Allen_Hung@Dell.com writes:

Dell - Internal Use - Confidential
Hi Ben,

We have just confirmed the touchpad on Latitude E7470 is a PS/2
device, not an I2C-HID input device. The code you listed is common
among many Dell products and the value of SDS0 should be provided
somewhere (I can't find it out) to specify a PS/2 device.

Thanks Allen,

I rather suspected this; I suppose it's probably hard to find I2C-HID
hardware that integrates a touchstick. This explains why SDS0 is 0 on my
hardware.

In this case I suppose this is yet another Alps device? I've tried
bringing it up with all of the recent Alps protocols supported by the
alps.ko driver but sadly nothing seems to emit multitouch events, so
it seems likely that there is yet another protocol variant waiting to be
implemented. Is there any chance you could see whether Alps might now be
more willing to provide protocol documentation? If not, perhaps there's
a Linux binary driver available?

Cheers,

- Ben