ALS + backlight powerd prefs

Introduction

This document describes the interaction between powerd prefs related to ambient light sensors (ALS), backlights (both internal / panel and keyboard), and Ambient EQ.

Keywords

	Description
ALS	Ambient light sensor.
powerd pref	Parameters in powerd that can be set per board or model. File name format is internal_backlight_als_steps in powerd.
Default pref	Part of powerd pref. Default value is in the file.
Optional pref	Part of powerd pref. Default value is in the code.
Panel	Internal display.
Ambient EQ	Color temperature of the internal display.

Powerd pref and chromeos_config

Used in the order listed in Chrome OS Power Management FAQ. If you intend to set a pref to a different value from in powerd, please set in chromeos_config and/or boxster. Links to pref files in powerd are provided as example values.

No ALS

• No need to set has_ambient_light_sensor or set to 0.
• If necessary, set internal_backlight_no_als_ac_brightness, internal_backlight_no_als_battery_brightness.

No keyboard backlight

• No need to set has_keyboard_backlight or set to 0.

With keyboard backlight

• Set has_keyboard_backlight to 1.
• If necessary, set keyboard_backlight_no_als_brightness.
• Doc explaining how keyboard backlight related prefs work.

1 ALS

• Set has_ambient_light_sensor to 1.
• If necessary, set internal_backlight_als_steps (example).
• Doc explaining how internal display backlight related prefs work.

No keyboard backlight

• No need to set has_keyboard_backlight or set to 0.

With keyboard backlight

• Set has_keyboard_backlight to 1.
• If necessary, set keyboard_backlight_als_steps.

2 ALS: 1 for internal display backlight, 1 for keyboard backlight

• In EC, make sure that ALS for internal display backlight has location lid (example) and ALS for keyboard backlight has location base (example).
• Set has_ambient_light_sensor to 2.
• Set has_keyboard_backlight to 1.
• If necessary, set internal_backlight_als_steps and keyboard_backlight_als_steps.

Summary of the above

ALS	KB backlight	has_ambient_light_sensor	has_keyboard_backlight	Consider set other powerd prefs
0	N	0 or not set	0 or not set	internal_backlight_no_als_ac_brightness, internal_backlight_no_als_battery_brightness
0	Y	0 or not set	1	internal_backlight_no_als_ac_brightness, internal_backlight_no_als_battery_brightness, keyboard_backlight_no_als_brightness
1	N	1	0 or not set	internal_backlight_als_steps
1	Y	1	1	internal_backlight_als_steps, keyboard_backlight_als_steps
2	Y	2	1	internal_backlight_als_steps, keyboard_backlight_als_steps

Ambient EQ

Needs official sign off to enable Ambient EQ. Make sure that the color ALS is well tuned, and set the coefficients in EC (example). On top of the settings above, set allow_ambient_eq to 1.