Re: [REGRESSION] Right touchpad button disabled on Dell 7750

On Fri, 18 Mar 2022 14:07:40 +0100,
José Expósito wrote:

Hi Takashi,

Thanks for reporting the regression here.

On Fri, Mar 18, 2022 at 12:42:31PM +0100, Takashi Iwai wrote:

quoted

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?

A couple of days ago another user with the same laptop (Dell Precision
7550 or 7750) emailed me to report the issue and I sent him a patch for
testing.

I he confirms that the patch works, I'll send it to the mailing list.

I believe that your analysis of the regression is correct and I think
that we'd need to add a quirk for the device.

In case you want to have a look to the patch, I added it to this
libinput [1] report.

Great, I'll try to build and ask the reporter to test with the patch.

Thanks!


Takashi

Thanks,
Jose

[1] https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/726#note_1303623