For 24.04, I backported it because the original patch could not be applied directly.
** Patch added: "systemd_255.4-1ubuntu8.11.debdiff" https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/2110585/+attachment/5891167/+files/systemd_255.4-1ubuntu8.11.debdiff -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to systemd in Ubuntu. https://bugs.launchpad.net/bugs/2110585 Title: [SRU] Stop using 'actual_brightness' in systemd Status in OEM Priority Project: Triaged Status in systemd package in Ubuntu: Fix Released Status in systemd source package in Noble: Incomplete Status in systemd source package in Plucky: Incomplete Status in systemd source package in Questing: Fix Released Bug description: [Impact] At shutdown time systemd will record the most recently used brightness value and then attempt to restore it the next boot. In order to do this; it currently will read the 'actual_brightness' value and use that to save. This normally works fine; but GPU drivers don't always show the same value in 'brightness' and 'actual_brightness' meaning that the wrong value may be restored the next boot. This problem is very prominently found on AMD APUs starting with kernel 6.15 due to a new feature called "custom brightness curves". Custom brightness curves are brightness values programmed by an OEM in the firmware to make the panel behave optimally. The 'actual_brightness' of some 'brightness' values will be lower. The same issue can occur on systems using "panel power savings" which behaves similarly. For example if the brightness a user requested was 150, the actual_brightness might be 130. So the next boot the brightness will be "set" to 130, but the actual brightness might be 115. If the user reboots again it will be set to 115 for the next boot but the actual brightness might be 100. That is this gets worse and worse each reboot cycle until the system eventually boots up at minimum brightness. [Test Plan] Verify brightness save/restore works properly on Intel UMA, AMD UMA, and either I+N or A+N systems. [Where problems could occur] If a driver relies upon actual_brightness rather than brightness (which is against kernel API [1] then the brightness might no longer be saved and restored properly. [1] https://origin.kernel.org/doc/html/next/admin-guide/abi- stable.html#abi-sys-class-backlight-backlight-actual-brightness [Other Info] This has been fixed in upstream systemd in this commit: https://github.com/systemd/systemd/commit/9a224c307b36610e3675390eb2620e74d0f4efb0 It's been brought into stable systemd releases carried by other distros as well. No regressions have been reported upstream that I'm aware of. To manage notifications about this bug go to: https://bugs.launchpad.net/oem-priority/+bug/2110585/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
