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My sysfs has details on current, voltage etc under the battery node /sys/class/power_supply/BATn. However, under the AC node, none of these details are available.

I'd like to know how to go about determining what the problem is,

  • Doesn't the hardware provide the data?
  • Do I lack a kernel module?
  • Some detail lacking in BIOS?
  • Any other questions that should be asked?

My kernel is 5.12.6 (archlinux)

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  • A friend reports the same on a ubuntu @ 5.8.0.
    – lash
    Jun 14 at 8:21
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Doesn't the hardware provide the data?

Usually, that's exactly the case. Usually even, because the hardware doesn't even sense that.

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  • 2
    Most PC power supplies do not report this as it would add cost and not much benefit - AC draw is just DC use multiplied byt the efficiency of the PSU, usually ~90% ish. Power failure (/PWRGOOD) is detected as the lower-voltage internal rail drops. High end server gear might do it but I suspect the main purpose of the AC node is for smart UPS units to report the status of the mains voltage - nearly all APC units can connect by one or more of USB, serial or network to tell connected machines about power failure, spikes, etc.
    – John U
    Jun 14 at 12:59

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