Find the /sys/bus/usb/devices subdirectory for a device

usbsysfind

#!/usr/bin/python

""" Find the /sys/bus/usb/devices subdirectory for a device """

import argparse
import os
import sys

DEVICES_DIR="/sys/bus/usb/devices"


def parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument("--device", "-d", help="ID for the device in the form abcd:abcd", required=True)
    return parser.parse_args()


def die(msg):
    print >> sys.stderr, msg
    sys.exit(1)


def contents(filename):
    with open(filename, "r") as handle:
        return handle.read()


def chomp(s, ending=None):
    if ending is None:
        ending = "\n"
    assert s.endswith(ending)
    return s[:-len(ending)]


def main():
    options = parse_args()
    if len(options.device) != 9 or options.device[4] != ":":
        die("Expected device value in the form xxxx:xxxx")

    id_vendor = options.device[:4].lower()
    id_product = options.device[-4:].lower()

    for dirname_proper in os.listdir(DEVICES_DIR):
        dirname = os.path.join(DEVICES_DIR, dirname_proper)
        if not os.path.isdir(dirname):
            continue
        if not all(os.path.exists(os.path.join(dirname, x)) for x in ("idProduct", "idVendor")):
            continue
        cur_id_vendor  = chomp(contents(os.path.join(dirname, "idVendor"))).lower()
        if cur_id_vendor != id_vendor:
            continue
        cur_id_product  = chomp(contents(os.path.join(dirname, "idProduct"))).lower()
        #print "%s:%s -> %s" % (cur_id_product, cur_id_vendor, dirname_proper)
        if cur_id_product == id_product:
            print dirname
            break
    else:
        die("Device %s not found" % options.device)


if __name__ == "__main__":
    main()