Switching Input on LG Monitors

[rockowitz]

This page is a continuation of the extensive discussion on issue #100, LG29UM69G fails switching input.

[hartman]

I've made a start with the page. Hopefully others can add and improve.

[rockowitz]

Nice summary!!

[theli-ua]

how is GP850 explicitly not supported and potentially supported?

[hartman]

Good question, but considering these values were reverse engineered from the firmware, its really hard to say. Either the firmware was misinterpreted, or the manufacturer just made mistakes.

[theli-ua]

Also, what branch do we need to build to try those? 2.0.0-rc1 seem to not support the i2c source addr option

[rockowitz]

2.0.0-dev

[inkhey]

Hello, I did try switching monitor on LG 34UM88C-P on Pop!_OS 22.04 LTS and unlike other LG display it seems to work pretty well without the last version. I wanted to share this information.

I did try this on both PBP and standard mode.

❯ ddcutil --version
ddcutil 1.2.2

Display 1
   I2C bus:  /dev/i2c-11
   EDID synopsis:
      Mfg id:               GSM
      Model:                LG ULTRAWIDE
      Product code:         23266
      Serial number:        
      Binary serial number: [REDACTED]
      Manufacture year:     2018,  Week: 3
   VCP version:         2.1

❯ ddcutil capabilities --display 1 --verbose
...
   Feature: 60 (Input Source)
      Values (unparsed):  11 12 0F 10
      Values (  parsed):
         11: HDMI-1
         12: HDMI-2
         0f: DisplayPort-1
         10: DisplayPort-2

In fact the correct value are:

• 00 -> DisplayPort
• 01 -> HDMI 1
• 10 -> HDMI 2

❯ ddcutil --display 1 getvcp 60
VCP code 0x60 (Input Source                  ): Invalid value (sl=0x00)

The value is incorrect, but the switch does work as expected:

❯ ddcutil setvcp 60 0x10

[5685C4A059D5]

Reporting my findings on my 27UL600:

• It responds to DDC 0x60, but switching to/between HDMI inputs is buggy (might be because internally there's only one HDMI input). The OSD also doesn't reflect the input change.
• Does not respond to DDC2AB 0xF4 at all. Not even a blink.
• Responds to 0xD7 over both DDC and DDC2AB. PBP works even though I don't think the monitor is supposed to have this feature.

[jrowny]

For 38WR85QC-W

Works with 0xF4 on the 0x50 address:

x00D0 = Display Port
x00D1 = USB-C

I think 0x0090 and 91 are HDMI1/2 as they respond, but I don't have anything hooked up there.