dma.c

来自「优龙2410linux2.6.8内核源代码」· C语言 代码 · 共 37 行

/*
 * Dynamic DMA mapping support.
 *
 * We never have any address translations to worry about, so this
 * is just alloc/free.
 */

#include <linux/types.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/pci.h>
#include <asm/io.h>

void *dma_alloc_coherent(struct device *dev, size_t size,
			   dma_addr_t *dma_handle, int gfp)
{
	void *ret;
	/* ignore region specifiers */
	gfp &= ~(__GFP_DMA | __GFP_HIGHMEM);

	if (dev == NULL || (*dev->dma_mask < 0xffffffff))
		gfp |= GFP_DMA;
	ret = (void *)__get_free_pages(gfp, get_order(size));

	if (ret != NULL) {
		memset(ret, 0, size);
		*dma_handle = virt_to_phys(ret);
	}
	return ret;
}

void dma_free_coherent(struct device *dev, size_t size,
			 void *vaddr, dma_addr_t dma_handle)
{
	free_pages((unsigned long)vaddr, get_order(size));
}