How to match a ttyUSBX device to a usb serial device

Question

option driver correctly matched USB ID and loads driver for this device. For example

# lsusb
Bus 001 Device 002: ID 19d2:0031 ONDA Communication S.p.A. ZTE MF636
Bus 001 Device 003: ID 12d1:14ac Huawei Technologies Co., Ltd.

It also creates ttyUSBX devices for managing the hardware

crw-rw---- 1 root uucp 188, 0 Jul  4 13:48 /dev/ttyUSB0
crw-rw---- 1 root uucp 188, 1 Jul  4 13:49 /dev/ttyUSB1
crw-rw---- 1 root uucp 188, 2 Jul  4 13:35 /dev/ttyUSB2
crw-rw---- 1 root uucp 188, 3 Jul  4 13:37 /dev/ttyUSB3
crw-rw---- 1 root uucp 188, 4 Jul  4 13:37 /dev/ttyUSB4
crw-rw---- 1 root uucp 188, 5 Jul  4 13:37 /dev/ttyUSB5
crw-rw---- 1 root uucp 188, 6 Jul  4 13:37 /dev/ttyUSB6
crw-rw---- 1 root uucp 188, 7 Jul  4 13:37 /dev/ttyUSB7

However, I have more then one usb serial devices and I want to know which ttyUSB is for which USBID. Ex. /dev/ttyUSB1 -> 19d2:0031

Do you know any point where I can get this information?

Answer 1

Have a look at the sysfs filesystem. An example for my USB serial:

$ lsusb
Bus 003 Device 016: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
$ ls -l /sys/bus/usb-serial/devices
lrwxrwxrwx 1 root root 0 Jul  4 17:37 ttyUSB0 -> ../../../devices/pci0000:00/0000:00:1c.0/0000:02:00.0/usb3/3-1/3-1:1.0/ttyUSB0
$ $ grep PRODUCT= /sys/bus/usb-serial/devices/ttyUSB0/../uevent
PRODUCT=67b/2303/300

As you can see, ttyUSB0 maps to 067b:2303 on my computer. An other locations worth exploring are /sys/class/tty/. Pay attention to symlinks.

Answer 2

You can try to see if your device(s) are registered under /dev/serial/by-id/

ls -l /dev/serial/by-id

These names should be consistent and will point (symlink) to the correct ttyUSBx

Answer 3

I had a similar problem.

Write this to /etc/udev/rules.d/50-usb.rules

SUBSYSTEM=="tty", ATTRS{idVendor}=="19d2", ATTRS{idProduct}=="0031", SYMLINK+="ONDA"
SUBSYSTEM=="tty", ATTRS{idVendor}=="12d1", ATTRS{idProduct}=="14ac", SYMLINK+="HUAWEI"

to the end. Reboot.

Now you can use /dev/ONDA to get to your ONDA device.

If you want non-root users to be able to use these, then add

, MODE="0666"

to the end of each line.

Answer 4

I would use udev and write some rules which create symlinks for the devices.

To get enough information to distinguish the devices try something like this for all devices:

$ udevadm info --query all --name /dev/ttyUSB0 --attribute-walk

Answer 5

The following commands will give me list of ttyUSB device names that are associated with 19d2:0016 (which is the "modem mode" id of a ZTE MF831 LTE stick, yours may differ.):

    for i in $(find -L /sys/bus/usb/devices/ -maxdepth 2 -name "ttyUSB*"); do
        egrep -i "v19d2p0016(.*)in02" $i/../modalias >/dev/null && echo "/dev/${i##*/}"
    done

This will loop through a list of files with filename ttyUSB*, including symlinks, in /sys/bus/usb/devices. Within the results we will search for a file named modalias and look for a string containing the vendor id "v" "19d2" and product id "p" 0016. If the output matches, we will echo a string prefixed with "/dev/" in front of the USB? name. Afaik the first or the usually the last (highest number) is the modem port for ZTE devices. You can echo the results to a file in /tmp/ and head -n1 or tail -n1 the lines accordingly. If you have hubs, you may probably need to increase maxdepth.

This isn't the most elegant way, but it will work on almost any Linux variant.