After the recent improvements to the older Sony printers (Most notably, the UP-CR10L is now confirmed working after a bunch of little modifications!) I decided to take another look at some more recent (but not necessarily new) models:
They're a diverse bunch, but share a common data format and communications protocol built on top of what appears to be standard HP-PJL.
I believe I've successfully figured out the data format for all of these models, and written the intial backend parser. The next step is to write the Gutenprint rasterizer code, but anything beyond that will require access to one or more of these models so I can obtain details about the communication protocol they use, and of course, test my code out.
I still don't know how to obtain media type and counter information out of the older Sony models (UP-DR150/UP-DR200/UP-CR10L) too, so without someone out there willing to perform sniffs of Sony's Windows or OSX drivers doing their thing (or send me a printer!) I'm not likely to be able to progress beyond the current state of affairs.
There are a bunch of other Sony models, mostly consumer-focused, that may be worth trying to support too, but I'd rather spend my time on models that are still commercially relevant. Of course, hardware in hand trumps everything else!
Anway. Back to the bit mines..