[Bug 220678] New: XPS 9440 ALS value spikes

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=220678

            Bug ID: 220678
           Summary: XPS 9440 ALS value spikes
           Product: Drivers
           Version: 2.5
          Hardware: Intel
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: IIO
          Assignee: drivers_iio@kernel-bugs.kernel.org
          Reporter: boliverworK@gmail.com
        Regression: No

# Dell XPS 9440: Ambient Light Sensor wildly incorrect values

## Summary
Ambient light sensor reports increasingly erratic values over time, spiking
from ~15 lux to millions. Worsens with uptime, clears on reboot - suggests
driver state corruption.

## System Info
- **Model**: Dell XPS 9440
- **OS**: Fedora-based (Project Bluefin)
- **Kernel**: [INSERT: uname -r]
- **Device**: `/sys/bus/iio/devices/iio:device0` (name: "als")
- **Sensor Hub**: Intel ISH (hid-sensor-hub 001F:8087:0AC2)

## Problem
Raw kernel values from `/sys/bus/iio/devices/iio:device0/in_illuminance_raw`:
```
Normal: 15000
Spike:  1596251
Normal: 15000
Spike:  778328
```

Progressively worsens without reboot. Scale factor constant at 0.001.

## Logs
```
iio-sensor-prox[1502]: Buffer '/dev/iio:device0' did not have data within 0.5s
iio-sensor-prox[1502]: Invalid bitmask entry for
/sys/devices/LNXSYSTM:00/.../event7
```

## Verification
Raw kernel IIO values spike (not just userspace). Bug is in ISH kernel driver.

## Impact
Function key backlight and screen brightness flicker unpredictably.

## Workaround
```bash
sudo systemctl mask iio-sensor-proxy
```

## Notes
Progressive degradation pattern suggests ISH driver state corruption or memory
leak. May affect other Dell XPS models with Intel ISH.

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