[REGRESSION] Right touchpad button disabled on Dell 7750

Hi,

we received a bug report about the regression of the touchpad on Dell 7750 laptop, the right touchpad button is disabled on recent kernels: https://bugzilla.suse.com/show_bug.cgi?id=1197243

Note that it's a physical button, not a virtual clickpad button.

The regression seems introduced by the upstream commit 37ef4c19b4c659926ce65a7ac709ceaefb211c40 ("Input: clear BTN_RIGHT/MIDDLE on buttonpads") that was backported to stable 5.16.x kernel.

The device is managed by hid-multitouch driver, and the further investigation revealed that it's rather an incorrectly recognized buttonpad property; namely, ID_DG_BUTTONTYPE reports it being 0 = clickable touchpad although it's not. I built a test kernel to ignore this check and it was confirmed to make the right button working again by the reporter.

Is this check really correct in general? Or do we need some device-specific quirk?

thanks,

Takashi