Diagnosing HP 22cwa Invalid display and DDC communication failed about ddcutil HOT 4 CLOSED

The combination of ryzen integrated video and your particular monitor is resulting in invalid DDC/CI reply packets. You are correct that that's what the output from --ddc is showing. The repeated DDCRC_DDC_DATA status codes on ddcutil detect also indicate the same thing. Beyond setting a high sleep multiplier the only ddcutil option that has a remote possibility of correcting this is --use-file-io which causes ddcutil to take an alternative path through driver i2c_dev.

Of course, connecting a different display to the laptop and trying the monitor on another computer might isolate the problem to the monitor.

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I don't think I have another monitor that supports DDC, so might be a while before I can get around to testing that.

My other older computer uses Intel 620 integrated graphics and I did test it on there as well and still have a similar issue (I should note that that one is connecting using a Thunderbolt hub; not direct HDMI).

Here are those files:

sudo-ddcutil-detect---ddc.intel.txt
sudo-ddcutil-detect---verbose.intel.txt
.intel.txt)
sudo-ddcutil-interrogate---verbose.intel.txt

Notably the byte shift seems to happen there too. I tested with various --sleep-multiplier values (2 4 10 15 20 99) and it still fails.

Using --use-file-io also fails similarly on both computers.

Also of note, I got "DDC: Quirk: response packet starts with double 0x6e" a few times (it is very inconsistent but saw it on the ryzen computer when while using the --use-file-io option.

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Given that the data errors persist when you move the monitor to another computer strongly suggests the problem is in the monitor's DDC implementation.

The initial double 0x6e is one of the few situations where ddcutil can recover from invalid data.

As a practical matter, there's no point in trying a sleep multiplier greater than 4.

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Ok, sounds good. Thanks for the help. Is there anything else that needs to be done--like adding this to the docs? (I don't know if it is important given this monitor seems to be practically forgotten by everyone except HP.) If not, I'll mark this issue as resolved.

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