linux-kernel - Re: [PATCH] leds: rgb: Implement per-key keyboard backlight for several TUXEDO devices

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Message-ID: <ZSe1GYLplZo5fsAe@duo.ucw.cz>
Date:   Thu, 12 Oct 2023 10:58:01 +0200
From:   Pavel Machek <pavel@....cz>
To:     Werner Sembach <wse@...edocomputers.com>
Cc:     Lee Jones <lee@...nel.org>, linux-kernel@...r.kernel.org,
        linux-leds@...r.kernel.org
Subject: Re: [PATCH] leds: rgb: Implement per-key keyboard backlight for
 several TUXEDO devices

Hi!

> From: Christoffer Sandberg <cs@...edo.de>
> 
> Implement per-key keyboard backlight in the leds sysfs interface for
> several TUXEDO devices using the ite8291 controller.
> 
> There are however some known short comings:
> - The sysfs leds interface does only allow to write one key at a time. The
> controller however can only update row wise or the whole keyboard at once
> (whole keyboard update is currently not implemented). This means that even
> when you want to updated a whole row, the whole row is actually updated
> once for each key. So you actually write up to 18x as much as would be
> required.
> - When you want to update the brightness of the whole keyboard you have to
> write 126 sysfs entries, which inherently is somewhat slow, especially when
> using a slider that is live updating the brightness.
> - While the controller manages up to 126 leds, not all are actually
> populated. However the unused are not grouped at the end but also in
> between. To not have dead sysfs entries, this would require manual testing
> for each implemented device to see which leds are used and some kind of
> bitmap in the driver to sort out the unconnected ones.
> - It is not communicated to userspace which led entry controls which key
> exactly

Sooner or later, we'll need to support these keyboards.

But this has way too many shortcomings (and we'd be stuck with the
interface forever).

These days, displays with weird shapes are common. Like rounded
corners and holes in them. Perhaps this should be better modelled as a
weird display?

Best regards,
									Pavel
-- 
People of Russia, stop Putin before his war on Ukraine escalates.

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