Bug 389660

Summary:	Lot of "org.kde.powerdevil.backlighthelper[PID]: QDBusArgument: read from a write-only object" in journal log
Product:	[Unmaintained] Powerdevil	Reporter:	CnZhx <zhx>
Component:	general	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED FIXED
Severity:	minor	CC:	accounts+bugs.kde, avolkov, justin.zobel, karl
Priority:	NOR
Version First Reported In:	5.11.95
Target Milestone:	---
Platform:	Debian stable
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description CnZhx 2018-01-30 22:36:08 UTC

I am using a laptop with openSUSE Tumbleweed. Recently I noticed there are a lot of messages like following in the journal log,
```
Jan 30 22:18:07 ostw org.kde.powerdevil.backlighthelper[28142]: QDBusArgument: read from a write-only object
Jan 30 22:18:07 ostw org.kde.powerdevil.backlighthelper[28142]: QDBusArgument: read from a write-only object
Jan 30 22:18:07 ostw org.kde.powerdevil.backlighthelper[28142]: QDBusArgument: read from a write-only object
Jan 30 22:18:07 ostw dbus-daemon[1133]: [system] Successfully activated service 'org.kde.powerdevil.backlighthelper'
Jan 30 22:19:11 ostp dbus-daemon[1133]: [system] Activating service name='org.kde.powerdevil.backlighthelper' requested by ':1.44' (uid=1000 pid=2615 comm="/usr/lib64/libexec/org_kde_powerdevil -session 101") (using servicehelper)
Jan 30 22:19:11 ostw org.kde.powerdevil.backlighthelper[28587]: QDBusArgument: read from a write-only object
Jan 30 22:19:11 ostw org.kde.powerdevil.backlighthelper[28587]: QDBusArgument: read from a write-only object
Jan 30 22:19:11 ostw org.kde.powerdevil.backlighthelper[28587]: QDBusArgument: read from a write-only object
Jan 30 22:19:11 ostw dbus-daemon[1133]: [system] Successfully activated service 'org.kde.powerdevil.backlighthelper'
```

When using `journalctl -f` to track the events, I found this kind of messages pops up when the system reducing and restoring the screen backlight.

This is not a problem but I think the three duplicated messages in the middle are not necessary to normal user and may cause confusion. However, I do not know whether they are related to something bigger.

Could anyone look into this and do something like either suppressing the messages or fixing the problem when it is necessary?

Comment 1 Florian Jacob 2018-12-04 09:25:41 UTC

I can confirm this bug. It is still present in Plasma 5.13.4, and is happening on NixOS as well.

Comment 2 Karl 2019-10-24 19:46:54 UTC

Bug still alive in:

libpowerdevilcore2                            4:5.14.5-1
libpowerdevilui5                              4:5.14.5-1

"read from a write-only object" sounds like a bug -  didn't detect the hardware type?

Comment 3 Karl 2019-10-24 19:48:35 UTC

Oct 24 14:37:19 pocket dbus-daemon[550]: [system] Activating service name='org.kde.powerdevil.backlighthelper' requested by ':1.349' (uid=1001 pid=4920 comm="/usr/lib/x86_64-linux-gnu/libexec/org_kde_powerdev") (using servicehelper)
Oct 24 14:37:19 pocket org.kde.powerdevil.backlighthelper: QDBusArgument: read from a write-only object
Oct 24 14:37:19 pocket org.kde.powerdevil.backlighthelper: QDBusArgument: read from a write-only object
Oct 24 14:37:19 pocket org.kde.powerdevil.backlighthelper: QDBusArgument: read from a write-only object
Oct 24 14:37:19 pocket dbus-daemon[550]: [system] Successfully activated service 'org.kde.powerdevil.backlighthelper'
Oct 24 14:38:34 pocket dbus-daemon[550]: [system] Activating service name='org.kde.powerdevil.backlighthelper' requested by ':1.349' (uid=1001 pid=4920 comm="/usr/lib/x86_64-linux-gnu/libexec/org_kde_powerdev") (using servicehelper)

Comment 4 Alexander Volkov 2020-07-16 14:07:14 UTC

It was probably fixed by https://invent.kde.org/libraries/polkit-qt-1/-/commit/fb1667ac9a5437b4784d2806a3e816cbdbe404a5

Comment 5 Justin Zobel 2020-11-12 21:51:02 UTC

Can you please confirm if this issue was fixed after the commit mentioned in Comment 4.

I'm setting status to "needsinfo" pending your response, please change back to "reported" or "resolved" when you respond, thanks.

Comment 6 Bug Janitor Service 2020-11-27 04:34:03 UTC

Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

If you have already provided the requested information, please
mark the bug as REPORTED so that the KDE team knows that the bug is
ready to be confirmed.

Thank you for helping us make KDE software even better for everyone!

Comment 7 CnZhx 2020-12-07 01:54:37 UTC

Sorry for the late response. This bug was fixed. 

As a proof, the journal now reports,
```
Dec 07 09:20:13 ostp dbus-daemon[716]: [system] Activating service name='org.kde.powerdevil.backlighthelper' requested by ':1.63' (uid=1000 pid=2656 comm="/usr/lib64/libexec/org_kde_powerdevil ") (using servicehelper)
Dec 07 09:20:13 ostp dbus-daemon[716]: [system] Successfully activated service 'org.kde.powerdevil.backlighthelper'
```