Linux kernel mirror (for testing)
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linux
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
56struct cma;
57struct page;
58struct device;
59
60#ifdef CONFIG_DMA_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
68extern struct cma *dma_contiguous_default_area;
69
70static inline struct cma *dev_get_cma_area(struct device *dev)
71{
72 if (dev && dev->cma_area)
73 return dev->cma_area;
74 return dma_contiguous_default_area;
75}
76
77static inline void dev_set_cma_area(struct device *dev, struct cma *cma)
78{
79 if (dev)
80 dev->cma_area = cma;
81}
82
83static inline void dma_contiguous_set_default(struct cma *cma)
84{
85 dma_contiguous_default_area = cma;
86}
87
88void dma_contiguous_reserve(phys_addr_t addr_limit);
89
90int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
91 phys_addr_t limit, struct cma **res_cma);
92
93/**
94 * dma_declare_contiguous() - reserve area for contiguous memory handling
95 * for particular device
96 * @dev: Pointer to device structure.
97 * @size: Size of the reserved memory.
98 * @base: Start address of the reserved memory (optional, 0 for any).
99 * @limit: End address of the reserved memory (optional, 0 for any).
100 *
101 * This function reserves memory for specified device. It should be
102 * called by board specific code when early allocator (memblock or bootmem)
103 * is still activate.
104 */
105
106static inline int dma_declare_contiguous(struct device *dev, phys_addr_t size,
107 phys_addr_t base, phys_addr_t limit)
108{
109 struct cma *cma;
110 int ret;
111 ret = dma_contiguous_reserve_area(size, base, limit, &cma);
112 if (ret == 0)
113 dev_set_cma_area(dev, cma);
114
115 return ret;
116}
117
118struct page *dma_alloc_from_contiguous(struct device *dev, int count,
119 unsigned int order);
120bool dma_release_from_contiguous(struct device *dev, struct page *pages,
121 int count);
122
123#else
124
125#define MAX_CMA_AREAS (0)
126
127static inline struct cma *dev_get_cma_area(struct device *dev)
128{
129 return NULL;
130}
131
132static inline void dev_set_cma_area(struct device *dev, struct cma *cma) { }
133
134static inline void dma_contiguous_set_default(struct cma *cma) { }
135
136static inline void dma_contiguous_reserve(phys_addr_t limit) { }
137
138static inline int dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
139 phys_addr_t limit, struct cma **res_cma) {
140 return -ENOSYS;
141}
142
143static inline
144int dma_declare_contiguous(struct device *dev, phys_addr_t size,
145 phys_addr_t base, phys_addr_t limit)
146{
147 return -ENOSYS;
148}
149
150static inline
151struct page *dma_alloc_from_contiguous(struct device *dev, int count,
152 unsigned int order)
153{
154 return NULL;
155}
156
157static inline
158bool dma_release_from_contiguous(struct device *dev, struct page *pages,
159 int count)
160{
161 return false;
162}
163
164#endif
165
166#endif
167
168#endif