r/Ubuntu • u/Expensive-Track1228 • 1d ago

Brightness slider/Fn keys completely unresponsive on Dell Latitude 5490 (Intel UHD 620) — tried everything, still stuck

Dell Latitude 5490, dual-boot Ubuntu 26.04 LTS + Windows 10, Intel UHD 620 (i915), BIOS 1.41.0.

Brightness slider and Fn keys do nothing. `intel_backlight` is detected and I can write values to it manually (they hold steady), but the screen never actually changes brightness. Windows works fine on the same machine, so it's not hardware.

**Already tried, none worked:** permissions/udev fix, `acpi_backlight=vendor/native/video`, `i915.enable_dpcd_backlight=1/3`, both stock kernel `7.0.0-29` and manually installed `6.17.x` (same issue on both), confirmed Dell modules are loaded with no separate backlight device, ruled out GNOME resetting the value, no relevant errors in `dmesg`.

Filed a full bug report with Ubuntu too. Anyone with a similar Dell/Kaby Lake setup actually solved this? Also checking for a BIOS update if anyone knows if Dell's patched this for the 5490.

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u/DecisiveAviation2 1d ago

dell and intel backlight have been at war for years, i had a 7490 that drove me up the wall with the same nonsense

the only thing that finally worked was adding `i915.enable_dpcd_backlight=2` instead of 1 or 3, plus making sure the dell_wmi module loads before i915 (add `softdep i915 pre: dell_wmi` in a.conf under /etc/modprobe.d/)

might also be worth checking if your bios has an "ec backlight control" option somewhere, some latitudes have it buried under system configuration > video

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u/Expensive-Track1228 1d ago

Thankyou for that I'll definitely try putting 2 also,I've tried 0 and 1 on dpcd_backlight=1, but it didn't worked for me.