Udev rules for a device with multiple interfaces

udevusb

So, I'm delving into udev and running into an issue.

I think that I understand the basic premise (please correct me if i'm wrong). Device is attached either due to your system booting up or sometime afterwards. Udev goes through all the rules looking for matches. once it finds a match, it executes whatever actions were requested, and continues going down the list of rules until it gets to the last one. Then it starts off on the next device.

Now, I have a usb device that creates 2 interfaces. When I attach it, i get both an can0 and can1 when I look in /sys/class/net/. But in /dev, there is only one entry for this under /dev/bus/usb/002/00X.

Now, here is where my problem comes. I want to name each of these interfaces something specific. I know that one always comes up before the other. If i do nothing, they get named can0 and can1. If I put a udev rule in, the first one that comes up gets renamed properly, but looking at the dmesg logs, the second one errs out because the kernel name is also can0 (since there is no can1).

How would one get around this? udevadm doesn't help since there is only one device listed in /dev, so it seems that I can't differentiate them by attributes.

output of lsusb -v below:

Bus 001 Device 011: ID 0c72:0011 PEAK System 
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        64
  idVendor           0x0c72 PEAK System
  idProduct          0x0011 
  bcdDevice            0.00
  iManufacturer           1 PEAK-System Technik GmbH
  iProduct                2 PCAN-USB Pro FD
  iSerial                 0 
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength          111
    bNumInterfaces          2
    bConfigurationValue     1
    iConfiguration          4 Config00
    bmAttributes         0x80
      (Bus Powered)
    MaxPower              240mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           6
      bInterfaceClass         0 (Defined at Interface level)
      bInterfaceSubClass      0 
      bInterfaceProtocol      0 
      iInterface              5 PCAN-USB Pro FD CAN
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x01  EP 1 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 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     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x02  EP 2 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        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     0x03  EP 3 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       0
      bNumEndpoints           6
      bInterfaceClass         0 (Defined at Interface level)
      bInterfaceSubClass      0 
      bInterfaceProtocol      0 
      iInterface              6 PCAN-USB Pro FD LIN
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x84  EP 4 IN
        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     0x04  EP 4 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     0x85  EP 5 IN
        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     0x05  EP 5 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     0x86  EP 6 IN
        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     0x06  EP 6 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
Device Qualifier (for other device speed):
  bLength                10
  bDescriptorType         6
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        64
  bNumConfigurations      1
Device Status:     0x0000
  (Bus Powered)

Best Answer

As seen in lsusb -v, your interfaces have different names. This can be additionally checked by

udevadm info -a -p $(udevadm info -q path -n can0)
udevadm info -a -p $(udevadm info -q path -n can1)

Therefore you can use ATTR{interface} to distinguish them.

SUBSYSTEM=="usb", ATTRS{idVendor}=="0c72", ATTRS{idProduct}=="0011", ATTR{interface}=="PCAN-USB Pro FD CAN"

Note that above we use specific combination of ATTR and ATTRS keys that matters because we look for values in current or current and parent device, see http://www.reactivated.net/writing_udev_rules.html.

If interfaces names are the same then they can be distinguished by ATTR{bInterfaceNumber}.

Related Solutions

Fixed udev rules for USB modems

After some discussion in chat it appears that that symlinks already exist in /dev/serial/by-path/ and will work.

List all udev rules (e.g. for a device)

If you use:

udevadm monitor

you get an entry for each action taken by KERNEL and UDEV. Typically add, change, remove. If you include the --property option:

udevadm monitor --property

You will get a listing of what properties are used.

As one can test udev rules with udevadm:

udevadm test $(udevadm info -q path -n <device>)

one could test out something as this:

udevadm test $(udevadm info -q path -n <device>) 2>&1 | \
sed -n 's/.* \(\/[^ ]*\)\.rules:\([0-9]\+\)/\1.rules \2/p' | \
while read -r f n; do printf "%03d:%-50s " $n "$f"; sed -n ${n}p $f; done

but not sure how reliable this is. Anyhow, using e.g. video1 for <device> that could yield something like:

031:/lib/udev/rules.d/50-udev-default.rules            SUBSYSTEM=="video4linux", GROUP="video"
007:/lib/udev/rules.d/60-persistent-v4l.rules          IMPORT{program}="v4l_id $devnode"
009:/lib/udev/rules.d/60-persistent-v4l.rules          SUBSYSTEMS=="usb", IMPORT{builtin}="usb_id"
010:/lib/udev/rules.d/60-persistent-v4l.rules          KERNEL=="video*", ENV{ID_SERIAL}=="?*", SYMLINK+="v4l/by-id/$env{ID_BUS}-$env{ID_SERIAL}-video-index$attr{index}"
016:/lib/udev/rules.d/60-persistent-v4l.rules          IMPORT{builtin}="path_id"
017:/lib/udev/rules.d/60-persistent-v4l.rules          ENV{ID_PATH}=="?*", KERNEL=="video*|vbi*", SYMLINK+="v4l/by-path/$env{ID_PATH}-video-index$attr{index}"
015:/lib/udev/rules.d/73-seat-late.rules               TAG=="uaccess", ENV{MAJOR}!="", RUN{builtin}+="uaccess"
006:/etc/udev/rules.d/83-webcam.rules                  KERNEL=="video[0-9]", SUBSYSTEMS=="usb", ATTRS{idVendor}=="0c45", SYMLINK+="video-webcam1"

But guess looking at the test as a whole is better. Also note the message:

This program is for debugging only, it does not run any program specified by a RUN key. It may show incorrect results, because some values may be different, or not available at a simulation run.

You can also set

udev_log="debug"

in udev.conf and restart udev (reload udev) to get a somewhat more verbose output.

Best Answer

Related Solutions

Fixed udev rules for USB modems

List all udev rules (e.g. for a device)

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