debcrafters-packages team mailing list archive

[Nick Rosbrook <2110585@xxxxxxxxxxxxxxxxxx>]

This is easy to fix in the devel series.

For SRU purposes, we need a specific test plan, using some specific
hardware (that I don't have) by the sounds of it. If you're willing to
draw up a test plan and do the testing once a fix is in $series-
proposed, we can definitely SRU this.

Though, given 6.15 is not in any stable Ubuntu releases yet, we can't
really start that process yet.

** Changed in: systemd (Ubuntu Questing)
       Status: New => Triaged

** Changed in: systemd (Ubuntu Questing)
   Importance: Undecided => Medium

** Changed in: systemd (Ubuntu Questing)
     Assignee: (unassigned) => Nick Rosbrook (enr0n)

** Tags added: systemd-sru-next

** Tags added: dcr-incoming

-- 
You received this bug notification because you are a member of
Debcrafters packages, which is subscribed to systemd in Ubuntu.
https://bugs.launchpad.net/bugs/2110585

Title:
  Stop using 'actual_brightness' in systemd

Status in systemd package in Ubuntu:
  Triaged
Status in systemd source package in Noble:
  New
Status in systemd source package in Questing:
  Triaged

Bug description:
  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.

  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.

  This has been fixed in upstream systemd in this commit:
  https://github.com/systemd/systemd/commit/9a224c307b36610e3675390eb2620e74d0f4efb0

  This should be backported to any Ubuntu release that adopts kernel
  6.15 or later.  That means that this should be fixed in Questing,
  followed by backported to Noble because Noble will get OEM and HWE
  kernels that are newer.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/2110585/+subscriptions