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Layus

Member

Registered: 2012-04-30

Posts: 12

Udev misses some (HDMI) plug/unplug events

When I monitor udev events while plugging and unplugging my external hdmi monitor, only some random events are reported.
It should be noted that I use a DVI screen with an HDMI cable and a small adapter between the cable and the screen.

Here is a sample session :

$ udevadm monitor                     
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing
KERNEL - the kernel uevent

KERNEL[140907.961440] change   /devices/pci0000:00/0000:00:02.0/drm/card0 (drm) [plug or unplug; other event missing]
UDEV  [140907.962541] change   /devices/pci0000:00/0000:00:02.0/drm/card0 (drm)

[missed 7 unplug/plug cycles]

KERNEL[141838.431577] change   /devices/pci0000:00/0000:00:02.0/drm/card0 (drm) [unplug]
UDEV  [141838.432396] change   /devices/pci0000:00/0000:00:02.0/drm/card0 (drm)
KERNEL[141838.448023] change   /devices/pci0000:00/0000:00:02.0/drm/card0 (drm) [plug]
UDEV  [141838.448853] change   /devices/pci0000:00/0000:00:02.0/drm/card0 (drm)

[more missed cycles]

I also dumped a full event :

$ udevadm monitor --udev --kernel --property  
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing
KERNEL - the kernel uevent

KERNEL[142298.213473] change   /devices/pci0000:00/0000:00:02.0/drm/card0 (drm)
ACTION=change
DEVNAME=/dev/dri/card0
DEVPATH=/devices/pci0000:00/0000:00:02.0/drm/card0
DEVTYPE=drm_minor
HOTPLUG=1
MAJOR=226
MINOR=0
SEQNUM=2896
SUBSYSTEM=drm

UDEV  [142298.214231] change   /devices/pci0000:00/0000:00:02.0/drm/card0 (drm)
ACTION=change
DEVNAME=/dev/dri/card0
DEVPATH=/devices/pci0000:00/0000:00:02.0/drm/card0
DEVTYPE=drm_minor
HOTPLUG=1
ID_FOR_SEAT=drm-pci-0000_00_02_0
ID_PATH=pci-0000:00:02.0
ID_PATH_TAG=pci-0000_00_02_0
MAJOR=226
MINOR=0
SEQNUM=2896
SUBSYSTEM=drm
TAGS=:seat:uaccess:
USEC_INITIALIZED=42

I have no idea where to continue investigating.
Should I look for bugs in the kernel modules ? In udev ?
Could it be that my setup makes it impossible to detect some events ?

Thanks !

freebullets

Member

Registered: 2011-11-10

Posts: 31

Re: Udev misses some (HDMI) plug/unplug events

I experience the same thing with my HP laptop. Udev sometimes detects the change, but sometimes it doesn't. If I open KDE Settings, the change is detected.

hxss

Member

Registered: 2017-10-17

Posts: 34

Re: Udev misses some (HDMI) plug/unplug events

same problem. I use keyboard fn-key for toggle displays.

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 19,791

Re: Udev misses some (HDMI) plug/unplug events

Closing this old thread.

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