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wildfowl

Banned

Registered: 2014-10-16

Posts: 82

udev will only trigger after suspend or resume

Has anyone seen this before?

I'm trying to set up a battery discharge trigger with udev.

udev won't update normally but will only update after a resume from suspend.

wildfowl

Banned

Registered: 2014-10-16

Posts: 82

Re: udev will only trigger after suspend or resume

The kernel is not sending power_supply/BAT0/uevent on a frequent basis to report battery level but will only send it where there's a significant change in some state.

Is there any way to get the kernel to report the battery level a little more regularly through uevents?

wildfowl

Banned

Registered: 2014-10-16

Posts: 82

Re: udev will only trigger after suspend or resume

Does anyone have any suggestions?

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,659

Re: udev will only trigger after suspend or resume

Which kernel are you using and what are the make and model of the computer?  (Just a WAG, but I am thinking HP)

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wildfowl

Banned

Registered: 2014-10-16

Posts: 82

Re: udev will only trigger after suspend or resume

I've tried the kernels 4.1.0, 4.1.6 (Liquorix) and 4.2.0-rc8.

I have tried this on several different HP machines and under all these system the kernel is reporting changes in power percentages through uevents.

On another similar system I am using now (quite similar to HP), the battery level is updated on a frequent basis which can be seen through acpi or upower but the kernel isn't sending a uevent on a frequent basis for some reason.

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,659

Re: udev will only trigger after suspend or resume

Darn,  I had nothing but trouble with my HP with ACPI system in general.  Everything power related would block when the system was running under load.  Reads from /sys related to power would not return until the system returned to lower loads/temperatures.   I thought your issue might be related.  I found that the 4.2.0 rc4 improved the situation dramatically.  But, you've tried rc8.     Have you considered trying the lts kernel?

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Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
The shortest way to ruin a country is to give power to demagogues.— Dionysius of Halicarnassus
---
How to Ask Questions the Smart Way

wildfowl

Banned

Registered: 2014-10-16

Posts: 82

Re: udev will only trigger after suspend or resume

I haven't tried any LTS kernel. I consider 4.1.0 to support legacy hardware quite well.

Generally I have found HP to be quite well supported in terms of power management and most other components. I have a habit of using my own pm schemes together with maintaining oversight of the precise modules in use. None of those ready made pm daemons or utilities.

On this occasion however, I wish to understand a little more about the mechanics under which the kernel sends uevents and why that sometimes it doesn't.

I sent an email to the linux-pm list but haven't heard anything back.

wildfowl

Banned

Registered: 2014-10-16

Posts: 82

Re: udev will only trigger after suspend or resume

If I do:

echo change | sudo tee /sys/class/power_supply/*/uevent

or even:

sudo udevadm trigger --verbose --subsystem-match=power_supply

then this will trigger the correct event. I'm not understanding why this can't (or won't) be done automatically by the kernel or upower?

Is upower the culprit?