Difference between revisions of "BackLight"

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m (Introduction)
m (Installation)
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  $ make linux26-menuconfig
 
  $ make linux26-menuconfig
 
* in '''Device Drivers ---> Graphics support  ---> Backlight & LCD device support''', select '''<M>  Lowlevel Backlight controls'''  
 
* 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'''  
+
* in '''Device Drivers ---> Armadeus specific drivers ---> Support for specific Armadeus drivers''', select '''<M> i.MX 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:
 
* 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
 
  # modprobe imx_bl

Revision as of 17:55, 19 December 2008

This page will explain you how to configure and use the Linux driver controlling the BackLight of your LCD

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.MX 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/

Links