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

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Message-ID: <ZarcZwQd/2EXjgZP@duo.ucw.cz>
Date: Fri, 19 Jan 2024 21:32:39 +0100
From: Pavel Machek <pavel@....cz>
To: Werner Sembach <wse@...edocomputers.com>
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!

> > > And then storing RGB in separate bytes, so userspace will then
> > > always send a buffer of 192 bytes per line (64x3) x 14 rows
> > > = 3072 bytes. With the kernel driver ignoring parts of
> > > the buffer where there are no actual keys.
> > That's really really weird interface. If you are doing RGB888 64x14,
> > lets make it a ... display? :-).
> > 
> > ioctl always sending 3072 bytes is really a hack.
> > 
> > Small displays exist and are quite common, surely we'd handle this as
> > a display:
> > https://pajenicko.cz/displeje/graficky-oled-displej-0-66-64x48-i2c-bily-wemos-d1-mini
> > It is 64x48.
> > 
> > And then there's this:
> > https://pajenicko.cz/displeje/maticovy-8x8-led-displej-s-radicem-max7219
> > and this:
> > https://pajenicko.cz/displeje/maticovy-8x32-led-displej-s-radicem-max7219
> > 
> > One of them is 8x8.
> > 
> > Surely those should be displays, too?
> 
> But what about a light bar with, lets say, 3 zones. Is that a 3x1 display?
> 
> And what about a mouse having lit mousebuttons and a single led light bar at
> the wrist: a 2x2 display, but one is thin but long and one is not used?

So indeed LEDs can arranged into various shapes. Like a ring, or this:

 * *
* * *
 * *

https://pajenicko.cz/led-moduly?page=2

Dunno. Sounds like a display is still a best match for them. Some of
modules are RGB, some are single-color only, I'm sure there will be
various bit depths.

I guess we can do 3x1 and 2x2 displays. Or we could try to solve
keyboards and ignore those for now.

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

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