Difference between revisions of "How to modify the panel backlight"

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Template:ArticleMainWriter Template:ReviewersList Template:ArticleProposedVersion Template:ArticleToBeReviewedByTW ArticleApprovedVersion


First of all, you need to identify the backlight device linked to your panel, thanks to the sysfs: 

 ls /sys/class/backlight
5a000000.dsi.0

In the above example, there is a single entry named "5a000000.dsi.0", which is replaced by "*" in the below command.


To adjust the panel backlight, enter the following command: 

 echo 32 > /sys/class/backlight/*/brightness    # set the dsi panel backlight to the value 32

Note: Be sure to use Only values between 0 and max_brightness must be used.

To get the maximum panel backlight value, enter: 

 cat /sys/class/backlight/*/max_brightness
255

To get the actual panel backlight value, enter: 

 cat /sys/class/backlight/*/actual_brightness
32


Use one of the next following commands for to quickly test the panel backlight: 

 export bl=/sys/class/backlight/5a000000.dsi.0/brightness

 # switch on/off test
 (while true; do echo 0 > $bl; sleep 0.5; echo 255 > $bl; sleep 0.5; done)

 # slow 32-step tests
 (i=0; while true; do i=$(((i+32)%256)); echo $i > $bl; sleep 0.5; done)

 # fast 1-step test
 (i=0; while true; do i=$(((i+1)%256)); echo $i > $bl; done)

<noinclude>

{{ArticleMainWriter | PhilippeC }}
{{ReviewersList | YannickF}}
{{ArticleProposedVersionArticleApprovedVersion | PhilippeC | YannickF (Passed, 5feb'19)| No previous approved version | Nobody | 2FebAnneJ - 18Feb'19}}
{{ArticleToBeReviewedByTW | 10715 | 08Feb - 10715 | 18Feb'19}}
[[Category:How to run use cases]]
[[Category:DRM KMS]]</noinclude>


First of all, you need to identify the backlight device linked to your panel, thanks to the sysfs:
 {{Board$}} ls /sys/class/backlight
 5a000000.dsi.0

In the above example, there is a single entry named "5a000000.dsi.0", which is '''replaced by "*"''' in the below command.

To adjust the panel backlight, enter the following command:
 {{Board$}} echo '''32''' > /sys/class/backlight/*/'''brightness'''    # set the dsi panel backlight to the value '''32'''
Note: Be sure to use Only values between 0 and '''max_brightness''' 
must be used.
To get the maximum panel backlight value, enter:
 {{Board$}} cat /sys/class/backlight/*/'''max_brightness'''
 255

To get the actual panel backlight value, enter:
 {{Board$}} cat /sys/class/backlight/*/'''actual_brightness'''
 32

Use one of the nextfollowing commands forto quickly test the panel backlight:
 {{Board$}} export bl=/sys/class/backlight/5a000000.dsi.0/brightness

 {{Board$}} # switch on/off test
 {{Board$}} (while true; do echo 0 > $bl; sleep 0.5; echo 255 > $bl; sleep 0.5; done)

 {{Board$}} # slow 32-step tests
 {{Board$}} (i=0; while true; do i=$(((i+32)%256)); echo $i > $bl; sleep 0.5; done)

 {{Board$}} # fast 1-step test
 {{Board$}} (i=0; while true; do i=$(((i+1)%256)); echo $i > $bl; done)
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{{ArticleMainWriter | PhilippeC }}
  
{{ArticleMainWriter | PhilippeC }}
 
{{ReviewersList | YannickF}}
  
{{ReviewersList | YannickF}}
−
{{ArticleProposedVersion | PhilippeC | YannickF (Passed, 5feb'19)| No previous approved version | Nobody | 2Feb'19}}
+
{{ArticleApprovedVersion | PhilippeC | YannickF (Passed, 5feb'19)| No previous approved version | AnneJ - 18Feb'19 - 10715 | 18Feb'19}}
−
{{ArticleToBeReviewedByTW | 10715 | 08Feb'19}}
  
 
[[Category:How to run use cases]]
  
[[Category:How to run use cases]]
 
[[Category:DRM KMS]]
  
[[Category:DRM KMS]]
 
</noinclude>
  
</noinclude>
   
−
First of all, you need to identify the backlight device linked to your panel thanks to the sysfs:
 +
First identify the backlight device linked to your panel, thanks to the sysfs:
 
  {{Board$}} ls /sys/class/backlight
  
  {{Board$}} ls /sys/class/backlight
 
  5a000000.dsi.0
  
  5a000000.dsi.0
   
−
In the above example, there is a single entry named "5a000000.dsi.0", '''replaced by "*"''' in the below command.
 +
In the above example, there is a single entry named "5a000000.dsi.0", which is '''replaced by "*"''' in the below command.
   
   
−
To adjust the panel backlight, enter:
 +
To adjust the panel backlight, enter the following command:
 
  {{Board$}} echo '''32''' > /sys/class/backlight/*/'''brightness'''    # set the dsi panel backlight to the value '''32'''
  
  {{Board$}} echo '''32''' > /sys/class/backlight/*/'''brightness'''    # set the dsi panel backlight to the value '''32'''
−
Note: Be sure to use values between 0 and '''max_brightness'''
 +
Note: Only values between 0 and '''max_brightness''' must be used.
   
 
To get the maximum panel backlight value, enter:
  
To get the maximum panel backlight value, enter:
Line 28: Line 27:
   
   
−
Use one of the next commands for quickly test the panel backlight:
 +
Use one of the following commands to quickly test the panel backlight:
 
  {{Board$}} export bl=/sys/class/backlight/5a000000.dsi.0/brightness
  
  {{Board$}} export bl=/sys/class/backlight/5a000000.dsi.0/brightness
 
   
  
   
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