What is a well supported touchscreen driver to emulate?

I'll spare the whys and hows of the project behind this but I am working on some hardware that needs to appear to the host Linux machine (Raspberry Pi) as a touchscreen*, ideally one that works over I2C or Serial bus and would be automatically discovered at boot time. So the question is - what are some well supported I2C or Serial touchscreen devices that would be a good choice to emulate in the situation? It ideally wants to be a well-supported & reliable driver so we don't have to do any tinkering with the host linux build to make it work, and simple enough that we don't have to jump through too many hoops on the emulation side either. *= Or similar pointing device like a Wacom tablet I guess would work as it uses X/Y cooridinates rather than "mousey" movements.