I²C is a Philips Inter IC Bus invented decades ago. But it was not used in PC at the beginning. At least not at OS (not even DOS) level. Beside that a lot of ICs are talk I²C and so some of them are used in some motherboards too. Temperature sensors f.i. Said that, I think you should not concentrate on a bus or the bus protocol (I²C), you wanna support for a specific device. I²C can address more then 100 different device addresses on the same bus. Moreover each one speaks a specific control set (registers) which you have to know how to program and read.
What I wanna say is you don't need to understand (program) I²C only, you need the exact register settings of the specific devices. Let's say you need a device driver for your specific touch. But you also need to find a way how YOUR Bios is able to talk to this device. There are no standardizes ways in PC (BIOS) to talk to I²C devices (AFAIK). You have to find out where is the I²C bus master integrated in your Notebook. Is it in the south bridge or the north bridge (no clue if this even exists in new PCs) or if there is on connected via USB hub, or via the legacy (ISA) interface which seem to exist even in new processor designs although most of them do not make ISA available as a socket?
That said, I've designed in and programmed numerous I²C devices outside PCs. I also programmed them with PCs via parallel port and with own build in PC ISA cards. But I don't know how some specific sensors or other devices in notebooks are connected to the PC hardware. Nor did I ever saw standard BIOS calls to support something like that.
