8

I have some trouble understanding how the udev device attributes from different parent devices are evaluated in a rule. I want to write a rule for a specific serial usb device (HUAWEI Modem), with a attribute walk as follows:

$ udevadm info --attribute-walk --name=/dev/ttyUSB0

  looking at device '/devices/platform/bcm2708_usb/usb1/1-1/1-1.3/1-1.3:1.0/ttyUSB0/tty/ttyUSB0':
    KERNEL=="ttyUSB0"
    SUBSYSTEM=="tty"
    DRIVER==""

  looking at parent device '/devices/platform/bcm2708_usb/usb1/1-1/1-1.3/1-1.3:1.0/ttyUSB0':
    KERNELS=="ttyUSB0"
    SUBSYSTEMS=="usb-serial"
    DRIVERS=="generic"
    ATTRS{port_number}=="0"

  looking at parent device '/devices/platform/bcm2708_usb/usb1/1-1/1-1.3/1-1.3:1.0':
    KERNELS=="1-1.3:1.0"
    SUBSYSTEMS=="usb"
    DRIVERS=="usbserial_generic"
    ATTRS{bInterfaceClass}=="ff"
    ATTRS{bInterfaceSubClass}=="02"
    ATTRS{bInterfaceProtocol}=="01"
    ATTRS{bNumEndpoints}=="03"
    ATTRS{supports_autosuspend}=="1"
    ATTRS{bAlternateSetting}==" 0"
    ATTRS{bInterfaceNumber}=="00"

  looking at parent device '/devices/platform/bcm2708_usb/usb1/1-1/1-1.3':
    KERNELS=="1-1.3"
    SUBSYSTEMS=="usb"
    DRIVERS=="usb"
    ATTRS{bDeviceSubClass}=="00"
    ATTRS{bDeviceProtocol}=="00"
    ATTRS{devpath}=="1.3"
    ATTRS{idVendor}=="12d1"
    ATTRS{speed}=="480"
    ATTRS{bNumInterfaces}==" 4"
    ATTRS{bConfigurationValue}=="1"
    ATTRS{bMaxPacketSize0}=="64"
    ATTRS{busnum}=="1"
    ATTRS{devnum}=="5"
    ATTRS{configuration}==""
    ATTRS{bMaxPower}=="500mA"
    ATTRS{authorized}=="1"
    ATTRS{bmAttributes}=="80"
    ATTRS{bNumConfigurations}=="1"
    ATTRS{maxchild}=="0"
    ATTRS{bcdDevice}=="0001"
    ATTRS{avoid_reset_quirk}=="0"
    ATTRS{quirks}=="0x0"
    ATTRS{version}==" 2.00"
    ATTRS{urbnum}=="4561"
    ATTRS{ltm_capable}=="no"
    ATTRS{manufacturer}=="HUAWEI"
    ATTRS{removable}=="removable"
    ATTRS{idProduct}=="1506"
    ATTRS{bDeviceClass}=="00"
    ATTRS{product}=="HUAWEI MOBILE"

In order to identify this device I tried to use following udev rule:

ACTION=="add", KERNEL=="ttyUSB[0-9]*", SUBSYSTEMS=="usb", ATTRS{bInterfaceNumber}=="00", ATTRS{idVendor}=="12d1", ATTRS{idProduct}=="1506", RUN+="/usr/bin/systemctl start modem_dialer"

but unfortunately I cannot use the attribute ATTRS{bInterfaceNumber}=="00" from the interface device and the attributes ATTRS{idVendor}=="12d1", ATTRS{idProduct}=="1506" from the physical device together. Using either of them works fine, but when using them together the rule does not work anymore.

Am I missing anything regarding the usage of attributes from different parent devices together in one rule? Is there any other reason why using the attributes from different parents might be a problem?

By the way, the distro is Arch Linux ARM.

5

To use attributes from multiple parents, you need to use multiple rules and GOTO. Something like this.

SUBSYSTEMS=="usb", ATTRS{bInterfaceNumber}!="00", GOTO="huawei_end"
ACTION=="add", KERNEL=="ttyUSB[0-9]*", SUBSYSTEMS=="usb", ATTRS{idVendor}=="12d1", ATTRS{idProduct}=="1506", RUN+="/usr/bin/systemctl start modem_dialer"
LABEL="huawei_end"

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.