2

I'm trying to use udev to give relevant names a USB-serial device but I'm having no luck.

    # lsusb -d 04e2:1412 -v

    Bus 004 Device 028: ID 04e2:1412 Exar Corp. 
    Device Descriptor:
      bLength                18
      bDescriptorType         1
      bcdUSB               2.00
      bDeviceClass          239 Miscellaneous Device
      bDeviceSubClass         2 Common Class
      bDeviceProtocol         1 Interface Association
      bMaxPacketSize0        64
      idVendor           0x04e2 Exar Corp.
      idProduct          0x1412 
      bcdDevice            0.02
      iManufacturer           0 
      iProduct                0 
      iSerial                 0 
      bNumConfigurations      1
      Configuration Descriptor:
        bLength                 9
        bDescriptorType         2
        wTotalLength          141
        bNumInterfaces          4
        bConfigurationValue     1
        iConfiguration          0 
        bmAttributes         0xa0
          (Bus Powered)
          Remote Wakeup
        MaxPower               94mA
        Interface Association:
          bLength                 8
          bDescriptorType        11
          bFirstInterface         0
          bInterfaceCount         2
          bFunctionClass          2 Communications
          bFunctionSubClass       2 Abstract (modem)
          bFunctionProtocol       0 None
          iFunction               0 
        Interface Descriptor:
          bLength                 9
          bDescriptorType         4
          bInterfaceNumber        0
          bAlternateSetting       0
          bNumEndpoints           1
          bInterfaceClass         2 Communications
          bInterfaceSubClass      2 Abstract (modem)
          bInterfaceProtocol      1 AT-commands (v.25ter)
          iInterface              0 
          CDC Header:
            bcdCDC               1.10
          CDC ACM:
            bmCapabilities       0x06
              sends break
              line coding and serial state
          CDC Union:
            bMasterInterface        0
            bSlaveInterface         1 
          CDC Call Management:
            bmCapabilities       0x01
              call management
            bDataInterface          1
          Endpoint Descriptor:
            bLength                 7
            bDescriptorType         5
            bEndpointAddress     0x85  EP 5 IN
            bmAttributes            3
              Transfer Type            Interrupt
              Synch Type               None
              Usage Type               Data
            wMaxPacketSize     0x0040  1x 64 bytes
            bInterval               2
        Interface Descriptor:
          bLength                 9
          bDescriptorType         4
          bInterfaceNumber        1
          bAlternateSetting       0
          bNumEndpoints           2
          bInterfaceClass        10 CDC Data
          bInterfaceSubClass      0 Unused
          bInterfaceProtocol      0 
          iInterface              0 
          Endpoint Descriptor:
            bLength                 7
            bDescriptorType         5
            bEndpointAddress     0x01  EP 1 OUT
            bmAttributes            2
              Transfer Type            Bulk
              Synch Type               None
              Usage Type               Data
            wMaxPacketSize     0x0040  1x 64 bytes
            bInterval               0
          Endpoint Descriptor:
            bLength                 7
            bDescriptorType         5
            bEndpointAddress     0x81  EP 1 IN
            bmAttributes            2
              Transfer Type            Bulk
              Synch Type               None
              Usage Type               Data
            wMaxPacketSize     0x0040  1x 64 bytes
            bInterval               0
        Interface Association:
          bLength                 8
          bDescriptorType        11
          bFirstInterface         2
          bInterfaceCount         2
          bFunctionClass          2 Communications
          bFunctionSubClass       2 Abstract (modem)
          bFunctionProtocol       0 None
          iFunction               0 
        Interface Descriptor:
          bLength                 9
          bDescriptorType         4
          bInterfaceNumber        2
          bAlternateSetting       0
          bNumEndpoints           1
          bInterfaceClass         2 Communications
          bInterfaceSubClass      2 Abstract (modem)
          bInterfaceProtocol      1 AT-commands (v.25ter)
          iInterface              0 
          CDC Header:
            bcdCDC               1.10
          CDC ACM:
            bmCapabilities       0x06
              sends break
              line coding and serial state
          CDC Union:
            bMasterInterface        2
            bSlaveInterface         3 
          CDC Call Management:
            bmCapabilities       0x01
              call management
            bDataInterface          3
          Endpoint Descriptor:
            bLength                 7
            bDescriptorType         5
            bEndpointAddress     0x86  EP 6 IN
            bmAttributes            3
              Transfer Type            Interrupt
              Synch Type               None
              Usage Type               Data
            wMaxPacketSize     0x0040  1x 64 bytes
            bInterval               2
        Interface Descriptor:
          bLength                 9
          bDescriptorType         4
          bInterfaceNumber        3
          bAlternateSetting       0
          bNumEndpoints           2
          bInterfaceClass        10 CDC Data
          bInterfaceSubClass      0 Unused
          bInterfaceProtocol      0 
          iInterface              0 
          Endpoint Descriptor:
            bLength                 7
            bDescriptorType         5
            bEndpointAddress     0x02  EP 2 OUT
            bmAttributes            2
              Transfer Type            Bulk
              Synch Type               None
              Usage Type               Data
            wMaxPacketSize     0x0040  1x 64 bytes
            bInterval               0
          Endpoint Descriptor:
            bLength                 7
            bDescriptorType         5
            bEndpointAddress     0x82  EP 2 IN
            bmAttributes            2
              Transfer Type            Bulk
              Synch Type               None
              Usage Type               Data
            wMaxPacketSize     0x0040  1x 64 bytes
            bInterval               0
    Device Status:     0x0000
      (Bus Powered)

The udev rules I'm trying are:

    KERNEL=="ttyUSB[0-9]*", SUBSYSTEMS=="usb", ATTRS{bInterfaceNumber}=="01", ATTRS{idVendor}=="04e2", ATTRS{idProduct}=="1412",  ACTION=="add", SYMLINK+="test_USB0"
    KERNEL=="ttyUSB[0-9]*", SUBSYSTEMS=="usb", ATTRS{bInterfaceNumber}=="01", ATTRS{idVendor}=="04e2", ATTRS{idProduct}=="1412",  ACTION=="add", SYMLINK+="test_USB1"
    KERNEL=="ttyUSB[0-9]*", SUBSYSTEMS=="usb", ATTRS{bInterfaceNumber}=="02", ATTRS{idVendor}=="04e2", ATTRS{idProduct}=="1412",  ACTION=="add", SYMLINK+="test_USB2"
    KERNEL=="ttyUSB[0-9]*", SUBSYSTEMS=="usb", ATTRS{bInterfaceNumber}=="03", ATTRS{idVendor}=="04e2", ATTRS{idProduct}=="1412",  ACTION=="add", SYMLINK+="test_USB3"

When I used only the first udev rule without the bInterfaceNumber attribute, like so:

    KERNEL=="ttyUSB[0-9]*", SUBSYSTEMS=="usb", ATTRS{idVendor}=="04e2", ATTRS{idProduct}=="1412",  ACTION=="add", SYMLINK+="test_USB0"

It works ok. I can see the symbolic link /dev/test_USB0 created which points to /dev/ttyUSB0 but what about the other ttyUSB devices created when I plugged in this USB-serial device?

That was why I wanted to use the bInterfaceNumber attribute but when I put it in, nothing happened and it seemed to completely bypass my rule.

Can anyone help me with this?

2
  • have you found a solution for this? I have the exact same problem but adding ATTRS{serial} to my rules. They work perfectly without that, but as soon as I add that they stop working. I need to use ATTRS{serial} because I have several devices that have all other info the same and this is the only attribute that differentiate them.
    – m4l490n
    Nov 7, 2016 at 4:51
  • @m4l490n I know it's been years since you commented here but you can take a look at my answer below that may give you a hint.
    – yaobin
    Oct 13 at 1:27

2 Answers 2

1

You can use ENV{ID_USB_INTERFACE_NUM}, defined in /lib64/udev/rules.d/60-persistent-serial.rules

Use udevadm test to check what environment available.

1

It looks like the rule didn't work because you mixed attributes from different parent devices.

The article Writing udev rules mentions this case in the section "udevinfo":

You may have noted the use of colour in the above examples. This is to demonstrate that while it is legal to combine the attributes from the device in question and a single parent device, you cannot mix-and-match attributes from multiple parent devices - your rule will not work.

The problem with lsusb -v is it lists the information of the device itself and its parent devices together so you can't tell whether the attributes come from the same parent device or from multiple parent devices.

However, if you use udevadm info (on Ubuntu) or udevinfo (as the author used), you should be able to print the hierarchy of the devices. In the article, the author gave the following example:

# udevinfo -a -p /sys/block/sda

  looking at device '/block/sda':
    KERNEL=="sda"
    SUBSYSTEM=="block"
    ATTR{stat}=="  128535     2246  2788977   766188    73998   317300  3132216  5735004        0   516516  6503316"
    ATTR{size}=="234441648"
    ATTR{removable}=="0"
    ATTR{range}=="16"
    ATTR{dev}=="8:0"

  looking at parent device '/devices/pci0000:00/0000:00:07.0/host0/target0:0:0/0:0:0:0':
    KERNELS=="0:0:0:0"
    SUBSYSTEMS=="scsi"
    DRIVERS=="sd"
    ATTRS{ioerr_cnt}=="0x0"
    ATTRS{iodone_cnt}=="0x31737"
    ATTRS{iorequest_cnt}=="0x31737"
    ATTRS{iocounterbits}=="32"
    ATTRS{timeout}=="30"
    ATTRS{state}=="running"
    ATTRS{rev}=="3.42"
    ATTRS{model}=="ST3120827AS     "
    ATTRS{vendor}=="ATA     "
    ATTRS{scsi_level}=="6"
    ATTRS{type}=="0"
    ATTRS{queue_type}=="none"
    ATTRS{queue_depth}=="1"
    ATTRS{device_blocked}=="0"

  looking at parent device '/devices/pci0000:00/0000:00:07.0':
    KERNELS=="0000:00:07.0"
    SUBSYSTEMS=="pci"
    DRIVERS=="sata_nv"
    ATTRS{vendor}=="0x10de"
    ATTRS{device}=="0x037f"

So the following rule would work because:

  • SUBSYSTEM=="block" comes from the device itself.
  • Both SUBSYSTEMS=="scsi" and ATTRS{model}=="ST3120827AS" come from the same parent device /devices/pci0000:00/0000:00:07.0/host0/target0:0:0/0:0:0:0.
SUBSYSTEM=="block", SUBSYSTEMS=="scsi", ATTRS{model}=="ST3120827AS", NAME="my_hard_disk"

However, as the author said, the following rule would not work because ATTRS{model}=="ST3120827AS" and DRIVERS=="sata_nv" come from two different parent devices:

SUBSYSTEM=="block", ATTRS{model}=="ST3120827AS", DRIVERS=="sata_nv", NAME="my_hard_disk"

So I would suggest the OP to check the device hierarchy using udevadm info (or udevinfo) command to see if you are mixing attributes from different parent devices.

I happen to be working on a USB device today and the output of udevadm info (I'm using Ubuntu 18.04) showed me that the vendor ID and product ID belong to one parent device, but bInterfaceNumber belongs to another parent device. Therefore, when your rule only contained the vendor ID and product ID, it was the case of "single parent device" so it would work. When you added bInterfaceNumber into the rule, and if your USB device has a similar device hierarchy as my USB device, the rule would not work because it was a case of mixing multiple parent devices.

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