LXR linux/include/linux/dma-contiguous.h

   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
 169