dma_malloc
p = dma_malloc(ess->buf_dmat, ess->bufsz, &physaddr, &ch->map);
ess->stat = dma_malloc(ess->stat_dmat, 3*ess->bufsz, &ess->phys,
static void *dma_malloc(bus_dma_tag_t, u_int32_t, bus_addr_t*,