MAX_NR_DEVFNS
nr_devfns = min(nr_devfns, (unsigned int)MAX_NR_DEVFNS - devfn_from);
dev->dma_alias_mask = bitmap_zalloc(MAX_NR_DEVFNS, GFP_KERNEL);
for_each_set_bit(devfn, pdev->dma_alias_mask, MAX_NR_DEVFNS) {