#include <linux/dma-mapping.h>/* Set this to 1 if there is a HW IOMMU in the system */int iommu_detected __read_mostly;struct dma_map_ops *dma_ops;EXPORT_SYMBOL(dma_ops);struct dma_map_ops *dma_get_ops(struct device *dev){return dma_ops;}EXPORT_SYMBOL(dma_get_ops);