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

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Date: Mon, 08 Apr 2024 20:00:30 -0400
From: "Mark Pearson" <mpearson-lenovo@...ebb.ca>
To: "Dmitry Torokhov" <dmitry.torokhov@...il.com>
Cc: "Hans de Goede" <hdegoede@...hat.com>,
 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

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.

For example, on Windows this launches a utility that let's you do various configurations on your laptop (some Lenovo specific), but that's not available on Linux (yet). We did want to make it flexible in this implementation so users could use it for whatever was useful to them.

>> 
>> Lenovo support is using FN+N with Windows to collect needed details for
>> support cases. Add a keycode so that we'll be able to provide similar
>> support on Linux.
>
> Is there a userspace consumer for this?

There isn't yet, though we would like to implement something, and do plan to. 
We still have to work through the details of the best way to do this, and if it's Lenovo specific, or (probably better) something generic.

I don't have as much knowledge on the user-space side development, and my experience is it tends to move a bit slower for getting things implemented. We thought we'd get the framework in, so it's available, and then work with user-space folk to deliver a solution in a suitable manner.
Ultimately this is something we'll need in our Linux preloads and the aim is to make it easier for Linux users to get help from our support team (not always the easiest currently).
I don't know if other vendors have something similar, but I wouldn't be surprised if this could be re-used in other cases so I hope it's not Lenovo specific. It felt like it would be useful functionality to have :)

Mark