pyusb power

Usage

usage: power.py [-h] [-m [MOD ...]] {cycle,off,on} id

Powers off/on usb devices by id

positional arguments:
  {cycle,off,on}        action to perform: power-cycle, off or on
  id                    usb device id in the form 'idVendor:idProduct', each id is a hex number from 0 to ffff, e.g., '123:abcd'

options:
  -h, --help            show this help message and exit
  -m [MOD ...], --mod [MOD ...]
                        kernel module(s) to unload before the action, and to load back after the action

Note the script needs to be run as root.

Motivation

I wrote this python script after I accidentally discovered a workaround, using hub-ctrl fork by Yi Yu, to make ethernet port on my Razer Core X Chroma usable on a laptop running Arch Linux. The fix was to power off the ports, to which the ethernet controller is (internally) connected to, then power them on again. I wanted to do this without hardcoding the hub bus/device, which isn't possible with hub-ctrl, so I turned to using pyusb to find devices by vendor and product id, and ported the usb_control_msg() from hub-ctrl to power off/on the discovered devices. I also noticed that power-cycling the ethernet adapter creates a new network interface called eth0, leaving the old predictably named one hanging dead. A workaround that helps is to unload the ax88179_178a kernel module before the power-cycling and then load it back again. Hence, I added an option to do this with the same script too. Now I just run

python power.py cycle 0b95:1790 -m ax88179_178a

on system boot, and ethernet finally works.

Dependencies

The script has the following dependencies:

• libusb-1.0-0
• libusb-0.1-4
• pyusb >= 1.1.0

It uses both libusb1 and libusb0 backends for two reasons:

1. libusb0 doesn't implement the get_parent method that is used to find the hub, to which a device is connected to
2. In my tests, only using libusb-0.1-4 to execute power off/on control messages yielded the desired results. Neither libusb1, nor libusb-compat did the trick.

Arch Linux

libusb-1.0-0 and pyusb:

sudo pacman -Sy libusb python-pyusb

libusb-0.1-4 has to be installed via AUR, https://aur.archlinux.org/packages/libusb0, e.g., with yay:

yay -Sy libusb0

Ubuntu

Newer Ubuntu distros (at least, starting from 22.04) have pyusb==1.2.1 in the official [universe] repositories, and so all the dependencies can be installed with apt:

sudo apt update
sudo apt install libusb-1.0-0 libusb-0.1-4 python3-usb

If you're running an older Ubuntu distro, e.g., 20.04 has pyusb==1.0.2, you can install pyusb from PyPI:

sudo apt update
sudo apt install libusb-1.0-0 libusb-0.1-4 python3-pip
sudo python3 -m pip install pyusb