blob: 4a4d597592a18fbbc4d41491d3333a4d49a6843e [file] [log] [blame]
# Copyright 2018 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Collection of servod utilities."""
import os
import re
import usb
class ServodutilError(Exception):
"""General servoduil error class."""
class UsbHierarchy(object):
"""A helper class to analyze the sysfs hierarchy of USB devices."""
USB_SYSFS_PATH = '/sys/bus/usb/devices'
CHILD_RE = re.compile(r'\d+-\d+(\.\d+){1,}\Z')
BUS_FILE = 'busnum'
DEV_FILE = 'devnum'
def __init__(self):
# Get the current USB sysfs hierarchy.
def GetAllUsbDevices(vid_pid_list):
"""Return all associated USB devices which match the given VID/PID's.
vid_pid_list: List of tuple (vid, pid).
List of usb.core.Device objects.
all_devices = []
for vid, pid in vid_pid_list:
devs = usb.core.find(idVendor=vid, idProduct=pid, find_all=True)
if devs:
return all_devices
def GetUsbDevice(vid, pid, serial):
"""Given vendor id, product id, and serial return usb device object.
vid: vendor id
pid: product id
serial: serial name
usb.core.Device object if found otherwise None
ServodutilError: if more than one device are found with those attributes.
devices = UsbHierarchy.GetAllUsbDevices([(vid, pid)])
devs = []
for device in devices:
d_serial = usb.util.get_string(device, 256, device.iSerialNumber)
if d_serial == serial:
if len(devs) > 1:
raise ServodutilError('Found %d devices with |vid:%s|, |pid:%s|, '
'|serial:%s|. Should not happen.' % (len(devs),
return devs[0] if devs else None
def _ResolveUsbSysfsPath(path):
if not os.path.isabs(path):
path = os.path.join(UsbHierarchy.USB_SYSFS_PATH, path)
return path
def DevNumFromSysfs(sysfs_path):
path = UsbHierarchy._ResolveUsbSysfsPath(sysfs_path)
devfile = os.path.join(path, UsbHierarchy.DEV_FILE)
with open(devfile, 'r') as devf:
return int(
def BusNumFromSysfs(sysfs_path):
path = UsbHierarchy._ResolveUsbSysfsPath(sysfs_path)
busfile = os.path.join(path, UsbHierarchy.BUS_FILE)
with open(busfile, 'r') as busf:
return int(
def RefreshUsbHierarchy(self):
"""Walk through usb sysfs files and gather parent identifiers.
The usb sysfs dir contains dirs of the following format:
- 1-2
- 1-2:1.0
- 1-2.4
- 1-2.4:1.0
The naming convention works like so:
<roothub>-<hub port>[.port[.port]]:config.interface
We are only going to be concerned with the roothub, hub port and port.
We are going to create a hierarchy where each device will store the usb
sysfs path of its roothub and hub port. We will also grab the device's
bus and device number to help correlate to a usb.core.Device object.
We will walk through each dir and only match on device dirs
(e.g. '1-2.4') and ignore config.interface dirs. When we get a hit, we'll
grab the bus/dev and infer the roothub and hub port from the dir name
('1-2' from '1-2.4') and store the info into a dict.
The dict key will be a tuple of (bus, dev) and value be the sysfs path.
Dict of tuple (bus,dev) to sysfs path.
usb_hierarchy = {}
for usb_dir in os.listdir(self.USB_SYSFS_PATH):
if self.CHILD_RE.match(usb_dir):
usb_dir = os.path.join(self.USB_SYSFS_PATH, usb_dir)
# Remove last element to get to parent hub's location
parent = '.'.join(usb_dir.split('.')[:-1])
dev = UsbHierarchy.DevNumFromSysfs(usb_dir)
bus = UsbHierarchy.BusNumFromSysfs(usb_dir)
except IOError:
# This means no bus/dev files. Skip
usb_hierarchy[(bus, dev)] = (usb_dir, parent)
self._usb_hierarchy = usb_hierarchy
def GetParentPath(self, usb_device):
"""Return the USB sysfs path of the supplied usb_device's parent.
usb_device: usb.core.Device object.
SysFS path string of parent of the supplied usb device.
return self._usb_hierarchy.get((int(usb_device.bus), int(
def ShareSameHub(self, usb_servo, usb_candidate):
"""Check if the given USB device shares the same hub with servo v4.
usb_servo: usb.core.Device object of servo v4.
usb_candidate: usb.core.Device object of USB device canditate.
True if they share the same hub; otherwise, False.
usb_servo_parent = self.GetParentPath(usb_servo)
usb_candidate_parent = self.GetParentPath(usb_candidate)
if usb_servo_parent is None or usb_candidate_parent is None:
return False
# Check the hierarchy:
# internal hub <-- servo v4 mcu
# \--------- USB candidate
if usb_servo_parent == usb_candidate_parent:
return True
# Check the hierarchy:
# internal hub <-- servo v4 mcu
# \--------- external hub
# \--------- USB candidate
# Check having '.' to make sure it is one of the ports of the internal hub.
if usb_candidate_parent.startswith(usb_servo_parent + '.'):
return True
return False