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

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Date: Thu, 11 Apr 2024 14:30:35 +0200
From: Hans de Goede <hdegoede@...hat.com>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>,
 Mark Pearson <mpearson-lenovo@...ebb.ca>
Cc: Peter Hutterer <peter.hutterer@...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>
Subject: Re: [PATCH 1/4] Input: Add trackpoint doubletap and system debug info
 keycodes

Hi Dmitry,

On 4/11/24 2:02 AM, Dmitry Torokhov wrote:
> On Tue, Apr 09, 2024 at 10:17:05PM -0400, Mark Pearson wrote:
>> Hi Dmitry
>>
>> On Tue, Apr 9, 2024, at 9:20 PM, Dmitry Torokhov wrote:
>>> On Tue, Apr 09, 2024 at 02:47:05PM -0700, Dmitry Torokhov wrote:
>>>> On Tue, Apr 09, 2024 at 03:23:52PM +1000, Peter Hutterer wrote:
>>>>> On 09/04/2024 09:31, 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?
>>>>>>>
>>>>>>> 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?
>>>>>
>>>>> Funnily enough XKB has had a keysym for this for decades but it's not
>>>>> hooked up anywhere due to the way it's pointer keys accessibility
>>>>> feature was implemented. Theory is that most of userspace just needs
>>>>> to patch the various pieces together for the new evdev code + keysym,
>>>>> it's not really any different to handling a volume key (except this
>>>>> one needs to be assignable).
>>>>
>>>> What is the keysym? If we can make them relatable to each other that
>>>> would be good. Or maybe we could find a matching usage from HID usage
>>>> tables...
>>>
>>> I was looking through the existing codes and I see:
>>>
>>> #define KEY_INFO		0x166	/* AL OEM Features/Tips/Tutorial */
>>>
>>> We also have KEY_VENDOR used in a few drivers/plafrom/x86, including
>>> thinkkpad_acpi.c and I wonder if it would be suitable for this vendor
>>> specific debug info collection application (which I honestly doubt will
>>> materialize).
>>>
>>
>> That's a somewhat disappointing note on your doubts, is that based on
>> anything? Just wondering what we've done to deserve that criticism.
> 
> Sorry, this was not meant as a criticism really, but you mentioned
> yourself that there isn't anything in the works yet, you just have some
> plans.
> 
> For such a project to succeed Lenovo needs to invest into selling
> devices with Linux as a primary operating system, and it has to be
> consumer segment (or small business, because for corporate they
> typically roll their own support channels). The case of retrofitting
> Linux onto a that device originally came with Windows OS rarely gets
> much if any response from the normal support channels.
> 
> Is this something that is actually happening?

Yes, Lenovo is actually offering Fedora as an OS choice when
ordering ThinkPads directly from their website in many countries
including when ordering as a consumer.

And unlike other vendor's Linux preloads which often use a kernel
with downstream laptop specific changes these laptops are running
unmodified Fedora kernels, which themselves are almost pristine
upstream kernels.

Lenovo (Mark) has been really good the last couple of years in
making sure that their hw just works with mainline kernels without
any downstream vendor specific patches.

>> That aside, I guess KEY_INFO or KEY_VENDOR could be a good fit (I
>> personally don't think KEY_CONFIG matches well), but I would be
>> worried about clashing with existing functionality.

Using KEY_INFO / KEY_VENDOR works for me too. So maybe we should
just go with one of those 2 ?

Regards,

Hans