linux-kernel - Re: [PATCH 1/4] Input: Add trackpoint doubletap and system debug info keycodes

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Date: Tue, 9 Apr 2024 14:54:28 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Hans de Goede <hdegoede@...hat.com>
Cc: Mark Pearson <mpearson-lenovo@...ebb.ca>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	ibm-acpi-devel@...ts.sourceforge.net,
	"platform-driver-x86@...r.kernel.org" <platform-driver-x86@...r.kernel.org>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Nitin Joshi1 <njoshi1@...ovo.com>,
	Vishnu Sankar <vsankar@...ovo.com>,
	Peter Hutterer <peter.hutterer@...hat.com>
Subject: Re: [PATCH 1/4] Input: Add trackpoint doubletap and system debug
 info keycodes

On Tue, Apr 09, 2024 at 12:16:04PM +0200, Hans de Goede wrote:
> Hi Dmitry,
> 
> On 4/9/24 2:00 AM, Mark Pearson wrote:
> > Hi Dmitry
> > 
> > On Mon, Apr 8, 2024, at 7:31 PM, Dmitry Torokhov wrote:
> >> Hi Mark,
> >>
> >> On Sun, Mar 24, 2024 at 05:07:58PM -0400, Mark Pearson wrote:
> >>> Add support for new input events on Lenovo laptops that need exporting to
> >>> user space.
> >>>
> >>> Lenovo trackpoints are adding the ability to generate a doubletap event.
> >>> Add a new keycode to allow this to be used by userspace.
> >>
> >> What is the intended meaning of this keycode? How does it differ from
> >> the driver sending BTN_LEFT press/release twice?
> > 
> > Double tapping on the trackpoint is a unique event - it's not the same as BTN_LEFT twice. The BIOS will send a new ACPI event for it and it's not meant to be the same as mouse button clicks.
> 
> To extend a bit on this, this double-tap event is not reported through
> the PS/2 trackpoint interface at all. Instead it is reported to
> the OS by the ACPI hotkey notifier, which is used to report various
> multi-media hotkeys and things like that, this is handled by
> the thinkpad_apci driver which sofar only reports key-presses.

Ah, I see, so this is just an arbitrary action not connected with the
pointer handling in any way.

For such actions we typically assign keycodes based on their intended
behavior, so instead of KEY_DOUBLECLICK which conveys user gesture but
not the intent you should consider using KEY_CONFIG (with is typically
mapped to Application Launcher - Consumer Control Configuration in HID
spec) or KEY_CONTROLPANEL (Application Launcher - Control Panel).

Thanks.

-- 
Dmitry