[Linux-kernel-mentees] Advice on fixing the bug of MSFT0001:00 04F3:Touchpad being handled by hid_multitouch by mistake
Benjamin Tissoires
benjamin.tissoires at redhat.com
Fri Sep 4 08:16:51 UTC 2020
Hi,
On Tue, Aug 11, 2020 at 11:15 AM Coiby Xu <coiby.xu at gmail.com> wrote:
>
> Hi,
>
> I'm working on a touchpad device issue as reported on
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1887190.
>
> This touchpad device MSFT0001:00 04F3:Touchpad should be handled by
> hid_rmi. But currently hid-core.c chooses hid_multitouch by mistake,
>
> 1. When scanning this device's report descriptor, HID_DG_CONTACTID
> usage is found. Thus group HID_GROUP_MULTITOUCH is assigned to
> the device.
> 2. The flag HID_SCAN_FLAG_MT_WIN_8 is also found. Thus group
> HID_GROUP_MULTITOUCH_WIN_8 is assigned to the device.
> 3. hid-multitouch.c claims handling devices with the group of
> HID_GROUP_MULTITOUCH_WIN_8
>
> static const struct hid_device_id mt_devices[] = {
> /* Generic MT device */
> { HID_DEVICE(HID_BUS_ANY, HID_GROUP_MULTITOUCH, HID_ANY_ID, HID_ANY_ID) },
>
> /* Generic Win 8 certified MT device */
> { .driver_data = MT_CLS_WIN_8,
> HID_DEVICE(HID_BUS_ANY, HID_GROUP_MULTITOUCH_WIN_8,
> HID_ANY_ID, HID_ANY_ID) },
> { }
> };
>
> There are several potential solutions,
> - Let the device vendor fix this problem since this device's report
> descriptor shouldn't have the HID_DG_CONTACTID usage.
> - Make it a special case by setting the device's group to
> HID_GROUP_RMI in hid_scan_report when vendor id and product ID
> are matched.
> - hid-quirks.c seems to be designed to handle special cases, is it
> suitable for this case?
AFAIU, the touchpad doesn't work at all with hid-multitouch. So I
guess the best is to add the VID/PID to hid-quirks.c in
hid_have_special_driver[], and add it to the hid-rmi driver too.
This way, you will ensure hid-rmi will pick up the device all the time.
Cheers,
Benjamin
>
> Can anyone give an advice on which direction I should take? Thank you!
>
> --
> Best regards,
> Coiby
>
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