Re: [RFC PATCH v1 1/1] ACPI: PM: s2idle: Add lps0_screen_off sysfs interface

[Rafael J. Wysocki]

On Tue, Dec 2, 2025 at 5:36 AM Dmitry Osipenko
<dmitry.osipenko@xxxxxxxxxxxxx> wrote:
>
> Add `/sys/power/lps0_screen_off` interface to allow userspace to control
> Display OFF/ON DSM notifications at runtime.

Why?

> Writing "1" to this file triggers the OFF notification, and "0" triggers the ON notification.
>
> Userspace should write "1" after turning off all physical and remote
> displays. It should write "0" before turning on any of displays.

This sets a limitation on the correct/expected usage of this
interface.  How can the kernel ensure that the limitation is taken
into account?  In principle, it should not allow OFF to be triggered
if any displays are "on", for example.

And what exactly do you mean by "turning off a display".  Cutting
power from it or something else?