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

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Message-ID: <20160112163514.GA24900@sig21.net>
Date:	Tue, 12 Jan 2016 17:35:14 +0100
From:	Johannes Stezenbach <js@...21.net>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Pali Rohár <pali.rohar@...il.com>,
	Darren Hart <dvhart@...radead.org>,
	Pavel Machek <pavel@....cz>,
	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 Tue, Jan 12, 2016 at 02:07:10PM -0200, 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 have no clue about ACPI, do you have some hints
how to get the info you want?  I found this:

  sudo acpidump > acpidata.dat
  acpixtract -sSSDT acpidata.dat
  acpixtract -sDSDT acpidata.dat
  iasl -d DSDT.dat SSDT*.dat

  ..and then look at the .dsl files that contain the AML assembler. 

But what to look out for?

PS: failed to mention my x230 kernel was still 4.2.x in case it matters

Thanks,
Johannes