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

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Message-ID: <hyvpl4gvxc6h2r3itfofjduwb3vpobyo7a7z6g3zapzscqtafh@ixsd4amyljva>
Date: Thu, 26 Jun 2025 12:40:47 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: 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 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?

Thanks.

-- 
Dmitry