thank you ....I've opened my eyes to the harsh reality: only Canon knows..... 
This used to be a bigger problem for us. Once a port was done for a particular camera & firmware version, it was still quite a bit of work to create ports for other firmware versions of the same camera model. Thanks to philmoz's code_gen utility (and some of chdk-pt's almost obsolete code matching features) it has become much easier to do.
Recently, if you ask nicely and can get a firmware dump, nafraf will usually create a version for a new firmware.
