New: hid_magicmouse: Bluetooth battery reporting stuck at 4% for Apple Magic Trackpad (USB-C) on Linux 7.0.0.22-generic

https://bugzilla.kernel.org/show_bug.cgi?id=221681

            Bug ID: 221681
           Summary: hid_magicmouse: Bluetooth battery reporting stuck at
                    4% for Apple Magic Trackpad (USB-C) on Linux
                    7.0.0.22-generic
           Product: Drivers
           Version: 2.5
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: Bluetooth
          Assignee: [email protected]
          Reporter: [email protected]
        Regression: No

The hid_magicmouse driver incorrectly reports battery level as 4% for the Apple Magic Trackpad (USB-C) when connected over Bluetooth. The value appears to be a hardcoded default — it never updates, and no battery-related activity appears in dmesg after the device connects.

This is distinct from the Magic Trackpad 2 USB battery fix merged before Linux 7.0-rc3. That fix does not appear to cover the Bluetooth path.

DEVICE
Model: Apple Inc. Magic Trackpad (USB-C)
Serial: d0:c0:50:b8:66:86
Connect: Bluetooth HID v3.19 (UUID 0x1124, classic BT, not BLE)

KERNEL
7.0.0-22-generic (Ubuntu 26.04 LTS)
Driver: hid_magicmouse
Module:
/lib/modules/7.0.0-22-generic/kernel/drivers/hid/hid-magicmouse.ko.zst
srcversion: CB57FC5C3E5315DB93BD466

SYMPTOMS
/sys/class/power_supply/hid-d0:c0:50:b8:66:86-battery/capacity: 4 upower reports: percentage 4%, warning-level: critical, state: discharging upower updated timestamp is current (not stale/1970 epoch)

dmesg on connect shows NO battery-related output from magicmouse driver:

    [129671.910588] hid-generic 0005:004C:0324.004E: unknown main item tag 0x0
    [129671.910684] input: Hunter's Magic Trackpad Mouse as
/devices/virtual/misc/uhid/0005:004C:0324.004E/input/input164
    [129671.910779] input: Hunter's Magic Trackpad as
/devices/virtual/misc/uhid/0005:004C:0324.004E/input/input165
    [129671.910822] hid-generic 0005:004C:0324.004E: input,hidraw7: BLUETOOTH
HID v3.19 Mouse [Hunter's Magic Trackpad] on 88:63:df:8a:6c:87
    [129672.078299] magicmouse 0005:004C:0324.004E: unknown main item tag 0x0
    [129672.078384] input: Apple Inc. Magic Trackpad as
/devices/virtual/misc/uhid/0005:004C:0324.004E/input/input166
    [129672.078443] magicmouse 0005:004C:0324.004E: input,hidraw7: BLUETOOTH

HID v3.19 Mouse [Hunter's Magic Trackpad] on 88:63:df:8a:6c:87

No "battery" string appears anywhere in dmesg output filtered for magic|magicmouse|hid_magic|hid|bluetooth|battery.

POWER SUPPLY UEVENT
POWER_SUPPLY_NAME=hid-d0:c0:50:b8:66:86-battery
POWER_SUPPLY_TYPE=Battery
POWER_SUPPLY_STATUS=Discharging
POWER_SUPPLY_PRESENT=1
POWER_SUPPLY_ONLINE=1
POWER_SUPPLY_CAPACITY=4

NOTES
- The device is rechargeable and was not actually at 4% (trackpad functions normally with no low-battery behavior)
- bluetoothctl does not show a Battery Percentage line, which is expected for HID-over-BT classic devices (not a regression)
- /sys/kernel/debug/hid/0005:004C:0324.004E/rdesc was not accessible
- lsmod confirms hid_magicmouse is loaded and bound to the device

EXPECTED
Battery level is polled from device and reported accurately in /sys/class/power_supply/.../capacity

ACTUAL
Capacity stuck at 4% from connect time, never updated. Driver emits no battery-related log output.

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