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erjiang
Asked: 2010-12-01 10:02:19 +0800 CST

Configure udev to change permissions on USB HID device?

  • 772

I have a USB scale, a USB HID. Currently, when it is plugged in, the permissions only allow the superuser to access it. How can I configure udev to let anybody access this device? I have the vendor and product IDs, but I would like to match it based on the HID type instead.

Right now, I'm having trouble finding any existing rule that applies to this (I grepped for "hidraw" in /lib/udev/rules.d and /etc/udev/rules.d, among other things).

usb input-devices udev

5 Answers

  1. Best Answer

    Normally, this is done by adding to /etc/udev/rules.d a file maybe named 50-usb-scale.conf with contents like this:

    SUBSYSTEM=="usb", ATTR{idVendor}=="HEX1", ATTR{idProduct}=="HEX2", MODE="0666"

    Where HEX1 and HEX2 are replaced with the vendor and product id respectively.

    To match on the Interface type instead, you could try replacing ATTR{idVendor}=="HEX1", ATTR{idProduct}=="HEX2" with a match for bInterfaceClass being 03 (HID):

    SUBSYSTEM=="usb", ATTR{bInterfaceClass}=="03", MODE="0666"

    But be warned, that will catch mice and keyboards too.

    • 28

  2. Just for the summary:

    You may filter for:

    • idVendor
    • idProduct
    • serial

    And use:

    == Compare for equality.

    != Compare for inequality.

    = Assign a value to a key. Keys that represent a list are reset and only this single value is assigned.

    += Add the value to a key that holds a list of entries.

    := Assign a value to a key finally; disallow any later changes.

    You may give a specific device a specific new path in /dev/...
    Example:

    KERNEL=="hiddev*", ATTRS{idVendor}=="16c0", ATTRS{idProduct}=="05df", ATTRS{serial}=="1234567", GROUP="cdrom", OWNER="user28", MODE="0640", SYMLINK+="myhid"

    Results in:

    You can access the device via '/dev/hiddevx' or via '/dev/myhid' easyly, every user in group 'cdrom' may read from the device. Owner 'user28' may read and write.

    or simplest:

    KERNEL=="hiddev*", ATTRS{idVendor}=="16c0", MODE="0666"

    Results in: Every user may access every hiddevice from Vendor 0x16c0

    For details see: Docs

    • 7

  3. In case you need to change (like me) ttyACM0 permissions, this are my settings:

    KERNEL=="ttyACM0", MODE="0777"

    It failed when I tried to specify the vendor and product ID. I am not sure why.

    • 6

  4. If its a HIDRAW device, you have to 

    chmod 0666 /dev/hidrawX

    where X is the hid device number, e.g hidraw0. you can do 

    ls /dev/hid*

    to see a list :) Or just do 

    sudo chmod 0666 /dev/hidraw*

    to set for all hidraw devices, probably not recommended.

    • 3

  5. Ubuntu 18.04 update/clarification:

    Kees Cook's answer is close but requires 2 changes to work in 18.04 (the current release and only one I've tested this on).

    1. Find your idVendor and idProduct with lsusb.
      • This will be the 2 hex values after "ID", separated by a colon. I'm adding a scanner. lsusb gave me: 
        Bus 001 Device 011: ID 04b8:014a Seiko Epson Corp.
    2. As root add a file to /etc/udev/rules.d
      • Something like 50-usb-epsonscanner.rules
      • The extension must be ".rules"  
    3. In that file add:
      SUBSYSTEM=="usb", ATTRS{idVendor}=="04b8", ATTR{idProduct}=="014a", MODE="0666"
      But with your idVendor and idProduct hex values.
      • Note it's "ATTRS" not "ATTR".
    4. Re-login. No need to reboot.
    • 3