I hope someone else can help with regard to Poseidon and the camera device protocol but have you considered using a USB SD card reader to access your photos?

Personally, I find it is quicker and easier to open the latch on the bottom of compact cameras, then tap on an SD card, pull it out and insert it into an SD card reader. I can usually do it blindly after a short while whereas I really need to pay attention if I want to correctly orient and then insert a small micro or mini USB plug into a camera.

Many Windows and Mac systems feature built-in SD card readers by default. (Or used to at least.) But even if you have to buy an external one as you would for use with MorphOS, they are luckily very inexpensive.

At the very least, it is good to own an SD card reader as a backup in case you cannot seem to find the correct camera cable when you need it.