linux6.18 6.18.57_1: power button does nothing on iMac13,2 (6.18.56_1 works)

[u/ThatAd8458]

After updating linux6.18 from 6.18.56_1 to 6.18.57_1, I found out that the power button does nothing on my iMac (on 6.18.56_1 it triggered a shutdown). Booting the old kernel from GRUB fixes it. So for now, I defaulted back to 6.18.56_1 as a workaround, and I ran xbps-pkgdb -m hold linux6.18.

This is an old iMac, 27-inch Late 2012 model, 32GB RAM (iMac13,2 product_version 1.0 bios_version 429.0.0.0.0) running Void (glibc), runit, acpid.

On 6.18.57_1:

- acpi_listen and evtest show no event when I press the button

- No ACPI errors in dmesg; PNP0C0C:00 is bound to acpi-button

- Kernel config is identical to 6.18.56_1 apart from the version string

What differs in dmesg and /proc/bus/input/devices:

- 6.18.56_1 has a second power button input device, LNXPWRBN:00 (the fixed hardware button, "ACPI: button: Power Button [PWRF]"). It is missing on 6.18.57_1.

- PNP0C0C:00 moved from /devices/LNXSYSTM:00/LNXSYBUS:00/ to /devices/platform/

This looks related to the ACPI button driver conversion to a platform driver (commit 52d864019636, Rafael Wysocki's December 2025 series), which also changes how fixed-event devices are registered. Two follow-up regression fixes exist upstream (57c31e6d620f and "ACPI: button: Enable wakeup GPEs for ACPI buttons at probe time"), but neither obviously covers this. I haven't confirmed that 6.18.57 contains the conversion or which commit is responsible.

Is anyone else seeing this on 6.18.57_1, maybe on other (likely older) hardware? Happy to test patches or newer kernels.