how to set brightness on a hdmi display

[edward_fu]

Hello,

There is a case of setting brightness on a hdmi display with imx8mq board.

The hdmi display can support adjusting brightness by DDC/CI protocol, which already implemented in windows application.

So how can I do in imx8mq to set brightness by DDC(HDMI_DDC_SDA, HDMI_DDC_SCL).

Thanks very much.

[tomsong]

Hi,

     I tried the attached recipe for ddcutil and it can detect the display however I got a "DDC communication failed" error:

    root@imx8mp-var-dart:~# ddcutil detect
    Invalid display
    I2C bus: /dev/i2c-6 
    EDID synopsis:
    Mfg id: MST
    Model: MStar Demo
    Product code: 48
    Serial number:
    Binary serial number: 1 (0x00000001)
    Manufacture year: 2010, Week: 10
    DDC communication failed

    Any suggestions of how to fix it?

    Thanks a lot!

    Regards,

    Tom 
  

[belpai]

Have you found a way to do that correctly with the imx8mq? @edward_fu @tomsong 

[Zhiming_Liu]

Hi

Please see this https://blog.tcharles.fr/ddc-ci-screen-control-on-linux/

BR

Zhiming

[edward_fu]

Hi Zhiming,

Thanks for your quick reply.

The solution is general , but is suitable for imx8mq? Because the ddcutil tool you mentioned need i2c-dev module to be loaded. As we know imx8mq DDC uses HDMI_DDC_SDA, HDMI_DDC_SCL not a common i2c.

Thanks again.

Br,

Edward

[Zhiming_Liu]

Add this folder into /imx-yocto-bsp/sources/meta-imx/meta-bsp/recipes-support/

And bitbake ddcutil

[Zhiming_Liu]

Hi

I am finding perfect solution to send ddc message and will update later.

The ddcutil can used in i.mx8mq,i am trying to use i2ctools 

BR

Zhiming

[edward_fu]

Hi

Thanks for your support. One question, the solution you suggested is still using ddcutil, just compling with yocto. Is it the same with apt-get install ddcutil? 

Another question, the .bb fiel you provided indicated that dduutil tool depends on x11(xserver). But as I know imx8mq only supports wayland.

Br

Edward