ATMEL_SERIAL_RINGSIZE
ATMEL_SERIAL_RINGSIZE)
ring->tail = (ring->tail + 1) & (ATMEL_SERIAL_RINGSIZE - 1);
BUILD_BUG_ON(ATMEL_SERIAL_RINGSIZE & (ATMEL_SERIAL_RINGSIZE - 1));
if (!CIRC_SPACE(ring->head, ring->tail, ATMEL_SERIAL_RINGSIZE))
ring->head = (ring->head + 1) & (ATMEL_SERIAL_RINGSIZE - 1);