Powertop shows "ghost" USB connection draining battery..

[yangmusa]

I'm not sure quite in which sub-forum to post this question, but Hardware seems a good bet. Please let me know if I should move it..

Several weeks ago I plugged in an external USB cd/dvd writer. Powertop still shows this near the top of the processes consuming power - usually somewhere from a few hundred mW up to about 1 W*. Typically my laptop uses 3-10 W total, so IF it's true then 1 W is a considerable unnecessary drain. (*Yes, the power draw fluctuates. This makes it seem less like a phantom process and maybe more like some real issue with the USB bus?)

Questions:

• Is there a way to tell if the USB port is actually drawing power?

• If so, how to I make it stop?

• If the USB port is not drawing power, is there a way to get the phantom process to stop showing up?

Thanks!

[DAMIEN1307]

when you click on "disks" found in the menu, does it still show that besides the HD and cd/dvd drive, that there is also a USB drive even though none is plugged in, and does it show when highlighted that it is still mounted?...DAMIEN

[yangmusa]

when you click on "disks" found in the menu, does it still show that besides the HD and cd/dvd drive, that there is also a USB drive even though none is plugged in, and does it show when highlighted that it is still mounted?...DAMIEN

No, there's no sign of it in Nemo.

Attaching image of Powertop, so you can see what I'm seeing:

Powertop-USBCDRW.png

EDIT: not to distract from my initial question, but does 5 watts seem too high for wifi? I'm running on one antenna because the connector broke, so I suspect the card may be drawing more power to compensate for a weaker antenna?

[DAMIEN1307]

i did not ask if it was found in nemo...i asked if it was found in "disks"...DAMIEN

[yangmusa]

i did not ask if it was found in nemo...i asked if it was found in "disks"...DAMIEN

My bad. No, it doesn't appear in Disks either.

I think I resolved this, though the technical detail of why/how eludes me. I mentioned my problem to a friend who mainly uses Windows. Based on my description of the problem, he said in Windows he would have issued a command to rescan the USB bus & devices. I did a search for doing that in Linux, and came up with:

Code: Select all

udevadm trigger

The short story is: this worked. No more ghost devices! Noticeable improvement in battery life!

[yangmusa]

Bah! The ghost-device is back! udevadm trigger no longer seems to get rid of it

[Drugwash]

Is there a way to tell if the USB port is actually drawing power?

Not that it will actually solve any issue you may be having but as a straight answer to your question: yes, there is. A device called USB Charger Doctor.
Here is a random example that happens to be the very same model I'm using with my notebook: link
However this other one may prove more useful: link
Hope it helps.