Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx>
Vladimir suggested to add a dummy "return 0" function [1] for the unsupported interface. So, I added this empty callback, will keep the empty callback if no other concern. Thanks.
[1] https://lore.kernel.org/all/b1e1ff88-5bba-4424- bc85-38caa85b831f@xxxxxxxxxx/