MDL_SEG_SIZE
#define MDL_SIZE (MAXPHYS / MDL_SEG_SIZE + 1) /* no hardware limit? */
if (bus_dmamap_create(esc->sc_dmat, MAXPHYS, MDL_SIZE, MDL_SEG_SIZE,
MDL_SEG_SIZE, BUS_DMA_NOWAIT, &esc->sc_xfermap)) {
if ((*dmasize / MDL_SEG_SIZE) > MDL_SIZE)