Attached is another version of this patch - I like this more because instead of additional parameter for Kc length there is now dedicated function.
When I tried to use updated API I quickly realized that we rarely need to have key length explicitly: algorithm implementations know it already for obvious reasons. Hence I think function is better than parameter.
Looking forward to the LIBVERSION update. We can also merge cipher implementation a5/3 a5/4, gea3, gea4 at the same time which would use this new API. This way we would have more features to warrant such update.
cheers, Max.