automatic screen brightness never stops adjusting

[robdew]

Had to disable automatic screen brightness because it was constantly going up and down, like it was "hunting" for a setting. If you open the settings panel in the upper right you can watch the brightness slider move up and down randomly.

let me know what other troubleshooting I can do to help or fix.

[jmontleon]

It's not specific to the Pixelbook. I've seen lots of complaints about it.

For example:
https://www.dell.com/community/XPS/XPS-9300-Ubuntu-amp-Adaptive-Brightness-changing-all-the-time/td-p/7515943

At least part of it is https://gitlab.gnome.org/GNOME/gnome-settings-daemon/-/issues/82

But if you're sitting in a dark room the light sensor values will change just by having something brighter or darker on the screen. The sensor values will even vary just sitting in a room doing nothing, so I think there's more to it than just reading every value and adjusting whether instantly or smoothly.

[jmontleon]

If I recall it's something like watch cat /sys/devices/pci0000:00/0000:00:1f.0/PNP0C09:00/GOOG0004:00/cros-ec-dev.1.auto/cros-ec-sensorhub.3.auto/cros-ec-light.18.auto/iio:device2/in_illuminance_input to watch the sensor values and you'll see it jumping all over the place, which is why you're seeing your brightness jump all over.

[jmontleon]

I would be interested to learn a way to calibrate sensor or smooth the readings so it's not like this but I haven't been able to find much other than people suggesting to turn off adaptive brightness. I've even seen people suggesting this for Chrome OS https://chromeunboxed.com/how-to-disable-auto-brightness-on-your-chromebook

[robdew]

I have no reference for what works and doesn't work outside of ChromeOS on the Pixelbook because this is the first guide that has worked for me. I figured it was better to report than ignore.

[jmontleon]

@robdew yup, thank you for the report. I added some notes in case someone else looks, knows better, and can help improve the situation.

[jmontleon]

There's nothing to be done here for this, so I'm going to close this.

There are several PRs and issues in various open/closed states against Gnome that might one day resolve this, for example:
https://gitlab.gnome.org/GNOME/gnome-settings-daemon/-/issues/82
https://gitlab.gnome.org/GNOME/gnome-settings-daemon/-/merge_requests/237

[huang-jy]

Just to make an addition, there's an option in Power settings that allows you to turn off autoadjusting brightness.

Setting this off stops my screen from going bright and dark randomly based on the light level.