blob: 5ffa99bc131f8b69be7fabf6e8377d992e3265d0
1 | /* |
2 | * Generic bounce buffer implementation |
3 | * |
4 | * Copyright (C) 2012 Marek Vasut <marex@denx.de> |
5 | * |
6 | * SPDX-License-Identifier: GPL-2.0+ |
7 | */ |
8 | |
9 | #ifndef __INCLUDE_BOUNCEBUF_H__ |
10 | #define __INCLUDE_BOUNCEBUF_H__ |
11 | |
12 | #include <linux/types.h> |
13 | |
14 | /* |
15 | * GEN_BB_READ -- Data are read from the buffer eg. by DMA hardware. |
16 | * The source buffer is copied into the bounce buffer (if unaligned, otherwise |
17 | * the source buffer is used directly) upon start() call, then the operation |
18 | * requiring the aligned transfer happens, then the bounce buffer is lost upon |
19 | * stop() call. |
20 | */ |
21 | #define GEN_BB_READ (1 << 0) |
22 | /* |
23 | * GEN_BB_WRITE -- Data are written into the buffer eg. by DMA hardware. |
24 | * The source buffer starts in an undefined state upon start() call, then the |
25 | * operation requiring the aligned transfer happens, then the bounce buffer is |
26 | * copied into the destination buffer (if unaligned, otherwise destination |
27 | * buffer is used directly) upon stop() call. |
28 | */ |
29 | #define GEN_BB_WRITE (1 << 1) |
30 | /* |
31 | * GEN_BB_RW -- Data are read and written into 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 copied |
35 | * into the destination buffer (if unaligned, otherwise destination buffer is |
36 | * used directly) upon stop() call. |
37 | */ |
38 | #define GEN_BB_RW (GEN_BB_READ | GEN_BB_WRITE) |
39 | |
40 | struct bounce_buffer { |
41 | /* Copy of data parameter passed to start() */ |
42 | void *user_buffer; |
43 | /* |
44 | * DMA-aligned buffer. This field is always set to the value that |
45 | * should be used for DMA; either equal to .user_buffer, or to a |
46 | * freshly allocated aligned buffer. |
47 | */ |
48 | void *bounce_buffer; |
49 | /* Copy of len parameter passed to start() */ |
50 | size_t len; |
51 | /* DMA-aligned buffer length */ |
52 | size_t len_aligned; |
53 | /* Copy of flags parameter passed to start() */ |
54 | unsigned int flags; |
55 | }; |
56 | |
57 | /** |
58 | * bounce_buffer_start() -- Start the bounce buffer session |
59 | * state: stores state passed between bounce_buffer_{start,stop} |
60 | * data: pointer to buffer to be aligned |
61 | * len: length of the buffer |
62 | * flags: flags describing the transaction, see above. |
63 | */ |
64 | int bounce_buffer_start(struct bounce_buffer *state, void *data, |
65 | size_t len, unsigned int flags); |
66 | /** |
67 | * bounce_buffer_stop() -- Finish the bounce buffer session |
68 | * state: stores state passed between bounce_buffer_{start,stop} |
69 | */ |
70 | int bounce_buffer_stop(struct bounce_buffer *state); |
71 | |
72 | #endif |
73 |