BackLight
From ArmadeusWiki
This page will explain you how to configure and use the Linux driver controlling the BackLight of your LCD
Contents
[hide]Introduction
Backlight control is done through the i.MXL/i.MX27 integrated backlight PWM (inside LCDC module). The output signal of this PWM is redirected to the BACKLIGHT pin of your LCD connector.
In short the driver is mainly exporting a /sys interface to user space, allowing you to change the Duty Cycle of the PWM output signal and so the backlight intensity of the LCD.
Installation
$ make linux26-menuconfig
- in Device Drivers ---> Graphics support ---> Backlight & LCD device support, select <M> Lowlevel Backlight controls
- in Device Drivers ---> Armadeus specific drivers ---> Support for specific Armadeus drivers, select <M> i.MXL backLight driver
- If built in kernel, reflash your kernel image; if selected as module either reflash your rootfs or copy backlight.ko, imx_bl.ko and .../lib/modules/2.6.18.1/modules.dep to your target (for more infos: Linux_drivers_generalities). Then on your APF:
# modprobe imx_bl i.MX Backlight driver v0.X initialized.
Usage
All backlight controls are done through the /sys interface:
# ls /sys/class/backlight/imxl-bl/ actual_brightness max_brightness subsystem brightness power uevent
- To see the actual brightness:
# cat /sys/class/backlight/imxl-bl/actual_brightness
- To see the max allowed brightness:
# cat /sys/class/backlight/imxl-bl/max_brightness
- To change the brightness:
# echo 100 > /sys/class/backlight/imxl-bl/brightness
There is a small test script in target/linux/modules/backlight/test/
