dma_direct_alloc
vaddr = dma_direct_alloc(dev, size, dma_addr, flag, attrs);
.alloc = dma_direct_alloc,
void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
cpu_addr = dma_direct_alloc(dev, size, dma_handle, flag, attrs);