Adding a kernel task, as the /dev/input/js0 is created by the kernel driver (usbhid) itself. udev does not create device nodes, it just adds additional properties, runs extra programs on the device nodes, etc.
So cases a/ vs. b/ is interesting -- in both cases you get three HID devices, just that in the wireless USB dongle case the "hid-generic" driver grabs them as it just sees the transceiver, while in the wired USB case it's the "logitech" driver as it sees the devices directly. input_id only actually sees a joystick with the wireless transceiver (see a1), there you see that the js0 device claims to have tons of absolute axes: capabilities/abs decoded bit map: bit 0: FFFFFF01000701FF while in the b/ case capabilities/abs is zero, i. e. no axes. input_id is here: https://github.com/systemd/systemd/blob/master/src/udev/udev-builtin- input_id.c In test_pointers() you see that has_joystick_axes_or_buttons is determined by buttons/axes which are typical for a joystick: /* joysticks don't necessarily have buttons; e. g. * rudders/pedals are joystick-like, but buttonless; they have * other fancy axes */ has_joystick_axes_or_buttons = test_bit(BTN_TRIGGER, bitmask_key) || test_bit(BTN_A, bitmask_key) || test_bit(BTN_1, bitmask_key) || test_bit(ABS_RX, bitmask_abs) || test_bit(ABS_RY, bitmask_abs) || test_bit(ABS_RZ, bitmask_abs) || test_bit(ABS_THROTTLE, bitmask_abs) || test_bit(ABS_RUDDER, bitmask_abs) || test_bit(ABS_WHEEL, bitmask_abs) || test_bit(ABS_GAS, bitmask_abs) || test_bit(ABS_BRAKE, bitmask_abs); This needs to be checked against the decoded capabilities/key (for the buttons) and capabilities/abs (for the absolute axes), the numerical values of the evdev constants are in /usr/include/linux/input.h. The above is just a heuristic of course which has been refined over time, and might need more refinement. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1458631 Title: udev: /dev/input/js0 is created but no joystick attached To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1458631/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
