LG monitor support

[fiddyschmitt]

Hi Scott,

Do you know if in Windows we can set the I2C source address (to support LG monitors?)

rockowitz/ddcutil#100 (comment)

Thanks,
Fidel

[Prototyped]

To clarify, newer LG monitors cannot switch input source using standard VCP/MCCS commands. Instead they support it as "display dependent devices" (page 14), in this case a proprietary servicing/factory interface. ddcutil v2.0.0-dev branch now supports a hack to be able to send commands with a different I2C source address, and is able to send these display dependent device commands to effect an input source switch on these monitors.

Display dependent devices were things like display-attached keyboards and mice before the widespread advent of USB peripherals that basically disappeared as USB became popular. It is strange that LG chose to use this for their servicing interface.

rockowitz/ddcutil#100 (comment)

Given winddcutil basically uses the win32 Monitor Configuration API (which is strictly limited to DDC/CI), is there scope to be able to send these non-DDC/CI I2C commands to the monitor? (ddcutil is able to do this because Linux exposes an I2C device node for DDC, a much lower-level interface, with which userspace is able to interact directly.)

Looks like with WDDM (the current display driver model introduced with Windows Vista) it is possible to send I/O request packets (IRPs) to the video miniport driver including DDC I2C commands, but it is up to the video miniport driver as to whether it will pass those commands through if they are not DDC/CI commands.

[fiddyschmitt]

Interesting!

[yeahman45]

I have LG monitor and would be very interested porting rockowitz/ddcutil#100 (comment) to winddcutil

[drzony]

NVAPI code for using the side channel: https://gist.github.com/drzony/1744b4f72dcd4fde309a125445c474a1