40-libvirt-usb-hotplug.rules

ACTION=="bind", SUBSYSTEMS=="usb", RUN="/usr/local/sbin/libvirt-hotplug.py usb"

libvirt-usb-hotplug.py

#!/usr/bin/env python3

import libvirt
import xml.etree.ElementTree as ET
import sys
import os
import re

RE_HEX_SUFFIX = re.compile('([0-9a-fA-F]+)$')

def hex_suffix(s):
  match = RE_HEX_SUFFIX.search(s)
  if match == None:
    return ''
  return match.groups()[0]

def usage(bin):
  print("Usage: {} <bus>".format(bin))

if len(sys.argv) < 2:
  print("Too few arguments")
  usage(sys.argv[0])
  sys.exit(1)

bus = sys.argv[1]
if bus != 'usb':
  print('Sorry, atm only usb devices are supported')
  sys.exit(1)

if not 'ID_VENDOR_ID' in os.environ or \
   not 'ID_MODEL_ID' in os.environ:
  sys.exit()

vid = os.environ['ID_VENDOR_ID'].lower()
pid = os.environ['ID_MODEL_ID'].lower()

conn = libvirt.open(None)
if not conn:
  raise Exception("Failed to connect to libvirt")

def handle_dev_usb(hostdev):
  vendor = hostdev.find("./source/vendor")
  product = hostdev.find("./source/product")
  if vendor == None or product == None:
    print("Invalid XML, needs 'vendor' and 'product'")
    return False

  if not 'id' in vendor.attrib or not 'id' in product.attrib:
    return False

  candidate_vid = hex_suffix(vendor.attrib['id']).lower()
  candidate_pid = hex_suffix(product.attrib['id']).lower()

  return candidate_vid == vid and candidate_pid == pid

def hostdev_purge_address(dev):
  source = dev.find('./source')
  if source != None:
    address = source.find('./address')
    if address != None:
      source.remove(address)

# Iterate through active domains
for domid in conn.listDomainsID():
  dom = conn.lookupByID(domid)
  xml = ET.fromstring(dom.XMLDesc())

  # Retrieve all host devices on the bus
  hostdevs = xml.findall(".//hostdev[@type='{}']".format(bus))
  for dev in hostdevs:
    if handle_dev_usb(dev):
      print("Attaching device [{}:{}] to {}".format(vid, pid, dom.name()))
      devxml = ET.tostring(dev, encoding='unicode')
      dom.detachDevice(devxml)

      # Remove address node, libvirt will figure that one out by itself
      hostdev_purge_address(dev)
      devxml = ET.tostring(dev, encoding='unicode')
      dom.attachDevice(devxml)
      break