How to identify multiple USB-serial adapters under

Question

I am reading data from multiple identical USB-serial adapters under Ubuntu 10.1.

On occasion, their /dev/tty path changes (eg if other USB devices are connected on startup).

I need a way of repeatedly referring to the same adapter through any such changes.

The devices all have the same serial numbers, according to udevadm.

I think the most likely option is to identify an adapter by which port it is connected to (they don't get moved around).

I can find all sorts of interesting /dev paths that might work, but despite all the discussion about udev online, I can't locate a definitive statement about whether some of these paths are static if the device is plugged into a static port.

Answer 1

There is a solution. It's better late then never ;)

Use the following udev rule to map /dev/ttyUSB{?} devices into the /dev/usb-ports/%bus_id-%port_id link.

Here is my /etc/udev/rules.d/usb-parse-devpath.rules:

ACTION=="add", KERNEL=="ttyUSB[0-9]*", PROGRAM="/etc/udev/rules.d/usb-parse-devpath.pm %p", SYMLINK+="usb-ports/%c"

And the usb-parse-devpath.pm script:

#!/usr/bin/perl -w

@items = split("/", $ARGV[0]);
for ($i = 0; $i < @items; $i++) {
    if ($items[$i] =~ m/^usb[0-9]+$/) {
        print $items[$i + 1] . "\n";
        last;
    }
}

As you can see this helps us to create named links to /dev/ttyUSB{?} devices and place them at /dev/usb-ports in the following format: bus_id-port_id.

For example, the next command gives me the following:

$ udevadm info --query=path --name=/dev/ttyUSB0
/devices/pci0000:00/0000:00:1d.1/usb3/3-1/3-1:1.0/ttyUSB0/tty/ttyUSB0

So, the bus_id is 3 and port_id is 1 and now I have following in my /dev/usb-ports:

$ ls -al /dev/usb-ports
lrwxrwxrwx  1 root root   10 Май 12 00:26 3-1 -> ../ttyUSB0

Regards.

Answer 2

Much like Ilya Matvejchikov's answer, a good solution is to add udev rules to do what you want with the device. Like you, I was having a similar problem. I had a UPS on a USB-to-multi-serial adapter and occasionally the system would switch around the /dev/tty numbers.

My solution was to create a rule to match the type of device by driver and port, then create a symbolic link to the port to which my UPS was attached. I used NUT to monitor the UPS, which was always plugged into the same physical port.

# File contents of /etc/udev/rules.d/75-nut-ups.rules
# Create /dev/nut-ups0 to use as a persistent serial device that can be used
# reliably by nut to communicate with a UPS attached to the system.
# The UPS is attached to the first port of a MosSemiconductor dual USB
# serial adapter.
KERNELS=="ttyUSB*", SUBSYSTEMS=="usb-serial", DRIVERS=="moschip7720", ATTRS{port_number}=="0", SYMLINK+="nut-ups0"

Now I configure NUT to always use a constant /dev/nut-ups0, as the serial port and the rule takes care of mapping properly when the usb-serial device is recognized.

You can use the lsusb command to find out the actual device name to use in the rule when it's plugged in.

Answer 3

Look with $ udevadm info -n /dev/ttyUSB0 -a which port your USB device is plugged in. The variable KERNELS of one of the parent devices should be something like KERNELS=="1-1.2:1.0".

Create a udev rule:

SUBSYSTEM=="tty", KERNELS=="1-1.2:1.0", SYMLINK+="ttyUSB42"
SUBSYSTEM=="tty", KERNELS=="1-1.3:1.0", SYMLINK+="usb-serial"

and trigger udev

$ udevadm trigger

Answer 4

I have many USB to Serial devices with each many ports and the solutions mentioned above did not quite did it for me.

The USB "KERNEL" was not enough in my case, but I found the port number.

I am aware that what I'm proposing now might be considered an insane hack, but it works for me..
for now..

I would actually be pleased to see a more elegant suggestion that accomplish something similar..

So... Based on the previous answer form Ilya Matveychikov

File: /etc/udev/rules.d/usb-parse-devpath.sh

#!/bin/bash

DEVNUM=$(echo "${1}" | rev | cut -d'/' -f4 | rev | tr -d '-' | tr -d '.' | tr -d ':')
PORTNUM=$(/sbin/udevadm info -a --path=${1} | grep "ATTRS{port_number}" | head -1 | cut -d'"' -f2)
PRODUCT=$(/sbin/udevadm info -a --path=${1} | grep "ATTRS{product}" | head -1 | cut -d'"' -f2 | tr -d '/' | tr ' ' '_')

NEWID="ttyUSB_${PRODUCT}_${DEVNUM}${PORTNUM}"

#echo "${NEWID} :: $1" >> /tmp/DEBUG_udev.txt

echo "$NEWID"

And File: /etc/udev/rules.d/99-usb-serial.rules

ACTION=="add", KERNEL=="ttyUSB[0-9]*", PROGRAM="/etc/udev/rules.d/usb-parse-devpath.sh %p", SYMLINK+="TTYUSBs/%c"

The result look something like this:

# ls -l /dev/TTYUSBs

lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_435100 -> ../ttyUSB20
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_435101 -> ../ttyUSB21
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_435102 -> ../ttyUSB22
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_435103 -> ../ttyUSB23
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_435104 -> ../ttyUSB24
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_435105 -> ../ttyUSB25
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_435106 -> ../ttyUSB26
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_435107 -> ../ttyUSB27
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_436100 -> ../ttyUSB28
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_436101 -> ../ttyUSB29
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_436102 -> ../ttyUSB30
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_436103 -> ../ttyUSB31
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_436104 -> ../ttyUSB32
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_436105 -> ../ttyUSB33
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_436106 -> ../ttyUSB34
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport416_436107 -> ../ttyUSB35
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport4_4341100 -> ../ttyUSB38
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport4_4341101 -> ../ttyUSB39
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport4_4342100 -> ../ttyUSB36
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport4_4342101 -> ../ttyUSB37
lrwxrwxrwx. 1 root root 10 Jan  5 18:46 ttyUSB_Edgeport8_421100 -> ../ttyUSB2
lrwxrwxrwx. 1 root root 10 Jan  5 18:46 ttyUSB_Edgeport8_421101 -> ../ttyUSB3
lrwxrwxrwx. 1 root root 10 Jan  5 18:46 ttyUSB_Edgeport8_422100 -> ../ttyUSB4
lrwxrwxrwx. 1 root root 10 Jan  5 18:46 ttyUSB_Edgeport8_422101 -> ../ttyUSB5
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport8_423100 -> ../ttyUSB18
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Edgeport8_423101 -> ../ttyUSB19
lrwxrwxrwx. 1 root root 10 Jan  5 18:46 ttyUSB_Edgeport8_424100 -> ../ttyUSB0
lrwxrwxrwx. 1 root root 10 Jan  5 18:46 ttyUSB_Edgeport8_424101 -> ../ttyUSB1
lrwxrwxrwx. 1 root root 10 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_431100 -> ../ttyUSB6
lrwxrwxrwx. 1 root root 10 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_431101 -> ../ttyUSB7
lrwxrwxrwx. 1 root root 10 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_431102 -> ../ttyUSB8
lrwxrwxrwx. 1 root root 10 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_431103 -> ../ttyUSB9
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_432100 -> ../ttyUSB10
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_432101 -> ../ttyUSB11
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_432102 -> ../ttyUSB12
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_432103 -> ../ttyUSB13
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_433100 -> ../ttyUSB14
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_433101 -> ../ttyUSB15
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_433102 -> ../ttyUSB16
lrwxrwxrwx. 1 root root 11 Jan  5 18:46 ttyUSB_Keyspan_USA-49WG_433103 -> ../ttyUSB17

Answer 5

I too was searching this topic for a way to find which physical USB device was assigned/connected to a logical /dev device name. So, after some trial and error, this is what worked best for me:

See what logical ttyUSBx devices exist (where x is 0, 1, 2...):

$ ls /dev

Show bus and device numbers for all usb-serial adapters:

$ lsusb 

Finally, use:

$ udevadm info --name=ttyUSBx --attribute-walk | grep num  

Now inspect the udevadm output to match the logical device name to the actual physical device. Here my listing when I did it:

$ lsusb
Bus 002 Device 005: ID 0403:6001 Future Technology Devices International, Ltd FT232 USB-Serial     (UART) IC
Bus 002 Device 004: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
Bus 002 Device 002: ID 80ee:0021  
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

$ udevadm info --name=ttyUSB0 --attribute-walk | grep num
    ATTRS{port_number}=="0"
    ATTRS{urbnum}=="812"
    ATTRS{busnum}=="2"
    ATTRS{devnum}=="5"
    ATTRS{urbnum}=="115"
    ATTRS{busnum}=="2"
    ATTRS{devnum}=="1"
    ATTRS{numa_node}=="-1"

$ udevadm info --name=ttyUSB1 --attribute-walk | grep num
    ATTRS{port_number}=="0"
    ATTRS{urbnum}=="465"
    ATTRS{busnum}=="2"
    ATTRS{devnum}=="4"
    ATTRS{urbnum}=="115"
    ATTRS{busnum}=="2"
    ATTRS{devnum}=="1"
    ATTRS{numa_node}=="-1"

So, in my case, ttyUSB0 is associated with the device on bus2, device5, which is the Future Technology Devices International USB to Serial Adapter; and likewise, ttyUSB1 is associated with the device on bus2, device4, which is the Prolific Technology, Inc. USB to Serial adapter.

And as has been pointed out, the command:

$ usb-devices

Will get you the same info in a one-line manner. I thought I'd post the details that helped me learn how the stuff worked behind the scenes...

Hope that was helpful :)

Answer 6

The devices all have the same serial numbers [..]

The usb-parse-devpath.pm addresses this by using the bus and port id of the adapter.