On Fri, Sep 04, 2020 at 10:16:51AM +0200, Benjamin Tissoires wrote:
Hi,
On Tue, Aug 11, 2020 at 11:15 AM Coiby Xu <coiby.xu@xxxxxxxxx> 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
Thank you for the advice! I have exactly adopted this approach by looking
at commit e9287099ba6539bccb20cd791269186f3ae28b85
("HID: rmi: Add support for the touchpad in the Razer Blade 14 laptop")
as an example.
My previous email is a bit misleading because 0x04F3 is the vendor code
of ELAN while hid-rmi is for the Synaptics touchpad. And actually this
laptop model of Lenovo Legion-5 15ARH05 is shipped with both kinds of
touchpads,
- for the Synaptics touchpad, hid-rmi could almost handle it perfectly
except the clicking is not sensitive enough. I need to let my finger
linger on the touchpad for a while. I notice when I click on the touchpad,
an HID report would be received by hid-recorder. But evtest couldn't receive
any EV_ event. If hid-multitouch is handling the device, the cursor
won't move but 2-4 finger touching events could still be received by
evtest.
- for the ELAN touchpad, only HID reporters can be read and parsed by
hid-core then two input devices (mouse and touchpad) could created by
hid-multitouch as seen from /proc/bus/input/devices. But hid-recorder
could never get any HID report.
AFAIU, isn't hid-multitouch supposed to be the implementation of Windows
Precision Touchpad? And since Precision touchpad is mandatory for
Windows 10 notebooks and this laptop model of Lenovo Legion-5 15ARH05
seem to have been certificated by Windows 10, does it mean by theory
hid-multiouch could handle these two touchpad devices?
Anyway, it seems I need to install Windows Driver Kit to capture&analyze
HID reports to see what's happening. Or do you have any suggestion?
--
Best regards,
Coiby
