# Display Data Channel DDCUtil stopped detecting both monitors after 470.57.02 update

**URL:** <https://forums.developer.nvidia.com/t/display-data-channel-ddcutil-stopped-detecting-both-monitors-after-470-57-02-update/184262>\
**Category:** Linux\
**Created:** [July 21, 2021, 5:35am UTC](https://forums.developer.nvidia.com/t/display-data-channel-ddcutil-stopped-detecting-both-monitors-after-470-57-02-update/184262 "2021-07-21T05:35:44Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![michaelkhi8y](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/michaelkhi8y/32/281587_2.png) [@michaelkhi8y](https://forums.developer.nvidia.com/u/michaelkhi8y)\
**Post date:** [July 21, 2021, 5:35am UTC](https://forums.developer.nvidia.com/t/display-data-channel-ddcutil-stopped-detecting-both-monitors-after-470-57-02-update/184262/1 "2021-07-21T05:35:44Z")

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I just updated to 470.57.02 from the OpenSUSE Tumbleweed repo. Prior to the update (and reboot) I was successfully using ddcutil to change the brightness of my two monitors, but now ddcutil detect only reports one of them:

```auto
% ddcutil detect  
Display 1
   I2C bus: /dev/i2c-8
   EDID synopsis:
      Mfg id: GSM
      Model: LG HDR 4K
      Serial number:    
      Manufacture year: 2019
      EDID version: 1.4
   VCP version: 2.1

```

Ddutil used to display two monitors, “DDC-Display” 1 used to be an HP ZR24w (DVI-\>HDMI cable connected), and DDC-Display 2 was my LG HDR 4K (displayport cable), but now ddutil only reports my LG display as DDC-Display 1. The only change was an update to the nvidia driver and a reboot (twice to check the problem would shake loose). In other respects the two monitors are working normally.

Is this a known issue for 470.57.02?

---

<div class="post-metadata">

**Author:** ![michaelkhi8y](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/michaelkhi8y/32/281587_2.png) [@michaelkhi8y](https://forums.developer.nvidia.com/u/michaelkhi8y)\
**Post date:** [July 21, 2021, 6:18am UTC](https://forums.developer.nvidia.com/t/display-data-channel-ddcutil-stopped-detecting-both-monitors-after-470-57-02-update/184262/2 "2021-07-21T06:18:40Z")

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I found some old notes I had made, they had not been applied to this system:

```auto
- Nvidia enable i2c
    - Needed for ddcutil - not really of any use at this point, but included for reference
    - xorg.conf
        Section "Device"
            Identifier "Device0"
            Driver "nvidia"
            Option "RegistryDwords" "RMUseSwI2c=0x01; RMI2cSpeed=100"
            VendorName "NVIDIA Corporation"
            BoardName "GeForce GTX 1650 SUPER"
        EndSection
    - /etc/modprobe.d/99-local.conf and run ldconfig afterwards:
        options nvidia NVreg_RegistryDwords=RMUseSwI2c=0x01;RMI2cSpeed=100

```

I applied them and now ddcutil reports both monitors:

```auto
ddcutil detect  ✔  10001  18:11:42
Display 1
   I2C bus: /dev/i2c-5
   EDID synopsis:
      Mfg id: HWP
      Model: HP ZR24w
      Serial number: XXXXXXXXX
      Manufacture year: 2010
      EDID version: 1.3
   VCP version: 2.2

Display 2
   I2C bus: /dev/i2c-8
   EDID synopsis:
      Mfg id: GSM
      Model: LG HDR 4K
      Serial number:    
      Manufacture year: 2019
      EDID version: 1.4
   VCP version: 2.1

```

For some reason, prior to kernel 5.13.2-1-default, nvidia and ddcutil was working without these config entries.

I actually rebooted to 5.13.1-1 to check and yes ddutil works without these settings (although the boot with the new 470 driver does actually make it to sddm).

Everything’s back to what it should be now.

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<div class="post-metadata">

**Author:** ![system](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/system/32/68080_2.png) [@system](https://forums.developer.nvidia.com/u/system)\
**Post date:** [September 19, 2021, 6:19am UTC](https://forums.developer.nvidia.com/t/display-data-channel-ddcutil-stopped-detecting-both-monitors-after-470-57-02-update/184262/3 "2021-09-19T06:19:01Z")

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