DELL U4924DW - videoswap/usbswitch

[nobanzai]

For a few days now I am using a DELL U4924DW monitor with usb-c, kvm and pip/pbp capabilities.
I found out, that feature 0xe5 can be used for swapping video, 0xe7 for switching usb.
Quering these features, returns:

• DISPLAY=1
• ddcutil --display 1 getvcp 0xe5
  VCP code 0xe5 (Manufacturer Specific ): mh=0x00, ml=0x02, sh=0x00, sl=0x01
• ddcutil --display 1 getvcp 0xe7
  VCP code 0xe7 (Manufacturer Specific ): mh=0xff, ml=0xff, sh=0x15, sl=0x00

I then tried to switch video and usb with

• DISPLAY=1
• ddcutil --display 1 setvcp 0xe5 0xf000
  Setting value failed for feature e5, rc=DDCRC_NULL_RESPONSE(-3002): received DDC null response
• ddcutil --display 1 setvcp 0xe7 0xff00
  Setting value failed for feature e7, rc=DDCRC_ALL_RESPONSES_NULL(-3011): all tries returned DDC Null Message

Both video and usb are swapped as desired, but I also get the above shown messages.
Afterwards the OSD can't be activated until the monitor is switched off and back on.

What am I doing wrong here?

ddcutil-1.4.1-2.2.x86_64 on openSUSE Tumbleweed 20230712

TIA.
Bye.
Michael.

[rockowitz]

1. Try using --noverify on the setvcp command. Features xE5 and xE7 may be write-only. As they are manufacturer-specific features and not in the MCCS spec, ddcutil has no way of knowing that they are write-only.

2. If your monitor supports feature xCA (OSD/Button Control) it may be possible to re-enable the OSD using that feature. See ddcutil vcpinfo ca --verbose for values. (If the VCP version of your monitor is 2.2, the high order byte (SH) of the value is used for extended button control. See the MCCS spec for details.)

[nobanzai]

Thx for your answer. With --noverify return value is 0 and I don't get an error message.
Regarding ddcutil vcpinfo ca --verbose:

VCP code CA: OSD/Button Control
Sets and indicates the current operational state of OSD (and buttons in v2.2)
MCCS versions: 2.0, 2.1, 3.0, 2.2
MCCS specification groups: Control, Miscellaneous
ddcutil feature subsets:
Attributes (v2.0): Read Write, Non-Continuous (simple)
Attributes (v2.1): Read Write, Non-Continuous (simple)
Attributes (v3.0): Read Write, Non-Continuous (simple)
Attributes (v2.2): Read Write, Non-Continuous (complex)
Simple NC values:
0x01: OSD Disabled
0x02: OSD Enabled
0xff: Display cannot supply this information
Simple NC values:
0x01: OSD Disabled
0x02: OSD Enabled
0xff: Display cannot supply this information

So what would be the correct command to reenable osd?

TIA.
Bye.
Michael

[rockowitz]

ddcutil setvcp ca 2

[nobanzai]

Doesn't help - osd still can't be activated after setting 0xe5/0xe7.
Besides that "ddcutil getvcp 0xca" already returns 0x02, so osd should be active.

[nobanzai]

0xe7 is working without problems, only 0xe5 leads to the osd problem.
Besides that, 0xe5 seems to destabilize the ucb-c connection. A few times the monitor lost the connection to the notebook connected via usb-c.

[nobanzai]

It seems to be a timing problem - if I wait for 2 seconds between the two setvcp commands, everything is ok: OSD menu can be activated and no usb-c problems so far.

[nobanzai]

Works for me.