Bug 489020 - KWin changes monitors' internal DDC VCP values on bootup
Summary: KWin changes monitors' internal DDC VCP values on bootup
Status: RESOLVED WORKSFORME
Alias: None
Product: Powerdevil
Classification: Plasma
Component: general (show other bugs)
Version: 6.1.0
Platform: Other Linux
: NOR normal
Target Milestone: ---
Assignee: Plasma Bugs List
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2024-06-23 05:34 UTC by mr.yamamoto
Modified: 2024-08-29 03:47 UTC (History)
5 users (show)

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Description mr.yamamoto 2024-06-23 05:34:36 UTC
SUMMARY
With my wacom cintiq 16 inch, every time I log into kde it changes the wacoms edid settings. The only way to fix it to factory defaults are to use ddcutil. I see no settings to make this *not* happen. 

STEPS TO REPRODUCE
1. Turn on pc with wacom cintiq 16 inch installed

OBSERVED RESULT
Inaccurate de-saturated colors and incorrect brightness settings. 

EXPECTED RESULT


SOFTWARE/OS VERSIONS

KDE Plasma 6.1 Endavour OS
Comment 1 Nate Graham 2024-06-25 22:01:24 UTC
Is this on X11 or Wayland?

When you say is  changes EDID profile, can you clarify what you mean exactly? Like, the monitor actually shows a different EDID value when yo log into a Plasma session?
Comment 2 mr.yamamoto 2024-06-26 05:26:31 UTC
(In reply to Nate Graham from comment #1)
> Is this on X11 or Wayland?
> 
> When you say is  changes EDID profile, can you clarify what you mean
> exactly? Like, the monitor actually shows a different EDID value when yo log
> into a Plasma session?

This is on wayland. I will check X11 shortly. 

Also sorry, my terminology is incorrect. The thing that are changing are the monitors internal vcp values? IE if you use ddcutil, and get the vcp codes for the monitor, those values change sometimes. Sometimes they don't. There is also no way to change them back to be correct for me except to either use ddcutil, or log into windows and change the value with wacoms driver utility. This behavior was not observed before an upgrade to 6.1
Comment 3 Zamundaaa 2024-06-26 14:59:48 UTC
KWin doesn't touch any monitor settings. The only way this could possibly happen is through powerdevil's ddcutil use for setting the brightness, or some other tool running on your system.
Comment 4 mr.yamamoto 2024-06-27 05:35:50 UTC
(In reply to Zamundaaa from comment #3)
> KWin doesn't touch any monitor settings. The only way this could possibly
> happen is through powerdevil's ddcutil use for setting the brightness, or
> some other tool running on your system.

I don't know how to directly interact with this, but as an example on the desktop there is a brightness and color button on my icon task list. Clicking it, it will let me change the brightness of my primary monitor (only that one) and doing so, in fact, reverts the monitor in question to the incorrect profile. I can then change it back using ddcutil, but before doing that have no other tools to mess with monitor color installed or running. 

Another way to make this happen is if I turn on "auto dim screen after xxx minutes." in power settings. If this is procced, it also messes with the same thing causing the same issue to happen. So whatever you are talking about might be correct, but how do I see what it's actually changing or setting to keep make the incorrect internal profile?
Comment 5 mr.yamamoto 2024-06-27 05:46:05 UTC
To be clear, it seems as though whatever controls the values from kdes side (which it would seem is powerdevil ddcutil?) is changing the values to something that isn't correct, as it's not simply alternating the brightness. What I'm doing to "fix" it, is using ddcutil, and factory resetting the monitor, then changing the brightness to 100. The incorrect thing that is happening, is it doesn't seem to be changing the brightness, but the contrast and other random settings, which was not a behavior I observed until upgrading to 6.1
Comment 6 Jakob Petsovits 2024-07-30 13:09:44 UTC
(In reply to mr.yamamoto from comment #5)
> To be clear, it seems as though whatever controls the values from kdes side
> (which it would seem is powerdevil ddcutil?) is changing the values to
> something that isn't correct, as it's not simply alternating the brightness.
> What I'm doing to "fix" it, is using ddcutil, and factory resetting the
> monitor, then changing the brightness to 100. The incorrect thing that is
> happening, is it doesn't seem to be changing the brightness, but the
> contrast and other random settings, which was not a behavior I observed
> until upgrading to 6.1

What PowerDevil does is to query the monitor's capabilities using libddcutil, and if the "brightness" capability (VCP code 10) is supported then it sets the value for VCP code 10 that to whatever brightness is requested by other Plasma components. The main components that request brightness changes are the Brightness and Color applet as well as the "Dim screen" option in System Settings / Power Management. Plasma 6.1 does not set brightness on session start-up.

The part that's new in Plasma 6.1 is that we're now also observing monitor connection & disconnection & sleep events through a function that was introduced recently in libddcutil 2.x. There is a chance that somehow your Wacom responds poorly to this? But I don't know what DDC commands are emitted by libddcutil to implement this functionality. Other than that, Plasma's use of DDC commands is the same as before.

It would be great if you could use `ddcutil dumpvcp` to compare whether any monitor settings (a.k.a. VCP feature values) are different before and after the undesired change. Realistically though, if this comparison doesn't show an obvious mistake on our part, you may have to create a ticket on the GitHub issue tracker of upstream ddcutil.

Note that as a workaround, you can disable the use of ddcutil in Plasma/PowerDevil by setting an enviroment variable POWERDEVIL_NO_DDCUTIL=1. For more details, see the PowerDevil README: https://invent.kde.org/plasma/powerdevil/-/blob/master/README.md#troubleshooting-ddcci-monitor-brightness-controls
Comment 7 Bug Janitor Service 2024-08-14 03:46:53 UTC
🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!
Comment 8 Bug Janitor Service 2024-08-29 03:47:59 UTC
🐛🧹 This bug has been in NEEDSINFO status with no change for at least 30 days. Closing as RESOLVED WORKSFORME.