#ifdef CONFIG_HAVE_GENERIC_DMA_COHERENT
/* * These two functions are only for dma allocator. * Don't use them in device drivers. */ int dma_alloc_from_coherent(struct device *dev, ssize_t size, dma_addr_t *dma_handle, void **ret);
(...中略...) #else #define dma_alloc_from_coherent(dev, size, handle, ret) (0)
(...中略...) #endif