I wanted to power off a USB device. Searching in Google for “power off usb” returns different results but I didn’t succeed in any of the suggestions (Linux version 3.2.0).
I asked on the linux-usb mailing list (question, see one of the relevant answers (from Alan Stern). In short: not possible. When using a USB hub it’s then maybe possible -some models only-. The answer includes a link to a small program to try to disable the port. I could disable the port, but the device had still power.
I still didn’t want to give up. I remembered that I bought, 2 years ago, a USB relay. Actually that one could be used, as it says, with 220VAC/10A, so I could power on a heating or some big device.
I did a bit of very bad-done hardware work: I “broke” a USB cable, got the red inner-cable to pass through the relay. Then using one USB port I control the relay and I can switch on and off the other USB device like I initially wanted.
As you can see in the photo I broke the shield too much -because a confusion that wasn’t directly related to the project-. Still, it works well with my dumb device and other devices.