linux-kernel - Re: Implement per-key keyboard backlight as auxdisplay?

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Date: Thu, 18 Jan 2024 23:32:45 +0100
From: Werner Sembach <wse@...edocomputers.com>
To: Pavel Machek <pavel@....cz>
Cc: Hans de Goede <hdegoede@...hat.com>,
 Jani Nikula <jani.nikula@...ux.intel.com>, jikos@...nel.org,
 Jelle van der Waa <jelle@...aa.nl>,
 Miguel Ojeda <miguel.ojeda.sandonis@...il.com>, Lee Jones <lee@...nel.org>,
 linux-kernel@...r.kernel.org,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 linux-input@...r.kernel.org, ojeda@...nel.org, linux-leds@...r.kernel.org
Subject: Re: Implement per-key keyboard backlight as auxdisplay?

Hi

Am 18.01.24 um 18:45 schrieb Pavel Machek:
> Hi!
>
>> We have an upcoming device that has a per-key keyboard backlight, but does
>> the control completely via a wmi/acpi interface. So no usable hidraw here
>> for a potential userspace driver implementation ...
>>
>> So a quick summary for the ideas floating in this thread so far:
>>
>> 1. Expand leds interface allowing arbitrary modes with semi arbitrary
>> optional attributes:
>>      - Con:
>>
>>          - Violates the simplicity paradigm of the leds interface (e.g. with
>> this one leds entry controls possible multiple leds)
> Let's not do this.
>
>> 2. Implement per-key keyboards as auxdisplay
>>
>>      - Pro:
>>
>>          - Already has a concept for led positions
>>
>>          - Is conceptually closer to "multiple leds forming a singular entity"
>>
>>      - Con:
>>
>>          - No preexisting UPower support
>>
>>          - No concept for special hardware lightning modes
>>
>>          - No support for arbitrary led outlines yet (e.g. ISO style enter-key)
> Please do this one.

2 more maybe cons to add to this that popped into my mind just now:

- How would lightbars, or mice fit into this?

- How do 3-zone, 4-zone, n-zone keyboards fit into this? aka how many zones to 
be considered an aux display?

>
>> 3. Implement in input subsystem
>>
>>      - Pro:
>>
>>          - Preexisting concept for keys and key purpose
>>
>>      - Con:
>>
>>          - Not in scope for subsystem
>>
>>          - No other preexisting light infrastructure
> Or negotiate with input people to do this.
>
>> 4. Implement a simple leds driver only supporting a small subset of the
>> capabilities and make it disable-able for a userspace driver to take over
> No. Kernel should abstract this away.
>
> Best regards,
> 									Pavel

Kind regards,

Werner