linux-kernel - Re: [RFC PATCH v1 1/1] ACPI: PM: s2idle: Add lps0_screen

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJZ5v0hRiA_AFTsBL0Ud5vdDyyqSJcwLtKaVtpYareh4URS_CQ@mail.gmail.com>
Date: Wed, 3 Dec 2025 15:58:48 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Dmitry Osipenko <dmitry.osipenko@...labora.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Mario Limonciello <superm1@...nel.org>, 
	Robert Beckett <bob.beckett@...labora.com>, linux-acpi@...r.kernel.org, 
	kernel@...labora.com, linux-kernel@...r.kernel.org, 
	Sebastian Reichel <sebastian.reichel@...labora.com>, Xaver Hugl <xaver.hugl@...il.com>, 
	Richard Hughes <richard@...hsie.com>, William Jon McCann <mccann@....edu>, 
	"Jaap A . Haitsma" <jaap@...tsma.org>, Benjamin Canou <bookeldor@...il.com>, 
	Bastien Nocera <hadess@...ess.net>, systemd-devel@...ts.freedesktop.org, 
	Lennart Poettering <lennart@...ttering.net>, Antheas Kapenekakis <lkml@...heas.dev>
Subject: Re: [RFC PATCH v1 1/1] ACPI: PM: s2idle: Add lps0_screen_off sysfs interface

On Tue, Dec 2, 2025 at 5:36 AM Dmitry Osipenko
<dmitry.osipenko@...labora.com> 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?