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

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Message-ID: <569541B4.1020905@kevinlocke.name>
Date:	Tue, 12 Jan 2016 10:11:00 -0800
From:	Kevin Locke <kevin@...inlocke.name>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	ibm-acpi-devel@...ts.sourceforge.net
Cc:	Johannes Stezenbach <js@...21.net>,
	Pali Rohár <pali.rohar@...il.com>,
	linux-kernel@...r.kernel.org, Fabio D'Urso <fabiodurso@...mail.it>,
	platform-driver-x86@...r.kernel.org, Pavel Machek <pavel@....cz>,
	Darren Hart <dvhart@...radead.org>
Subject: Re: [ibm-acpi-devel] [PATCH] thinkpad_acpi: Add support for keyboard
 backlight

On 01/12/2016 08:07 AM, Henrique de Moraes Holschuh wrote:
> On Mon, Jan 11, 2016, at 19:12, Johannes Stezenbach wrote:
>> I can confirm this, my x230 has both.  FWIW, BIOS hotkey
>> Fn+Space cycles through off, dim backlight, full backlight
>> and full thinklight. /sys/class/leds/tpacpi::thinklight/brightness
>> can be read (showing either 0 or 255) but writes are ignored.
>> Dito for /proc/acpi/ibm/light.
>
> We likely need to integrate better (future work) the new backlight
> control with the thinklight control and the firmware interface in the
> x230.
>
> Is the ACPI AML for fn+space readable enough, or is it trapping directly
> into SMM?  Because if it interacts with the traditional higher-level
> ACPI AML we already use to talk to the thinklight (and now to the
> backlight), it should be relatively easy to fix the driver to better
> support the x230.

I looked through the DSDT and SSDT AML on the T430 (which also has both 
a keyboard backlight and ThinkLight) and couldn't deduce which method 
was being invoked for Fn+Space or an analog to MLCG/MLCS for the 
ThinkLight.  However, that may be due to my inexperience interpreting 
AML.  I'll keep looking/learning.

I've posted the files online if anyone else has time/interest to take a 
look:  https://kevinlocke.name/misc/t430-acpi/

Best regards,
Kevin