Re: [PATCH v2] HID: multitouch: Fix Yoga Book 9 14IAH10 touchscreen misclassification

[Dave Carey <carvsdriver@gmail.com>]

It's pretty rad.  Have one more patch coming in a bit to fix a trailing 
ghost touch issue.

On 5/12/26 11:39 AM, Jiri Kosina wrote:
> On Mon, 13 Apr 2026, Dave Carey wrote:
>
>> The Lenovo Yoga Book 9 14IAH10 (83KJ) (17EF:6161) firmware includes a
>> HID_DG_TOUCHPAD application collection designed for the Windows inbox HID
>> driver's Win8 PTP touchpad mode.  On Linux the HID_DG_TOUCHSCREEN
>> collections provide the correct direct-touch interface.  The presence of
>> the touchpad collection causes hid-multitouch to misclassify the
>> touchscreen nodes as indirect buttonpads, leaving them non-functional.
>>
>> Within the touchpad collection:
>> - HID_UP_BUTTON usages trigger the touchscreen-with-buttons heuristic
>>    that sets INPUT_MT_POINTER on the touchscreen applications.
>> - The HID_DG_TOUCHPAD application itself sets INPUT_MT_POINTER via
>>    mt_allocate_application(), propagating to all touchscreen nodes.
>> - A HID_DG_BUTTONTYPE feature (report 0x51) returns MT_BUTTONTYPE_CLICKPAD,
>>    setting td->is_buttonpad = true for the entire device.
>>
>> Additionally, the firmware resets if any USB control request arrives while
>> the CDC-ACM interface is initialising (~1.18 s after enumeration).
>> The Win8 compliance blob (0xff00:0xc5) and Contact Count Max feature
>> reports in the touchscreen collections trigger GET_REPORT calls at probe
>> that hit this window.  Surface Switch (0x57) and Button Switch (0x58)
>> feature reports are sent by mt_set_modes() on every input-device open and
>> close, repeatedly hitting this window throughout device lifetime.
>>
>> The firmware also leaves a persistent ghost contact in its contact buffer
>> (contact ID 2, fixed coordinates, tip always asserted) on every enumeration.
>> This ghost occupies a multitouch slot and prevents KWin from seeing a clean
>> finger-lift, causing stuck touch state.  The ghost is cleared when Input
>> Mode is set via HID_REQ_SET_REPORT at probe.
> Oh man, what a device.
> Applied, thanks.
>