Bug 486072

Created attachment 168894 [details]
ddcutil interrogate output

Please find the `ddcutil interrogate` output attached for further investigation. The display is currently connected via an HDMI cable.
Unfortunately in the moment I don't have a DP cable at hand for testing.

Does it still happen in Plasma 6.1.3 or later?

Can check in a few weeks again.

Logged in remotely with Wireguard + krdc, upgraded, rebooted and tested: Nope, still broken unfortunately!

When you adjust the slider and it does nothing, does `kscreen-doctor -o` say that the monitor's brightness is at the level you specified?

There's no info about any brightness:
```
kscreen-doctor -o
Output: 1 HDMI-A-1
        enabled
        connected
        priority 1
        HDMI
        Modes:  0:1920x1080@60*!  1:1920x1080@75  2:1920x1080@60  3:1920x1080@60  4:1920x1080@50  5:1600x1200@60  6:1680x1050@60  7:1280x1024@75  8:1280x1024@60  9:1440x900@75  10:1440x900@60  11:1280x960@60  12:1280x800@60  13:1152x864@75  14:1280x720@60  15:1280x720@60  16:1280x720@60  17:1280x720@50  18:1152x720@60  19:1024x768@75  20:1024x768@60  21:832x624@75  22:800x600@75  23:800x600@60  24:720x576@50  25:720x576@50  26:720x480@60  27:720x480@60  28:720x480@60  29:720x480@60  30:640x480@75  31:640x480@60  32:640x480@60  33:640x480@60  34:720x400@70  35:1280x1024@60  36:1024x768@60  37:1280x800@60  38:1920x1080@60  39:1600x900@60  40:1368x768@60  41:1280x720@60
        Geometry: 0,0 1920x1080
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: incapable
        RgbRange: unknown
        HDR: incapable
        Wide Color Gamut: incapable
        ICC profile: none
        Color profile source: sRGB
```

journalctl 
```
org_kde_powerdevil[6220]: dh=Display_Handle[i2c-0: fd=31], Replacing adjusted sleep multiplier 0,50 with 1.00 for SE_POST_WRITE or SE_POST_SAVE_SETTINGS
```

Ok, so KWin correctly thinks you don't have monitor brightness control, but Powerdevil disagrees.

The issue remains now on Fedora 41 with Plasma 6.2.2, but there's now no longer any log output when moving the slider, neither in journalctl nor in dmesg. 

Could it be detected that brightness changing doesn't work with powerdevil and fallback to a software overlay?
If not, could an option be added? The broken state right now, is a bit unfortunate. :)

Additionally resolving bug #495248 would also enhance the UX in this regard.

I've tested it again with

Operating System: Fedora Linux 41
KDE Plasma Version: 6.2.3
KDE Frameworks Version: 6.8.0
Qt Version: 6.8.0
Kernel Version: 6.11.7-300.fc41.x86_64 (64-bit)
Graphics Platform: Wayland

now with both HDMI and DP cable there's no brightness change but on slider release it logs
```
rg_kde_powerdevil[2978]: dh=Display_Handle[i2c-3: fd=32], Replacing adjusted sleep multiplier 0,10 with 1.00 for SE_POST_WRITE or SE_POST_SAVE_SETTINGS
```

*** Bug 489397 has been marked as a duplicate of this bug. ***

Are you still able to reproduce the issue with Plasma 6.3.5 and ddcutil 2.2.0 or later?

🐛🧹 ⚠️ 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!

🐛🧹 This bug has been in NEEDSINFO status with no change for at least 30 days. Closing as RESOLVED WORKSFORME.

Just happend the opportunity to test it again. Updated to Plasma 6.4.2 and Frameworks 6.15.0 and Kernel 6.15.6:

The slider has still no effect. Even when I uncheck "Use DDC" in kscreen it still doesn't  do anything, neither does the brightness slider in kscreen itself.

(In reply to postix from comment #16)
> when I uncheck "Use DDC" in kscreen it
> still doesn't  do anything, neither does the brightness slider in kscreen
> itself.

I tried it again a few hours later, un-check + apply, and now the software overlay works. How weird. But when re-checking the ddc checkbox and applying, the software overlay is still used. Looks like the config doesn't get applied correctly.

It started happening to me too, I believe it worked some weeks ago.
I had HDR enabled, tried the brightness slider and it used software dimming.
Found the new option for DDC/CI brightness, it was enabled, I tried with the options both disabled and enabled and it had no effect.
Then I tried disabling HDR and the brightness slider stopped working.
I set the brightness to half using "ddcutil setvcp 0x10 50" and it worked.
Then I ran "ddcutil interrogate" and didn't understand much.
After the two ddcutil commands I tried again with HDR disabled and it worked.
I re-enabled HDR and it fell back to software dimming!
But with "ddcutil setvcp 0x10 50" it correctly sets the monitor's brightness even with HDR enabled.

Here's the ddcutil detect + system info, LMK if you need more or to use my system for live debugging.

[The first is a DVI monitor connected via an HDMI adapter]
Invalid display 
   I2C bus:  /dev/i2c-5
   DRM connector:           card1-HDMI-A-1
   EDID synopsis:
      Mfg id:               DEL - Dell Inc.
      Model:                DELL P190S
      Product code:         16475  (0x405b)
      Serial number:        P86NM22EA3NM
      Binary serial number: 1093881421 (0x41334e4d)
      Manufacture year:     2012,  Week: 7
   DDC communication failed

Display 1
   I2C bus:  /dev/i2c-8
   DRM connector:           card1-DP-2
   EDID synopsis:
      Mfg id:               GSM - Goldstar Company Ltd (LG)
      Model:                LG ULTRAGEAR
      Product code:         23629  (0x5c4d)
      Serial number:        305NTWG2Z969
      Binary serial number: 101969 (0x00018e51)
      Manufacture year:     2023,  Week: 5
   VCP version:         2.1


Operating System: Arch Linux 
KDE Plasma Version: 6.4.2
KDE Frameworks Version: 6.16.0
Qt Version: 6.9.1
Kernel Version: 6.15.6-zen1-1-zen (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 3800XT 8-Core Processor
Memory: 32 GiB of RAM (31.3 GiB usable)
Graphics Processor: AMD Radeon RX 6750 XT
Manufacturer: Micro-Star International Co., Ltd.
Product Name: MS-7C94
System Version: 1.0