+/*
+ * The only reason to have several buffers is to accommodate assumptions
+ * in line disciplines. They ask for empty space amount, receive our URB size,
+ * and proceed to issue several 1-character writes, assuming they will fit.
+ * The very first write takes a complete URB. Fortunately, this only happens
+ * when processing onlcr, so we only need 2 buffers. These values must be
+ * powers of 2.
+ */