If you don't mind, I'll step in and add some more context since I worked on both the feature in 6.14 upstream kernel and the PPD change that supports it.
In earlier kernel versions (such as 6.8 as that's mentioned above) there can only be one vendor driver that binds to ACPI platform profile. However, for some OEM's systems there are multiple drivers that can bind. This situation means a race condition occurs - whichever driver gets there first binds to the ACPI platform profile. Depending upon what the driver does we can end up with a case that the value reported by the kernel doesn't change everything it should and thus the value reported by the kernel and consumed by PPD and GNOME for the power slider position reported is not accurate. To accommodate this behavior the ACPI platform profile core code has been changed to a class interface that drivers register into. Multiple drivers can register into this class interface. However this has a side effect that two drivers can claim different positions. For example; if the amd-pmf driver is in power-saver but the dell-pc driver is in performance than what do you advertise for /sys/firmware/acpi/platform_profile? This is why a new string 'custom' was introduced. It makes it clear this is an undefined position. PPD had to be modified to account for this new string. If PPD isn't modified then the system will be in an undefined power state. The Dell systems that prompted this SRU have a BIOS option that configures the user selectable thermal tables which are read by the dell-pc driver. Depending upon what the setting is configured as it's possible to boot up with the two drivers having different values and then the power slider being in an undefined position. FTR - I am not at all worried about risk with this SRU. It is supporting a new string that only exists in 6.14 or later. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2115041 Title: Can't recognize custom ACPI platform profile To manage notifications about this bug go to: https://bugs.launchpad.net/oem-priority/+bug/2115041/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
