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

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Message-ID: <exmgckzoakt2ncsdphqvymcadon7k6tl36a3zvrj2pv23dffps@znq23v3qbcm2>
Date: Thu, 26 Jun 2025 12:28:27 -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 09:18:56PM +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.

Thanks.

-- 
Dmitry