The APA102 is probably even simpler, it acts as a 1 byte shift register register per LED and passes the bytes down the chain without needing to really know the total length, there's some special case to latch all the data into the output registers. I'm fond of that design because it needs no timing specific input, you could easily input the data with push buttons if you cared to.
GE Color Effects G-35 Christmas lights from about a decade ago used a similar scheme, except that they boot up in an "enumerate" state and use the first transmission to each figure out their own unique address (or pass the messages down the line). After that, they can each be addressed individually.
