linux-kernel - Re: [PATCH] thinkpad_acpi: Add support for keyboard backlight

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Date:	Wed, 13 Jan 2016 09:54:55 +0100
From:	Pali Rohár <pali.rohar@...il.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Darren Hart <dvhart@...radead.org>,
	ibm-acpi-devel@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	Fabio D'Urso <fabiodurso@...mail.it>
Subject: Re: [PATCH] thinkpad_acpi: Add support for keyboard backlight

On Tuesday 12 January 2016 22:58:04 Pavel Machek wrote:
> Hi!
> 
> On Mon 2016-01-11 21:03:01, Pali Rohár wrote:
> > On Monday 11 January 2016 20:28:00 Henrique de Moraes Holschuh wrote
> > > The two features are not the same (and are handled differently by the
> > > firmware, for whatever reason), although they do serve the same
> > > purpose. I don't think a thinkpad will ever have both features at
> > > the same time, so I have no idea why they changed the firmware
> > > interface.
> > 
> > Maybe we should decide if ::kbd_backlight LED suffix could be used also 
> > for other LED devices and not only for those which are physically under 
> > the keyboard.
> 
> Another problem is that N900 has _6_ backlight LEDs. Named
> lp5523::kb1..6. ... Which does means desktop software will probably
> not pick them up :-(. 
> 
> I guess we could have "/sys/class/kbd_light/brightness" that would
> control all of them with one write.

Probably... But there is problem that lp5523 is not ordinary on/off
light, it can be programmed to execute own "light" application.

> Next question is.. apparently there are some keyboards that have
> per-key RGB backlight... but maybe we can just call that "weird
> enough" and ignore...

First we need to defines stable kernel ABI for keyboard backlight. And I
suggest to use existing convention used by upower/console-kit and other
userspace apps...

-- 
Pali Rohár
pali.rohar@...il.com