[RFC PATCH v1 0/1] ACPI: s2idle: Add /sys/power/lps0_screen_off

[Dmitry Osipenko <dmitry.osipenko@collabora.com>]

Introduce the `/sys/power/lps0_screen_off` sysfs interface, enabling
userspace control over ACPI LPS0 Display Off/On notifications [1].

These notifications are a part of a Modern Standby [2]. The Display Off
notification signals the firmware when all displays (physical and remote)
are off, allowing it to enter lower power states that makes device pretend
it has been suspended while the system remains operational.

Future work will involve integrating this new sysfs control support into
userspace services like power-profiles-daemon, adding a new `idle_screen_off`
inhibitor type to logind and updating power managers with the new
functionality that may improve power savings for idling devices.

Display notifications will allow to support "resume to a dark mode"
feature where the device wakes briefly, performs actions, and then
re-enters into suspended state.

[1] https://uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf
[2] https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/modern-standby-firmware-notifications

Dmitry Osipenko (1):
  ACPI: PM: s2idle: Add lps0_screen_off sysfs interface

 Documentation/ABI/testing/sysfs-power |  13 +++
 drivers/acpi/x86/s2idle.c             | 149 +++++++++++++++++++++++---
 2 files changed, 145 insertions(+), 17 deletions(-)

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2.51.1