RE: No touchscreen driver for Dell Inspiron 15 7558
Actually to add, the driver does claim that this touchscreen is an egalax touchscreen. So the driver is definitely the closest step so far. I may have just configured something wrong, but I am not sure what.
There is no Touch Screen device in device manager, but the driver does come up with this.
The hardware tab also mentions that the touch screen is resistive and has a firmware version of '2.1'