[BUG] ACPI INT33D3 ambient light sensor not bound on Intel Lunar Lake (ThinkPad X1 Carbon Gen 13)

[big.block0203@fastmail.com]

Hi,

On a Lenovo ThinkPad X1 Carbon Gen 13 (Intel Lunar Lake), the ACPI
firmware declares an INT33D3 ambient light sensor as present, enabled,
and functional, but no Linux driver binds to it. As a result, no IIO
device is created and no ambient light data is available to userspace
(KDE/GNOME auto-brightness, iio-sensor-proxy, etc.).

I did not find an existing report covering this on Lunar Lake. Apologies
if this duplicates one I missed; pointers welcome.

Hardware
========
- Lenovo ThinkPad X1 Carbon Gen 13
- Intel Core Ultra 7 258V (Lunar Lake, Xe2)
- iGPU: PCI 8086:64a0 (rev 04), subsystem 17aa:2339
- Panel: Samsung Display ATNA40YK20-0 (2.8K OLED)

Software
========
- Fedora Kinoite 44
- kernel 7.0.6-200.fc44.x86_64
- KDE Plasma 6 on Wayland

Symptom
=======
No IIO devices are exposed at all:

    $ ls /sys/bus/iio/devices/
    (empty)
    $ ls /sys/class/iio/
    (empty)

But the ALS is declared in ACPI:

    $ cat /sys/bus/acpi/devices/INT33D3:00/hid
    INT33D3

    $ cat /sys/bus/acpi/devices/INT33D3:00/status
    15

    $ ls /sys/bus/acpi/devices/INT33D3:00/
    cid  hid  modalias  path  physical_node  power  status  subsystem  uevent
    # No `driver` symlink under physical_node — nothing bound.

    $ readlink /sys/bus/acpi/devices/INT33D3:00/physical_node
    ../../../../../../pci0000:00/0000:00:1f.0/PNP0C09:00/INT33D3:00

    $ sudo dmesg | grep -i INT33D3
    (no output — no driver even attempted to probe)

Status 0xf per ACPI spec means: present (bit 0), enabled (bit 1), shown
in UI (bit 2), functional (bit 3). The firmware unambiguously declares
the device as available. dmesg shows no probe attempt and no error.

Other unclaimed firmware-declared devices on this platform (for context)
========================================================================
    INTC1025:00     status=?    driver=NONE
    INTC105D:00     status=15   driver=intel-pinctrl
    INTC105D:01     status=15   driver=intel-pinctrl
    INTC105D:02     status=15   driver=intel-pinctrl
    INTC105D:03     status=15   driver=intel-pinctrl
    INTC105D:04     status=15   driver=intel-pinctrl
    INTC1068:00     status=15   driver=int3400 thermal
    INTC1069:00     status=15   driver=int3403 thermal
    INTC1069:01     status=15   driver=int3403 thermal
    INTC1069:02     status=15   driver=int3403 thermal
    INTC1069:03     status=15   driver=int3403 thermal
    INTC1069:04     status=15   driver=int3403 thermal
    INTC107B:00     status=15   driver=intel-hid
    INTC1092:00     status=0    driver=NONE
    INTC109D:00     status=15   driver=NONE

INTC109D:00 is also present-and-enabled but has no driver bound. Its
function is unknown to me; including it for awareness in case it is
sensor-hub-related and a prerequisite for INT33D3.

INT3519:00 is also present in ACPI but with status=0 (disabled by
firmware), so likely not relevant here.

Expected behavior
==================
An IIO device of class `in_illuminance*` should appear under
/sys/bus/iio/devices/, allowing iio-sensor-proxy and desktop
environments to consume ambient light data for auto-brightness.

Thanks,
big.block