[Bug 1980991] Re: /usr/sbin/on_ac_power incorrectly reporting ac power status

[Launchpad Bug Tracker]

** Merge proposal linked:
   https://code.launchpad.net/~dgadomski/ubuntu/+source/powermgmt-base/+git/powermgmt-base/+merge/471623

-- 
You received this bug notification because you are a member of Ubuntu
Sponsors, which is subscribed to the bug report.
https://bugs.launchpad.net/bugs/1980991

Title:
  /usr/sbin/on_ac_power incorrectly reporting ac power status

Status in powermgmt-base package in Ubuntu:
  Fix Released
Status in powermgmt-base source package in Focal:
  Confirmed
Status in powermgmt-base source package in Jammy:
  Confirmed
Status in powermgmt-base source package in Kinetic:
  Won't Fix
Status in powermgmt-base source package in Lunar:
  Won't Fix
Status in powermgmt-base source package in Mantic:
  Won't Fix
Status in powermgmt-base source package in Noble:
  Confirmed
Status in powermgmt-base source package in Oracular:
  Fix Released
Status in powermgmt-base package in Debian:
  New

Bug description:
  Thank you @kevintate for the original bug report.

  [Impact]

  Currently there is an issue with the ac_on_power script where it thinks that USB-c ports with devices plugged in to them are plugged in to power. This is because the script does not check first if these usb-c ports are in sink or source mode first.
  The solution is to check /sys/class/typec/* for the mode these usb ports are in, and ignore them if none of them are running in source mode.

  [Test Plan]

  On a device with a USB-c port (it does not matter if the port can be
  used for powering the device or not) run the following test:

  1. Install the patched version of on_ac_power

  2. run: $ on_ac_power

  3. check the return value: $ echo $?

  compare the return value with the actual state of the machine. If the
  machine is not plugged in to power, you should expect 0 as the return
  code.

  If the machine is plugged in then the return code should be 1.

  If you receive 255 as an return code then the script was unable to
  determine the power profile of the machine and is related to the
  kernel not exposing enough information to user space. Consumers of
  on_ac_power generally consider such a return code as the machine being
  plugged in to power.

  [Where problems could occur]

  * the script could still incorrectly return the state of power of the
  machine, specially if the kernel incorrectly advertises a usbc port to
  be in a different mode then it is in.

  
  [Original Description]
  Good afternoon, folks.

  I believe I discovered a bug in the /usr/sbin/on_ac_power script. I
  have a Dell OptiPlex 5090 host that has an entry in
  /sys/class/power_supply for "ucsi-source-psy-USBC000:001". I believe
  this is the USB-C power delivery port on the front of the chassis. The
  issue I'm encountering is that /usr/sbin/on_ac_power is exiting with
  code 1 which states: (1 (false) if not on AC power) when that isn't
  the case.

  This looks to be because of the ucsi-source-psy-USBC000:001 entry
  reporting the "online" status as 0, presumably because nothing is
  currently connected to that USB-C port.

  This causes /usr/sbin/on_ac_power to incorrectly report that the
  machine isn't connected to AC power and causes other utilities like
  unattended-upgrades to quit when using the default configuration since
  it believes the machine isn't connected to AC power.

  There is a workaround with unattended-upgrades where you can specify
  it to run regardless of if AC power is connected, but as more and more
  chassis implement power-delivery USB-C ports I foresee this becoming
  more of an issue.

  I'm not sure if it's anything to look into, but I figured I would
  share my findings. Please let me know if you have any questions or if
  I can provide any additional information, troubleshooting, or testing.

  Thanks!
  -Kevin

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/powermgmt-base/+bug/1980991/+subscriptions