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