Detecting if a laptop is using a i2c/smbus or a ps/2 attached touchpad?

[Hans de Goede <hdegoede@redhat.com>]

Hi Benjamin, et. al.,

I have just merged a patch which adds a couple of DMI quirks to disable
the touchpad on/off functionality of the ideapad-laptop module on some models,
because it is causing issues there.

Patch:      https://lore.kernel.org/platform-driver-x86/20221018095323.14591-1-limanyi@uniontech.com/
Discussion: https://lore.kernel.org/platform-driver-x86/fdceb6d2-c38c-e8ff-4c19-b01521ca46c0@redhat.com/

Rather then using DMI quirks I would prefer to just disable it everywhere
where a i2c-attached touchpad is used. Be it either one only attached to
i2c, or one of the synaptics intertouch thingies. I'm still trying to
figure out why the ideapad-laptop module's touchpad control (which
uses the EC + enabling/disabling the i8042 aux-port) matters for
i2c-attached touchpads at all, so I suspect that intertouch might be
a part of it.

So now I'm wondering if there is some nice way for the ideapad-laptop
code to check if the touchpad is intertouch and/or if it is i2c-attached
only ...

Any ideas?

Regards,

Hans

p.s.

Is it possible that Elan touchpads use something similar to intertouch,
or is that a synaptics thing only (under Linux)  ?