linux-kernel - Re: [PATCH v3 4/4] Input: Don't send fake button presses to wake system

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Message-ID: <CAJZ5v0i20Qjxw=GAc-PTHL8U5kq-zsDR2fWcp9dbrkF6PbRBqw@mail.gmail.com>
Date: Fri, 27 Jun 2025 12:36:07 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Hans de Goede <hansg@...nel.org>, 
	Mario Limonciello <superm1@...nel.org>, Mika Westerberg <westeri@...nel.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	Linus Walleij <linus.walleij@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>, 
	"open list:GPIO ACPI SUPPORT" <linux-gpio@...r.kernel.org>, 
	"open list:GPIO ACPI SUPPORT" <linux-acpi@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>, 
	"open list:INPUT (KEYBOARD, MOUSE, JOYSTICK, TOUCHSCREEN)..." <linux-input@...r.kernel.org>, Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH v3 4/4] Input: Don't send fake button presses to wake system

On Thu, Jun 26, 2025 at 9:40 PM Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
>
> On Thu, Jun 26, 2025 at 09:31:12PM +0200, Rafael J. Wysocki wrote:
> > On Thu, Jun 26, 2025 at 9:28 PM Dmitry Torokhov
> > <dmitry.torokhov@...il.com> wrote:
> > >
> > > On Thu, Jun 26, 2025 at 09:18:56PM +0200, Rafael J. Wysocki wrote:
> > > > On Thu, Jun 26, 2025 at 9:16 PM Hans de Goede <hansg@...nel.org> wrote:
> > > > >
> > > > > Hi,
> > > > >
> > > > > On 26-Jun-25 21:14, Dmitry Torokhov wrote:
> > > > > > On Thu, Jun 26, 2025 at 08:57:30PM +0200, Hans de Goede wrote:
> > > > > >> Hi,
> > > > > >>
> > > > > >> On 26-Jun-25 20:48, Dmitry Torokhov wrote:
> > > > > >>> On Thu, Jun 26, 2025 at 01:20:54PM -0500, Mario Limonciello wrote:
> > > [...]
> > > > > >>>> I want to note this driver works quite differently than how ACPI power
> > > > > >>>> button does.
> > > > > >>>>
> > > > > >>>> You can see in acpi_button_notify() that the "keypress" is only forwarded
> > > > > >>>> when not suspended [1].  Otherwise it's just wakeup event (which is what my
> > > > > >>>> patch was modeling).
> > > > > >>>>
> > > > > >>>> https://github.com/torvalds/linux/blob/v6.16-rc3/drivers/acpi/button.c#L461
> > > > > >>>> [1]
> > > > > >>>
> > > > > >>> If you check acpi_button_resume() you will see that the events are sent
> > > > > >>> from there. Except that for some reason they chose to use KEY_WAKEUP and
> > > > > >>> not KEY_POWER, oh well. Unlike acpi button driver gpio_keys is used on
> > > > > >>> multiple other platforms.
> > > > > >>
> > > > > >> Interesting, but the ACPI button code presumably only does this on resume
> > > > > >> for a normal press while the system is awake it does use KEY_POWER, right ?
> > > > > >
> > > > > > Yes. It is unclear to me why they chose to mangle the event on wakeup,
> > > > > > it does not seem to be captured in the email discussions or in the patch
> > > > > > description.
> > > > >
> > > > > I assume they did this to avoid the immediate re-suspend on wakeup by
> > > > > power-button issue. GNOME has a workaround for this, but I assume that
> > > > > some userspace desktop environments are still going to have a problem
> > > > > with this.
> > > >
> > > > It was done for this reason IIRC, but it should have been documented
> > > > more thoroughly.
> > >
> > > I assert that it should not have been done and instead dealt with in
> > > userspace. There are numerous drivers in the kernel emitting
> > > KEY_POWER. Let userspace decide how to handle this, what keys to ignore,
> > > what keys to process and when.
> >
> > Please see my last message in this thread (just sent) and see the
> > changelog of commit 16f70feaabe9 ("ACPI: button: trigger wakeup key
> > events").
> >
> > This appears to be about cases when no event would be signaled to user
> > space at all (power button wakeup from ACPI S3).
>
> Ahh, in S3 we do not know if we've been woken up with Sleep or Power
> button, right? So we can not send the "right" event code and use
> "neutral" KEY_WAKEUP for both. Is this right?

Yes, it is, AFAICS.