Re: [PATCH 0/1] Do not map BTN_RIGHT/MIDDLE on buttonpads

On Wed, Nov 24, 2021 at 10:39:02AM +0100, Benjamin Tissoires wrote:

Hi José,

On Tue, Nov 23, 2021 at 8:12 PM José Expósito [off-list ref] wrote:

quoted

Hi all,

Historically, libinput has relayed on the INPUT_PROP_BUTTONPAD property
to detect buttonpads.

Since buttonpads are expected to have only one button (BTN_LEFT),
recently we added a new rule to detect buttonpads: Where a touchpad
maps the BTN_RIGHT bit, libinput assumes it is NOT a buttonpad.

However, this change leaded to several false possitives, so we ended up
reverting it. For more context:
https://gitlab.freedesktop.org/libinput/libinput/-/issues/704

And for a full list of affected hardware, HID reports and bug reports
please see:
https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/726

My understanding is that buttonpads should not map BTN_RIGHT and/or
BTN_MIDDLE and to avoid it I would like to fix the required drivers.

As long as udev intrinsic is happy with it (and it correctly tags the
touchpad as ID_INPUT_something), I'm fine with it.

fwiw, udev's builtin input-id touchpad check is
  ABS_X && ABS_Y && BTN_TOOL_FINGER && !BTN_TOOL_PEN && !INPUT_PROP_DIRECT
it doesn't care about the actual buttons so this patch wouldn't affect it.

Also, you might want to point at the specification regarding button
pads: https://docs.microsoft.com/en-us/windows-hardware/design/component-guidelines/touchpad-windows-precision-touchpad-collection#device-capabilities-feature-report

The way I read it: if the device exports the Button type value
feature, and it is 0 or 1 (click-pad or pressure-pad), there should
not be discrete buttons.

Yeah, it sounds like there *should* not be any buttons but 
There is nothing to explicitly forbid extra buttons for click/pressurepads
which is probably how those devices get past the windows driver
implementation.

Cheers,
   Peter