tty3270_line_increment
tp->line_view_start = tty3270_line_increment(tp, tp->line_view_start, 1);
tp->line_write_start = tty3270_line_increment(tp, tp->line_write_start, 1);
return tp->screen + tty3270_line_increment(tp, tp->line_write_start, num);
return tp->screen + tty3270_line_increment(tp, tp->line_view_start, num - tp->nr_up);