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Linux/include/linux/dma-contiguous.h

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  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 #include <linux/device.h>
 57 
 58 struct cma;
 59 struct page;
 60 
 61 #ifdef CONFIG_DMA_CMA
 62 
 63 extern struct cma *dma_contiguous_default_area;
 64 
 65 static inline struct cma *dev_get_cma_area(struct device *dev)
 66 {
 67         if (dev && dev->cma_area)
 68                 return dev->cma_area;
 69         return dma_contiguous_default_area;
 70 }
 71 
 72 static inline void dev_set_cma_area(struct device *dev, struct cma *cma)
 73 {
 74         if (dev)
 75                 dev->cma_area = cma;
 76 }
 77 
 78 static inline void dma_contiguous_set_default(struct cma *cma)
 79 {
 80         dma_contiguous_default_area = cma;
 81 }
 82 
 83 void dma_contiguous_reserve(phys_addr_t addr_limit);
 84 
 85 int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
 86                                        phys_addr_t limit, struct cma **res_cma,
 87                                        bool fixed);
 88 
 89 /**
 90  * dma_declare_contiguous() - reserve area for contiguous memory handling
 91  *                            for particular device
 92  * @dev:   Pointer to device structure.
 93  * @size:  Size of the reserved memory.
 94  * @base:  Start address of the reserved memory (optional, 0 for any).
 95  * @limit: End address of the reserved memory (optional, 0 for any).
 96  *
 97  * This function reserves memory for specified device. It should be
 98  * called by board specific code when early allocator (memblock or bootmem)
 99  * is still activate.
100  */
101 
102 static inline int dma_declare_contiguous(struct device *dev, phys_addr_t size,
103                                          phys_addr_t base, phys_addr_t limit)
104 {
105         struct cma *cma;
106         int ret;
107         ret = dma_contiguous_reserve_area(size, base, limit, &cma, true);
108         if (ret == 0)
109                 dev_set_cma_area(dev, cma);
110 
111         return ret;
112 }
113 
114 struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
115                                        unsigned int order);
116 bool dma_release_from_contiguous(struct device *dev, struct page *pages,
117                                  int count);
118 
119 #else
120 
121 static inline struct cma *dev_get_cma_area(struct device *dev)
122 {
123         return NULL;
124 }
125 
126 static inline void dev_set_cma_area(struct device *dev, struct cma *cma) { }
127 
128 static inline void dma_contiguous_set_default(struct cma *cma) { }
129 
130 static inline void dma_contiguous_reserve(phys_addr_t limit) { }
131 
132 static inline int dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
133                                        phys_addr_t limit, struct cma **res_cma,
134                                        bool fixed)
135 {
136         return -ENOSYS;
137 }
138 
139 static inline
140 int dma_declare_contiguous(struct device *dev, phys_addr_t size,
141                            phys_addr_t base, phys_addr_t limit)
142 {
143         return -ENOSYS;
144 }
145 
146 static inline
147 struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
148                                        unsigned int order)
149 {
150         return NULL;
151 }
152 
153 static inline
154 bool dma_release_from_contiguous(struct device *dev, struct page *pages,
155                                  int count)
156 {
157         return false;
158 }
159 
160 #endif
161 
162 #endif
163 
164 #endif
165 

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