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I'm attempting to write a udev rule that triggers when my laptop power cable is plugged in, however I'm having some odd issues with it triggering multiple times, on both plugging and unplugging.

First, I get the name of the device:

$ udevadm monitor --subsystem-match power_supply

I happen to know the name of the subsystem already, but it doesn't actually matter. I then plug in the power cable.

KERNEL[771.036377] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:08/PNP0C09:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
KERNEL[771.553813] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:08/PNP0C09:00/ACPI0003:00/power_supply/AC (power_supply)
UDEV  [771.603337] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:08/PNP0C09:00/ACPI0003:00/power_supply/AC (power_supply)
UDEV  [771.791301] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:08/PNP0C09:00/PNP0C0A:00/power_supply/BAT0 (power_supply)

From this I can see there are 4 events, 2 of which belong to the BAT0 device and 2 the AC device.
Then I look at the attributes of the AC device to see what I can trigger off of.

$ udevadm info -a /sys/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:08/PNP0C09:00/ACPI0003:00/power_supply/AC

looking at device '/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:08/PNP0C09:00/ACPI0003:00/power_supply/AC':
KERNEL=="AC"
SUBSYSTEM=="power_supply"
DRIVER==""
ATTR{SUBSYSTEM}=="power_supply"
ATTR{POWER_SUPPLY_NAME}=="AC"
ATTR{POWER_SUPPLY_ONLINE}=="1"

looking at parent device '/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:08/PNP0C09:00/ACPI0003:00':
KERNELS=="ACPI0003:00"
SUBSYSTEMS=="acpi"
DRIVERS=="ac"
ATTRS{SUBSYSTEM}=="acpi"
ATTRS{DRIVER}=="ac"
ATTRS{MODALIAS}=="acpi:ACPI0003:"
ATTRS{USEC_INITIALIZED}=="3654374"
ATTRS{ID_VENDOR_FROM_DATABASE}=="The Linux Foundation"

looking at parent device '/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:08/PNP0C09:00':
KERNELS=="PNP0C09:00"
SUBSYSTEMS=="acpi"
DRIVERS=="ec"
ATTRS{SUBSYSTEM}=="acpi"
ATTRS{DRIVER}=="ec"
ATTRS{MODALIAS}=="acpi:PNP0C09:"
ATTRS{USEC_INITIALIZED}=="3588332"
ATTRS{ID_VENDOR_FROM_DATABASE}=="The Linux Foundation"

looking at parent device '/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:08':
KERNELS=="device:08"
SUBSYSTEMS=="acpi"
DRIVERS==""
ATTRS{SUBSYSTEM}=="acpi"

looking at parent device '/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00':
KERNELS=="PNP0A08:00"
SUBSYSTEMS=="acpi"
DRIVERS==""
ATTRS{SUBSYSTEM}=="acpi"
ATTRS{MODALIAS}=="acpi:PNP0A08:PNP0A03:"
ATTRS{USEC_INITIALIZED}=="3301031"
ATTRS{ID_VENDOR_FROM_DATABASE}=="The Linux Foundation"

looking at parent device '/devices/LNXSYSTM:00/LNXSYBUS:00':
KERNELS=="LNXSYBUS:00"
SUBSYSTEMS=="acpi"
DRIVERS==""
ATTRS{SUBSYSTEM}=="acpi"
ATTRS{MODALIAS}=="acpi:LNXSYBUS:"
ATTRS{USEC_INITIALIZED}=="3246891"
ATTRS{ID_VENDOR_FROM_DATABASE}=="The Linux Foundation"

looking at parent device '/devices/LNXSYSTM:00':
KERNELS=="LNXSYSTM:00"
SUBSYSTEMS=="acpi"
DRIVERS==""
ATTRS{SUBSYSTEM}=="acpi"
ATTRS{MODALIAS}=="acpi:LNXSYSTM:"
ATTRS{USEC_INITIALIZED}=="3107859"
ATTRS{ID_VENDOR_FROM_DATABASE}=="The Linux Foundation"

From this, trying to be as specific as possible, using attributes from the device itself as well as the parents I construct this rule:

ACTION=="change"
SUBSYSTEM=="power_supply"
DRIVERS=="ac"
ATTR{POWER_SUPPLY_NAME}=="AC"
ATTR{POWER_SUPPLY_ONLINE}=="1"
RUN+="/usr/bin/bash /home/josh/scripts/udev_sleep.sh"

Upon saving it and unplugging/replugging my laptop, I find that the script has ran 10's of times. Is there any way to trace why this is happening when the monitor only showed 4 events (all but one of which shouldn't have matched anyway?)

However perhaps there is a more general problem, as I find the rule triggers even if obviously unmatching conditions are contained within it, such as

ACTION=="change"
SUBSYSTEM=="Not even the right subsystem!"
DRIVERS=="ac"
ATTR{POWER_SUPPLY_NAME}=="Totally Fake Name"
ATTR{POWER_SUPPLY_ONLINE}=="Definitely not right"
RUN+="/usr/bin/bash /home/josh/scripts/udev_sleep.sh"

I'm guessing that there is something wrong with how I'm matching things, does it not work how I thought? I did read the udev man page and all examples online seem to follow a similar pattern.

  • 3
    this may be completely stupid (I hate udev & I'm on a phone) but weren't udev rules supposed to be separated by commas and written on the same line (or multiple lines terminated by a backslash line continuation)? – mosvy Feb 10 at 18:55
  • Try adding comma + backslash at the end of each line but the last RUN+="...". (The stupid web interface of this silly website won't let me enter them in a comment) – mosvy Feb 10 at 19:04
  • @mosvy Oh silly me, that was indeed the issue. I think I misread a part of the man page on that bit. Thanks. – JoshuaO Feb 10 at 22:29

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