]>
Commit | Line | Data |
---|---|---|
c64be2bb MS |
1 | #ifndef __LINUX_CMA_H |
2 | #define __LINUX_CMA_H | |
3 | ||
4 | /* | |
5 | * Contiguous Memory Allocator for DMA mapping framework | |
6 | * Copyright (c) 2010-2011 by Samsung Electronics. | |
7 | * Written by: | |
8 | * Marek Szyprowski <m.szyprowski@samsung.com> | |
9 | * Michal Nazarewicz <mina86@mina86.com> | |
10 | * | |
11 | * This program is free software; you can redistribute it and/or | |
12 | * modify it under the terms of the GNU General Public License as | |
13 | * published by the Free Software Foundation; either version 2 of the | |
14 | * License or (at your optional) any later version of the license. | |
15 | */ | |
16 | ||
17 | /* | |
18 | * Contiguous Memory Allocator | |
19 | * | |
20 | * The Contiguous Memory Allocator (CMA) makes it possible to | |
21 | * allocate big contiguous chunks of memory after the system has | |
22 | * booted. | |
23 | * | |
24 | * Why is it needed? | |
25 | * | |
26 | * Various devices on embedded systems have no scatter-getter and/or | |
27 | * IO map support and require contiguous blocks of memory to | |
28 | * operate. They include devices such as cameras, hardware video | |
29 | * coders, etc. | |
30 | * | |
31 | * Such devices often require big memory buffers (a full HD frame | |
32 | * is, for instance, more then 2 mega pixels large, i.e. more than 6 | |
33 | * MB of memory), which makes mechanisms such as kmalloc() or | |
34 | * alloc_page() ineffective. | |
35 | * | |
36 | * At the same time, a solution where a big memory region is | |
37 | * reserved for a device is suboptimal since often more memory is | |
38 | * reserved then strictly required and, moreover, the memory is | |
39 | * inaccessible to page system even if device drivers don't use it. | |
40 | * | |
41 | * CMA tries to solve this issue by operating on memory regions | |
42 | * where only movable pages can be allocated from. This way, kernel | |
43 | * can use the memory for pagecache and when device driver requests | |
44 | * it, allocated pages can be migrated. | |
45 | * | |
46 | * Driver usage | |
47 | * | |
48 | * CMA should not be used by the device drivers directly. It is | |
49 | * only a helper framework for dma-mapping subsystem. | |
50 | * | |
51 | * For more information, see kernel-docs in drivers/base/dma-contiguous.c | |
52 | */ | |
53 | ||
54 | #ifdef __KERNEL__ | |
55 | ||
56 | struct cma; | |
57 | struct page; | |
58 | struct device; | |
59 | ||
60 | #ifdef CONFIG_CMA | |
61 | ||
62 | /* | |
63 | * There is always at least global CMA area and a few optional device | |
64 | * private areas configured in kernel .config. | |
65 | */ | |
66 | #define MAX_CMA_AREAS (1 + CONFIG_CMA_AREAS) | |
67 | ||
68 | extern struct cma *dma_contiguous_default_area; | |
69 | ||
70 | void dma_contiguous_reserve(phys_addr_t addr_limit); | |
4009793e | 71 | int dma_declare_contiguous(struct device *dev, phys_addr_t size, |
c64be2bb MS |
72 | phys_addr_t base, phys_addr_t limit); |
73 | ||
74 | struct page *dma_alloc_from_contiguous(struct device *dev, int count, | |
75 | unsigned int order); | |
76 | bool dma_release_from_contiguous(struct device *dev, struct page *pages, | |
77 | int count); | |
78 | ||
79 | #else | |
80 | ||
81 | #define MAX_CMA_AREAS (0) | |
82 | ||
83 | static inline void dma_contiguous_reserve(phys_addr_t limit) { } | |
84 | ||
85 | static inline | |
4009793e | 86 | int dma_declare_contiguous(struct device *dev, phys_addr_t size, |
c64be2bb MS |
87 | phys_addr_t base, phys_addr_t limit) |
88 | { | |
89 | return -ENOSYS; | |
90 | } | |
91 | ||
92 | static inline | |
93 | struct page *dma_alloc_from_contiguous(struct device *dev, int count, | |
94 | unsigned int order) | |
95 | { | |
96 | return NULL; | |
97 | } | |
98 | ||
99 | static inline | |
100 | bool dma_release_from_contiguous(struct device *dev, struct page *pages, | |
101 | int count) | |
102 | { | |
103 | return false; | |
104 | } | |
105 | ||
106 | #endif | |
107 | ||
108 | #endif | |
109 | ||
110 | #endif |