I don't think there are dumb questions. I do think there are lazy questions. I classify a lazy question as a question where the answer is googleable or is documented in a well-known location. If you're a programmer asking me about the implementation of a function and you have no reason not to read it and understand it yourself, I expect you to go read the code, not ask me how it works.
How do you feel when people ask you questions that are googleable or might require a bit of code or documentation reading?