| 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); |
| 71 | int dma_declare_contiguous(struct device *dev, phys_addr_t size, |
| 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 |
| 86 | int dma_declare_contiguous(struct device *dev, phys_addr_t size, |
| 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 |