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

From: Kevin Locke
Date: Tue Jan 12 2016 - 13:17:52 EST

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

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:

Best regards,