blah.osl:3: error: array of struct are not allowed as parameters
Inside the body of the shader (if I give the array a definite length), it seems ok.
TBH, I need to look at the code and probably dig through past emails. I'm not entirely sure if this is unintentional (some kind of bug) or if there was a reason that parameters, but not ordinary variables, should not allow this. It surprises me seeing it now -- mostly because this seems like a common thing to try and I'm surprised nobody has noticed until now -- but on the other hand, maybe in my old age I'm just forgetting why this was an important limitation.
I'll try to have a better answer for you within a couple days.