grcan_ring_add
rd = grcan_ring_add(rd, GRCAN_MSG_SIZE, dma->rx.size);
grcan_ring_add(txwr, GRCAN_MSG_SIZE, dma->tx.size));
return grcan_ring_add(a, size - b, size);
priv->eskbp = grcan_ring_add(priv->eskbp, GRCAN_MSG_SIZE,
txrd = grcan_ring_add(txrd, GRCAN_MSG_SIZE, dma->tx.size);