HDA_DMA_ALIGNMENT
blksz -= blksz % lcm(HDA_DMA_ALIGNMENT, sndbuf_getalign(ch->b));
HDA_DMA_ALIGNMENT, /* alignment */
alignment = roundup2(HDA_DMA_ALIGNMENT, PAGE_SIZE);
alignment = HDA_DMA_ALIGNMENT;
#define HDA_BLK_MIN HDA_DMA_ALIGNMENT