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Marek Szyprowskic64be2b2011-12-29 13:09:51 +01001#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
Aneesh Kumar K.Vf825c732013-07-02 11:15:15 +053060#ifdef CONFIG_DMA_CMA
Marek Szyprowskic64be2b2011-12-29 13:09:51 +010061
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
70void dma_contiguous_reserve(phys_addr_t addr_limit);
Vitaly Andrianov40097932012-12-05 09:29:25 -050071int dma_declare_contiguous(struct device *dev, phys_addr_t size,
Marek Szyprowskic64be2b2011-12-29 13:09:51 +010072 phys_addr_t base, phys_addr_t limit);
73
74struct page *dma_alloc_from_contiguous(struct device *dev, int count,
75 unsigned int order);
76bool dma_release_from_contiguous(struct device *dev, struct page *pages,
77 int count);
78
79#else
80
81#define MAX_CMA_AREAS (0)
82
83static inline void dma_contiguous_reserve(phys_addr_t limit) { }
84
85static inline
Vitaly Andrianov40097932012-12-05 09:29:25 -050086int dma_declare_contiguous(struct device *dev, phys_addr_t size,
Marek Szyprowskic64be2b2011-12-29 13:09:51 +010087 phys_addr_t base, phys_addr_t limit)
88{
89 return -ENOSYS;
90}
91
92static inline
93struct page *dma_alloc_from_contiguous(struct device *dev, int count,
94 unsigned int order)
95{
96 return NULL;
97}
98
99static inline
100bool 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