Re: [PATCH] HID: multitouch: add a quirk to skip set inputmode for 2 new laptops

[Hui Wang <hui.wang@canonical.com>]

On 1/7/21 8:42 PM, Barnabás Pőcze wrote:
> Hi
>
>
> 2021. január 7., csütörtök 12:27 keltezéssel, Hui Wang írta:
>
>> we have 2 latest Thinkpad laptops, the synaptics trackpoint module is
>> connected to i8042 bus and the synaptics touchpad module is on the i2c
>> bus. The trackpoint is driven by input/mouse/trackpoint.c and the
>> touchpad is driven by hid-multitouch.c.
>>
>> They all work well independently, but if users press any buttons of
>> trackpoint and meanwhile move finger on the touchpad, the touchpad
>> can't work, the i2c bus can't generate interrupts even. That is to say
>> the touchpad can't work with trackpoint together, once trackpoint
>> works, the touchpad stops working.
>>
>> The current hid driver parses the device descriptor and selects the
>> hid-multitouch.c and applies the MT_CLS_WIN_8 to the touchpad, I found
>> this issue begins to happen after the driver sets the
>> MT_INPUTMODE_TOUCHPAD to the device, If skipping to set it, the
>> touchpad work well and doesn't have that issue, even after suspend and
>> resume, the touchpad still work well.
>>
>> This touchpad module doesn't support multi inputmodes, and its init
>> mode is set by BIOS already, it is safe to skip to set it again in
>> the kernel driver.
>> [...]
> Assuming I'm not missing anything obvious, a windows precision touchpad
> should revert back to reporting events via its HID compliant mouse collection
> when power cycled or reset by the host[1].
>
> Doesn't that imply that the events will be reported via the mouse collection
> in this case, and that the multi-touch capabilities of the device will not
> be usable? Or am I missing something?
>
>
> [1]: https://docs.microsoft.com/en-us/windows-hardware/design/component-guidelines/windows-precision-touchpad-required-hid-top-level-collections#input-mode-feature-report

Yes, you are right, after applying this patch, the events will be 
reported through mouse collection and some features specific to touchpad 
collection like multi-touch are lost. So this patch is not a correct 
solution, please ignore this patch.

And I found If using the hid-rmi.c to drive this touchpad, it will work 
well, the touchpad and trackpoint could work well together and the 
touchpad has multi-touch capability. But because the report descriptor 
contains an Input item which has the usage HID_DG_CONTACTID, the 
hid->group is set to HID_GROUP_MULTITOUCH, the hid-multitouch.c is 
selected to drive this touchpad.

Is it Okay to do the change below and let hid-rmi.c drive this touchpad?

diff --git a/drivers/hid/hid-rmi.c b/drivers/hid/hid-rmi.c
index 311eee599ce9..58a7529499f5 100644
--- a/drivers/hid/hid-rmi.c
+++ b/drivers/hid/hid-rmi.c
@@ -759,6 +759,7 @@ static const struct hid_device_id rmi_id[] = {
         { HID_USB_DEVICE(USB_VENDOR_ID_PRIMAX, 
USB_DEVICE_ID_PRIMAX_REZEL) },
         { HID_USB_DEVICE(USB_VENDOR_ID_SYNAPTICS, 
USB_DEVICE_ID_SYNAPTICS_ACER_SWITCH5),
                 .driver_data = RMI_DEVICE_OUTPUT_SET_REPORT },
+       { HID_I2C_DEVICE(USB_VENDOR_ID_SYNAPTICS, 0xce57) },
         { HID_DEVICE(HID_BUS_ANY, HID_GROUP_RMI, HID_ANY_ID, HID_ANY_ID) },
         { }
  };

Thanks,

Hui.

>
>
> Regards,
> Barnabás Pőcze
>