I got a new monitor (DELL U3821DW) and am using a tool to switch input sources from the command line. My 2 old Dell monitors always worked fine with this tool and returned the standard value 0x0F when using the DisplayPort and 0x11 when using the HDMI 1 input port. 

The U3821DW returns however for VCP Code 60 (Input Select) the value 3855 (0xF0F) when using DisplayPort 1. And when using the Input source HDMI 1 the value used is displayed as 4369 (0x1111).

I only changed the monitor, all other components: video-card, OS, etc. are the same.

 

The specifications (VESA Monitor Control Command Set Standard Version 2.2a) shows that VCP Code 60 is a single byte value and the other 3 bytes should always be set to 0.

 

Is this a known issue of this monitor type or has the second byte a special meaning?