About How to verify and enbale backlight driver

Can you let me know the following information:

  1. How to enable backlight(based on PWM) driver in TX2?
  2. I believe that the related dts file need to update,right? if so, what’s the detail dts file?


Each backlight driver is implemented/enabled in the panel driver itself. Please download the kernel source and check the “panel” folder under dc.

Hi WayneWWW,

Thanks you very much for your quickly replay.

But In your L4T_R28.2_Documentation on Configuring Pulse Width Modulation say:

Backlight control to the panel is done through Pulse Width Modulation (PWM) or Parametric Four-Wave Mixing (PWFM) or through the backlight device embedded in the panel.
The PFW and PFWM driver located at:
The driver file for the backlight device embedded in the panel is:
For example, the backlight for the LG 5 inch 720p panel on pluto is driven by the embedded max8831 integrated circuit (IC). That driver file is:
To make backlight increment in a linear manner to the brightness increment, backlight is calibrated and the corresponding values are stored in the backlight response curve.

Also, Can you also let me know how to access backlight(based on PWM) driver by user application?

Sorry for my previous comment, the backlight driver we are using by default is the lp855.c.
You could refer to the device tree and search the node “lp8557-backlight-s-wuxga-8-0@2c”.


Sure, I will check it tomorrow.
Also, I just started to contact Linux development. Can you response my priary question as following:
What's the general way to control backlight brightness by user app?
Are there one sameple for my reference?


You could use the sysfs under backlight node to control the it (maximum value is 255).