[PATCH v1 2/4] acpi/x86: s2idle: handle screen off/on calls outside of suspend sequence

[Antheas Kapenekakis]

Hi,
as noted in the cover letter, I think the connection to DRM is a red herring.

The Display off callback in Windows is always called 5 seconds after
the screen turns off due to inactivity or instantly if the user
presses the power button. Likewise, Display on is called when the
display is about to turn on.

In fact, pressing the powerbutton in Windows no longer suspends the
device. It just locks the session and turns off the screen. Then
Windows can do whatever it wants for however long it wants before
suspending the device. It took me 2 days to realise this, as my dev
unit was updating and it stayed happily on for 10-20 minutes after
pressing the power button when connected to a charger.

I think "Screen Off" is what Microsoft decided to call their
background wakelock state (as it is called in Android). That means
that if there is ever a laptop with an Always On display, it will be
on the "Screen Off" state while the screen is on.

Antheas