Raspberry Pi 500+: power button detected but no KEY_POWER events generated (kernel 6.12.x)

[4Misi]

Describe the bug

On Raspberry Pi 500+, running Raspberry Pi OS (Trixie / Debian 13) with kernel 6.12.x,
the built-in power button is detected by the kernel but does not generate any
KEY_POWER input events.

The input device appears correctly under /dev/input, but pressing the power button
produces no events at all. As a result, systemd-logind never receives a power key
event and no shutdown or power action occurs.

This appears to be a kernel-level regression affecting the pwr_button input device
on Raspberry Pi 500+.

Steps to reproduce the behaviour

1. Boot Raspberry Pi 500+ with Raspberry Pi OS (Trixie).
2. Verify the power button input device exists:
   ls -l /dev/input/by-path | grep pwr
3. Run:
   sudo evtest /dev/input/event5 (or the corresponding pwr_button event device)
4. Press the physical power button.

No events are generated.

Device (s)

Raspberry Pi 500+

System

OS: Raspberry Pi OS (Trixie / Debian 13)
Architecture: aarch64

Kernel:
Linux raspberrypi 6.12.47+rpt-rpi-2712 #1 SMP PREEMPT Debian 1:6.12.47-1+rpt1~bookworm aarch64

Firmware:
(vcgenmd version output can be provided if required)

Logs

evtest output:

Input device name: "pwr_button"
Supported events:
Event type 1 (EV_KEY)
Event code 116 (KEY_POWER)

Pressing the power button produces no output.

Additional context

• The input device is present and registered:
  input:input5 "pwr_button"
• systemd-logind is using default configuration (HandlePowerKey=poweroff).
• User-space configuration and triggerhappy were ruled out.
• The issue persists after restoring a clean system configuration.

This strongly suggests a kernel or driver regression rather than a user-space issue.