This fix works for me.

System: ASUS X302LA, Linux Mint 22.3 (based on Ubuntu 24.04 Noble)

Symptoms with kernel 7.0.0-28-generic:

Brightness keys had no effect
No backlight after resuming from suspend (black screen)

Workaround used prior to testing the fix: adding
i915.enable_dpcd_backlight=0 to the GRUB kernel command line restored
normal behavior.

Testing method: proposed pocket not enabled via apt/sources.list;
instead, manually downloaded and installed the following packages from
this bug's Launchpad page via dpkg:

linux-hwe-7.0-headers-7.0.0-31 (15 MB)
linux-headers-7.0.0-31-generic (4.0 MB)
linux-image-7.0.0-31-generic (16 MB)
linux-modules-7.0.0-31-generic (161 MB)

Result: Booted into kernel 7.0.0-31-generic without the
i915.enable_dpcd_backlight=0 workaround. Brightness keys work correctly
and backlight resumes normally after suspend. Re-tested kernel
7.0.0-28-generic (workaround removed) to confirm the regression is still
present there, ruling out any coincidence.

tags: verification-done-noble

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https://bugs.launchpad.net/bugs/2161309

Title:
  Backlight regression

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