19:06 +000076 * data: pointer to buffer to be aligned
77 * len: length of the buffer
Marek Vasutb660df32012-08-26 15:19:06 +000078 * flags: flags describing the transaction, see above.
79 */
Stephen Warren84d35b22012-11-06 11:27:29 +000080int bounce_buffer_start(struct bounce_buffer *state, void *data,
81 size_t len, unsigned int flags);
Marek Vasutb660df32012-08-26 15:19:06 +000082/**
83 * bounce_buffer_stop() -- Finish the bounce buffer session
Stephen Warren84d35b22012-11-06 11:27:29 +000084 * state: stores state passed between bounce_buffer_{start,stop}
Marek Vasutb660df32012-08-26 15:19:06 +000085 */
Stephen Warren84d35b22012-11-06 11:27:29 +000086int bounce_buffer_stop(struct bounce_buffer *state);
Marek Vasutb660df32012-08-26 15:19:06 +000087
88#endif