Edit File: dma-contiguous.h
#ifndef __LINUX_CMA_H #define __LINUX_CMA_H /* * Contiguous Memory Allocator for DMA mapping framework * Copyright (c) 2010-2011 by Samsung Electronics. * Written by: * Marek Szyprowski <m.szyprowski@samsung.com> * Michal Nazarewicz <mina86@mina86.com> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation; either version 2 of the * License or (at your optional) any later version of the license. */ /* * Contiguous Memory Allocator * * The Contiguous Memory Allocator (CMA) makes it possible to * allocate big contiguous chunks of memory after the system has * booted. * * Why is it needed? * * Various devices on embedded systems have no scatter-getter and/or * IO map support and require contiguous blocks of memory to * operate. They include devices such as cameras, hardware video * coders, etc. * * Such devices often require big memory buffers (a full HD frame * is, for instance, more then 2 mega pixels large, i.e. more than 6 * MB of memory), which makes mechanisms such as kmalloc() or * alloc_page() ineffective. * * At the same time, a solution where a big memory region is * reserved for a device is suboptimal since often more memory is * reserved then strictly required and, moreover, the memory is * inaccessible to page system even if device drivers don't use it. * * CMA tries to solve this issue by operating on memory regions * where only movable pages can be allocated from. This way, kernel * can use the memory for pagecache and when device driver requests * it, allocated pages can be migrated. * * Driver usage * * CMA should not be used by the device drivers directly. It is * only a helper framework for dma-mapping subsystem. * * For more information, see kernel-docs in drivers/base/dma-contiguous.c */ #ifdef __KERNEL__ struct cma; struct page; struct device; #ifdef CONFIG_DMA_CMA /* * There is always at least global CMA area and a few optional device * private areas configured in kernel .config. */ #define MAX_CMA_AREAS (1 + CONFIG_CMA_AREAS) extern struct cma *dma_contiguous_default_area; static inline struct cma *dev_get_cma_area(struct device *dev) { if (dev && dev->cma_area) return dev->cma_area; return dma_contiguous_default_area; } static inline void dev_set_cma_area(struct device *dev, struct cma *cma) { if (dev) dev->cma_area = cma; } static inline void dma_contiguous_set_default(struct cma *cma) { dma_contiguous_default_area = cma; } void dma_contiguous_reserve(phys_addr_t addr_limit); int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base, phys_addr_t limit, struct cma **res_cma); /** * dma_declare_contiguous() - reserve area for contiguous memory handling * for particular device * @dev: Pointer to device structure. * @size: Size of the reserved memory. * @base: Start address of the reserved memory (optional, 0 for any). * @limit: End address of the reserved memory (optional, 0 for any). * * This function reserves memory for specified device. It should be * called by board specific code when early allocator (memblock or bootmem) * is still activate. */ static inline int dma_declare_contiguous(struct device *dev, phys_addr_t size, phys_addr_t base, phys_addr_t limit) { struct cma *cma; int ret; ret = dma_contiguous_reserve_area(size, base, limit, &cma); if (ret == 0) dev_set_cma_area(dev, cma); return ret; } struct page *dma_alloc_from_contiguous(struct device *dev, size_t count, unsigned int order); bool dma_release_from_contiguous(struct device *dev, struct page *pages, int count); #else #define MAX_CMA_AREAS (0) static inline struct cma *dev_get_cma_area(struct device *dev) { return NULL; } static inline void dev_set_cma_area(struct device *dev, struct cma *cma) { } static inline void dma_contiguous_set_default(struct cma *cma) { } static inline void dma_contiguous_reserve(phys_addr_t limit) { } static inline int dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base, phys_addr_t limit, struct cma **res_cma) { return -ENOSYS; } static inline int dma_declare_contiguous(struct device *dev, phys_addr_t size, phys_addr_t base, phys_addr_t limit) { return -ENOSYS; } static inline struct page *dma_alloc_from_contiguous(struct device *dev, size_t count, unsigned int order) { return NULL; } static inline bool dma_release_from_contiguous(struct device *dev, struct page *pages, int count) { return false; } #endif #endif #endif