Bug 2401613

The touchpad on LapBook Pro laptops with HTIX5288:00 0911:5288 (vendor 0911, product 5288) exhibits incorrect finger detection in libinput. The kernel correctly reports finger counts via BTN_TOOL_FINGER, BTN_TOOL_DOUBLETAP, BTN_TOOL_TRIPLETAP, and BTN_TOOL_QUADTAP events (verified with evtest), but libinput consistently interprets these as one fewer finger than actually present.
Technical verification:

Kernel events are correct: evtest shows BTN_TOOL_DOUBLETAP when 2 fingers touch, BTN_TOOL_TRIPLETAP for 3 fingers, etc.
libinput behavior is wrong: 1 finger produces no/erratic pointer movement, 2 fingers act as single-finger pointer movement, 3 fingers trigger two-finger scrolling

Device information:

Device name: HTIX5288:00 0911:5288 Touchpad
Vendor/Product: 0911:5288
Bus: i2c (I2C-HID)
Physical size: 110x63mm
Max coordinates: X: 2628, Y: 1332
Resolution: X: 24 units/mm, Y: 21 units/mm
Laptop: LapBook Pro (DMI: "Manufacturer: Not Specified, Product Name: LapBook Pro")

Comparison with working configuration:
The same hardware works correctly on Puppy Linux using xf86-input-synaptics driver, which uses pressure-based finger detection (Synaptics Finger threshold: 25, 30, 0). This suggests libinput's BTN_TOOL_* event interpretation logic has incorrect assumptions for this specific touchpad variant.
Failed workaround attempts:

libinput quirks file - quirks system not functional on test system
hwdb evdev calibration - caused complete touchpad failure (no movement)
hid_multitouch kernel module parameters - none available

Reproducible: Always

Steps to Reproduce:
1. Install Linux distribution with libinput (tested on Fedora Silverblue 42, GNOME Wayland)
2. Use laptop with HTIX5288:00 0911:5288 touchpad (LapBook Pro or similar)
3. Touch touchpad with 1 finger and attempt to move pointer
4. Touch touchpad with 2 fingers and attempt to scroll
5. Verify kernel events: sudo evtest /dev/input/eventX | grep BTN_TOOL (replace X with touchpad event number)
Actual Results:
1 finger: Cursor jumps erratically or doesn't move
2 fingers: Pointer movement (single-finger behavior)
3 fingers: Two-finger scrolling
4 fingers: Three-finger gesture
Kernel correctly reports: BTN_TOOL_FINGER (1), BTN_TOOL_DOUBLETAP (2), BTN_TOOL_TRIPLETAP (3), BTN_TOOL_QUADTAP (4)

Expected Results:
1 finger: Pointer movement
2 fingers: Two-finger scrolling
3 fingers: Three-finger gesture
4 fingers: Four-finger gesture
libinput should correctly interpret the kernel's BTN_TOOL_* events

Additional Information:
**evtest output samples:**

One finger touch:
```
Event: type 1 (EV_KEY), code 325 (BTN_TOOL_FINGER), value 1
```

Two finger touch:
```
Event: type 1 (EV_KEY), code 325 (BTN_TOOL_FINGER), value 0
Event: type 1 (EV_KEY), code 333 (BTN_TOOL_DOUBLETAP), value 1
```

Three finger touch:
```
Event: type 1 (EV_KEY), code 333 (BTN_TOOL_DOUBLETAP), value 0
Event: type 1 (EV_KEY), code 334 (BTN_TOOL_TRIPLETAP), value 1
```

**libinput device info:**
```
Device:                  HTIX5288:00 0911:5288 Touchpad
Kernel:                  /dev/input/event9
Size:                    110x63mm
Capabilities:            pointer gesture
Tap-to-click:            disabled
Scroll methods:          *two-finger edge
Click methods:           *button-areas clickfinger
Disable-w-typing:        enabled
```

**Existing libinput quirk for related devices:**
The file `/usr/share/libinput/30-vendor-synaptics.quirks` contains:
```
[Synaptics 0911:5288 Touchpad]
MatchUdevType=touchpad
MatchName=* 0911:5288 Touchpad
AttrEventCode=-BTN_RIGHT
```
This matches other 0911:5288 variants (SYNA3602, ALPS0001, PCT2342) but not HTIX5288:00 prefix.

**Observed anomalies:**
During testing, evtest occasionally showed coordinate values far beyond valid range (43007, 46079, 63489 vs max 2628, 1332). These may be palm rejection artifacts but don't appear to be the root cause, as BTN_TOOL_* events remain correct.

**System information:**
- Distribution: Fedora Silverblue 40/41
- Desktop: GNOME Wayland
- libinput version: (latest in Fedora repos as of 2025-10-05)
- Kernel: (recent 6.x series)