On Mar 27, 2014 8:48 AM, "Satz Klauer" <<a href="mailto:satzklauer@googlemail.com">satzklauer@googlemail.com</a>> wrote: > > So...hopefully this is really the udev mailing list... > > I use CentoOS 6.5, an embedded device that is connected via USB and > shows up as /dev/ttyACMx (in my case it is always /dev/ttyACM0). To > have it read/writable for everybody and to avoid the modem-manager is > accessing it I created following rule in > /etc/udev/rules.d/52-mydev.rules: > > SUBSYSTEM=="usb", ATTR{idVendor}=="1781", ATTR{idProduct}=="1ef0", > MODE="0666", GROUP="plugdev", ENV{ID_MM_DEVICE_IGNORE}="1" > > Unfortunately they are not working as expected, /dev/ttyACM0 is still > not world-read/writable and the modem-manager still comes in between. > > What I found meanwhile using udev-debug-output: the rule is used and > applied, at least for the mode 0666. But udev sets the permissions to > the USB endpoint path (something with /bus/usb/...) but not to the > device. > > So: how can I let udev change the permission of the device? And whyt > could be the reason why modem-manager still tries to use it? > > Any ideas and suggestions are welcome! udev sets permissions on the USB endpoint because that's what your rule matches – you have SUBSYSTEM="usb", you match against USB sysfs attributes, etc. The actual tty device node most likely has "tty" as subsystem – use `udevadm info /dev/ttyACM0` to see the subsystem and the ENV{} variables that you can match against, and let the rule check also attrs of _parent_ devices using ATTRS{} instead of ATTR{} (if these matches are necessary in the end; I think env matches will be simpler). -- Mantas Mikulėnas <<a href="mailto:grawity@gmail.com">grawity@gmail.com</a>>